ECOLOGY MD CONTROL
OF
DYSDERCUS CINGULATUS FABR. ,
Thesis submitted
for
The Degree of Doctor of Philosophy
in
ZOOLOGY
of
THE ALIGABH MUSLIM UNIVERSITY, ALIGARH
By
Islam Ahmad
Department of Zoology
Aligarh Muslim University, Aligarh
April, 1969 ECOLOGY AND CONTROL OF DYSDERCUS CiNGLLATUS FABR.
THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF FHILOSOPHY IN ZOOLOGY OF
THE ALIGARH MUSLIM UNtVERSSTY, ALJGARH
BY ISLAM AHMAD
Department of Zoology Aligarh Muslim University, Aligarh. APRIL, 1969 T859 I certify that "Ecology and Gont2?o3^f
Dysdercus clngulat-us Fabr.," is the original work of
Islam Ahmad and is suitable for submission for the award of the degree of Doctor of Philosophy of the Aligarh
Muslim University, Aligarh. This work has been done by the candidate under my supervision.
Nawab Hasan Khan
Professor, Department of Zoology, Aligarh Muslim University, Aligarh. CONTENTS
Page I. Introduction ... 1 V II. Economic importance .. 3
Part I. ECOLOGY
III. Ovipositlon
(1) General
(ii) Effects of environmental conditions on ovipositlon ...
IV. Eggs 14
(i) General features 14
(11) Effect of temperature and humidity on the hatching of the eggs 14
(ill) Extension of incubation period by refrigeration.. 16
V. Nymphs 22
(i) Rearing ... 22
(ii) Number and duration of nymphal instars 23
(ill) Description of various instars 23
VI. Adults ...... 32
(i) Seasonal abundance ... 32
(ii) Copulation ...... 34
(iii) Longevity ...... 36
(iv) Selection of adults for extended survival without food and water 39 Page VII. Effects of different plant foods on fecundity, fertility and development. 42
Part II. CONTROL
VIII. Reviev of Literature ... 47
IX. Sensitivity of Dysdercus cingulatus to DDTj BHG and aldrin as shown by dosage - mortality regression lines ... •••
X. DDT, BHC and aldrin tolerance in
Dysaercus cingulatus ••. 66
XI. Bionomics of normal and BHC-resistant strains 76
XII. Susceptibility levels of field populations 79
XIII. Chemical sterilization of Dysdercus cingulatus 81 XIV. Permanency of sterility effects of apholate, tepa and metepa in males and females of Dysdercus cingulatus —
XV. Mating vigour and sexual competitiveness of chemosterilized males., ... '93
XVI. Development of resistance to apholate 97
XVII. Conclusions ...... 100
XVIII. Summary ...
XIX. Acknowledgements ...... US
XX. References ... ••. ^^^ INTRODUCTION
The struggle between man and insects has been going on since the early days of history. Insects not only transmit serious disease pathogens among man and animals but also eat a considerable portion of our crops and do great damage by aiding in the spread and development of plant diseases. Man on his part has succeeded in conquering a good number of these pests but there still remained many destructive insects against which little progress has been made. Cotton stainers are one of these.
The red cotton bug, Dysdercus cingulatus is a well known pest of cotton in India. Both the nymphs and the adults suck the sap from the leaves and green cotton bolls and when the latter open they attack the young oily seeds rendering them unfit for sowing. The yellow excreta of the bugs stains the lint and the species has also been reported to introduce
Nematospora gossypil into the bolls. But inspite of all its vile to human economy, our knowledge of the ecology and control of this insect is fragmentary and very little has been accomplished with respect to its control.
The present work was undertaken with two objects in view. First, to investigate the effects of environmental factors influencing the activities of D. cingulatus at various - 10 -
stages of its life, and second, to find out if it can be controlled effectively by the use of chemicals that have been employed against other related pests, in attempt has also been made to study the phenomena of insecticide resistance in this species and to find out if BHC selection pressure has any effect on the bionomics of the in-sect.
The eff^iency<^f the commonly used aziridine compounds, apholate, tepa and metepa as chemosterilants of D. cingulatus has also been evaluated. ,
^ For the sake of convenience^the findings have been presented in two parts. Part I deals with studies on the ecology of D. cingulatus while in part II tests conducted to determine the sensitivity of the red cotton bug to insecticides and the sterility effects produced by the chemosterilants have been described. - 10 -
ECONOMIC IMPORTANCE
Members of the family Pyrrhocoridae (Hemiptera)
are usually brightly coloured, moderately sized, robust
insects having four segmented antennae and three jointed
tarsi. They are world wide iti distribution and^nol: only
attack a number of plants belonging to the families
Malvaceae, Graminae, Sterculisiceae, Cruciferae, Rutaceae
and Cucurbitaceae but also feed on other organisms
including members of their own family. Antilochus cocqueberti
is a voracious feeder on Dysd.^rcus cingulatus and the
tenacity with which it sucks the body fluid of the host
is evident from the fact that the predator remains deeply
thrust into the body of the host even when its proboscis
is chopped off (Pradhan and M^non, 1942). Dlndymus rubiginosus
feeds on Oreta extensa and Lavana Candida. Another
carnivorous species is p. sanguineous which feeds on flies
and termites.
The cotton stainers belonging to the genus Dvsdercus
can be easily distinguished f^om other members of the
family as the apical angle of hemelytra is somewhat acute
and there is no hamus in cell of the hind wing. They are
important pests of cotton in different countries of the world/except the United Arab Hepublic, Mesopotamia,
Turkestan and the northern part of^the Merican cot'ton belt (VJhitfield, 1933). - 10 -
The red cotton bug, D. clngulatus is a serious pest of cotton in India. It is found in Uttar fradesh, Bihar,
Madhya Pradesh, Bombay, Tamil Nadu, West Bengal and the
Punjab (Sohi, 1964). Besides cotton it attacks Bhindi
(Hibiscus esculentus), Hollyhock (Althea rosea), Silk cotton tree (Eriodendron anfinictuosum) , Mulberry
(Bombax malabaricum), John bull tree (Thespes!a populnea),
Deccan hemp (Hibiscus cannabinus), Musk melon
(Hibiscus abelmoschus), Indian mellox^r (Abutilon spp.).
Shoe flower (Hibiscus rosa-sinensis), Cape gooseberry
(Physalus peruviana) , Wild tobacco (Solanum verbascifoliurn) ,
Sambhal (Solamalia malabaricum)^ Bajra (Pennisetum typhoideum),
Wheat (Triticum vulp:are) and Maize (Zea mays).
Both the nymphs and the adults suck the juice from the bolls and the punctures made by them open way for secondary infection by micro-organisms. The salivary secretion of the bugs has a harmful effect on the developing seeds which either degenerate or stop growing. The fibres are stained yellow and this results in considerable economic loss to cotton growers. Dysdercus cingulatus has also been observed to introduce the fibre staining bacterium,
Nematospora 'gossypii into the bolls (Narayanan, 1962). - 10 -
^Part I - ECOLOGY
OVIPOSITION
General.
Members of the family Pyrrhocoridae deposit their eggs in loose soil or under debris lying in the field.
Ballard and Evans (1928) observed that D. sidae oviposited in soil at a depth of one inch below the surface or under some such protection as a piece of wood or a box lying on the ground. D. nigrofasciatus deposits its eggs close to the base of a plant or in exposed heaps of cotton seeds
(Hargreave and Taylor, 1937) while D. cingulatus oviposits in cracks in soft soil (Mehta, 1930). The female protrudes the posterior part of the abdomen and thrusts it into the soil. The head remains elevated above the ground and a cluster of eggs containing 100 to 130 eggs is deposited at one place in about 2 to 3 hours (Srivastava and Bahadur, 1958)
During the present studies the females of D. cingulatus usually deposited their eggs in small crevices between cotton seeds or at th? bottom of petri dishes in which the seeds were kept. The eggs were laid singly at intervals of 40 to
60 seconds and were later arranged into batches with the help of hind legs. The whole process lasted for one and a half to two hours. - 6 -
Effects of environmental conditions on ovlposltlon.
Temperature and humidity greatly affect oviposition.
Husain (1927) observed that a moist surface was necessary
to induce oviposition in D. clngulatus and atmospheric
humidity was of no importance but Mehta (1930) obtained
eggs of this species even on dry soil when there was enough
moisture in the atmosphere. The females readily oviposited
under laboratory conditions at 32.2°C and 70 to 100 per cent
humidity but no eggs were laid at temperatures below 20®C.
Extremes of temperature impaired the rate of oviposition
in p. koeni^ii and the number of eggs laid at 15 and 35°G
was much less than at 20 and 30°C (Bhatia and Kaul, 1966).
As compared to 90 per cent of the females of D. fasciatus
that oviposited at 280C, only 30 per cent laid eggs at
20°C (Clarke and Sardesai, 1959).
Little or no precise data exists concerning the
duration of the preoviposition and oviposition periods in
cotton bugs. Ullyett (1930) found that the preoviposition
period of D. nigrofasciatus varied from 7 to 16 days. The
eggs of p. cingulatus were laid 3 to 6 days after copulation
at 35^0 while at temperatures varying between 21.1 and 30°C
they were deposited after 13 to 20 days of the copulation
(Mehta, 1930). The. oviposition period in the case of i* koenigii was found by Bhatia and Kaul (1966) to be
22.2, 10.2 and 10.4 days at 20, 25 and 30°C respectively. - 13
The present author kept newly emerged adults of
clngulatus at 29°C and 60 to 70 per cent humidity in glass tubes measuring 15 x 2.5 cms. in size. A single pair was kept in each tube containing moist cotton seeds.
Observations were recorded daily and the eggs obtained
Mere removed vrith the help of a brush. The number of eggs laid per female per day during the oviposition period was determined. The daily average varied from 13.6 to 48.7 in the first five days during which time more than 75 per cent of the total eggs had been laid. Oviposition declined rapidly thereafter (Figure 1). There were no deaths during the first five days of the oviposition period.
That the rate of oviposition varies under different environmental conditions was studied by keeping individual pairs of freshly emerged adults in glass vials in temperature controlled cabinets. The vials were tied to the neck of glass jars measuring 20 x 10 x 5 cms. in size and containing salt solutions for maintaining the desired humidity.
3 pairs were kept at each combination of temperature and humidity. The humidity percentages maintained and the salts used in each case were as belows-
Temperature Humidity Salt (C.P) ^
16 45.4 Chromium trioxide
15 76.0 Sodium chloride - 10 -
Temperature Humidit% y Salt (C.P) oc
20 . 66.O^' Sodium nitrite 20 81.0 \ jimiaonium sulphate 20 90.0 1 Zinc sulphate
30 63.0 Sodium nitrite
30 81.1 Ammonium sulphate
30 • 92.9 Ammonium dihydrogen phosphate
40 66.8^'' Potassium iodide
40 74.7 Potassium chloride
40 79.5 Potassium bromide
The average mamber of eggs deposited per female decreased with a rise in temperature and fall in humidity
(Table 1). Irrespective of humidity conditions the females died within 24 hours of emergence at 40°C without laying any eggs. At 16°C also no eggs were laid inspite of the females living for 16 to 36 days. These_observations are in conformity with the earlier findings of Mehta (1930) who did not observe any oviposition in p. cingulatus at
40®G but differ from those of Bhatia and Kaul (1966) who did find D. koenigii ovipositing at 15°G though the eggs laid at this temperature were fewer in number than those deposited at higher temperatures. - 10 -
50
45 o o 40 bl in y. 35 O QC 30 UJ UJ o cfi 25 Z ^ < Z 20 H UJ O 15 O< OS 10 UJ 5
6 7 8 9 10 M 12 13 14 15 16 17 18 19 20 DAYS AFTER EMERGENCE
Figure 1. Average rate of oviposition and number of deaths of 11 females at 29^0 and 60-70 per cent humidity. - 1 0 -
o o 0 3 C O 0 5 O o o« m # « H o s • • © o o C O 0 3 C O 0 3 o o o S c C - f Hp m ! > < o o U 3 C O 0 0 0 3 Oi O o o t u o W « • o - o C D l O H • • • fi t s C o o H 0 3 H H r H 0 3 O o o o ® • H • P • H 0 W © M o o ' C O J ,C O o C O o 1 O o a <3> n J • • • « I f • • • • • • • H f H o o i 0 3 l O o o o o > ® i H 1 C O C O 0 3 o 0 3 1 0 3 0 3 0 3 c 1 0
• H xs • H s 4 - 9 1 • r H T ? O ft a o o o o o O o O O o o • H ffl • • • • • • • • • • • > O o o o o o o o o o o o
O® C h • H o o o; H 0 0 U 5 « H • • | H | L O d O n; H 0 3 iOj ( 3 5 i > C D C O O) y s f CX 3 O i
0 ) H E H
u A B A A n J O U D U 3 o o o o o o o o ® O 1 - 1 0 3 0 3 W c o l C O £ 0 ft a® E H - 10 -
60 55 50 45 V 40 IaJ cr 35
1- 30 < 220e0 2463 Qt UJ zs I Q. { zo z ?7S3 232.3 UJ • \ H 15 K) 5 I I J L J L J_l 40 45 50 55 60 65 70 75 80 85 90 95100 ^ HUMIDITY
e u
ecJoj/raf H Figure 2. Average number of eggs laid in controlled environments. - 10 -
m M-o i m T} fH 03 « (M 03 03 CO O 0) I •H p- ® i^H ® a •P P o H H
+s to o •H >5 •rH m «s -P o TH m > o ffl p 0 W) •H 1 rt t£> CO CO O > +3 • • • • • • m H 03 H H H 03 ? {A -P CO o •n p •H ts CO OS O O- C£5 OJ pi o H CO X! •H i s»u ® -C! p0). f-i o cd X U3 (X) •H fl'm w H -P (P O !>, •H fn •H cd CO PJ O P •Hv 0 P to m O O VD CO o O 0 • • • • > ffi a CD CO lO U3 00 o P •H 0) H H H e > rs Q> O PJ P o •H P o H 00 O o ^ ai CT)' ai ^ H H H H m to 1 o a O) ffl P o p. ^ •H i> •P d X 00 r- ^ (i) o a o- H H H (!) ri •H m f-4' •H P •H cd m qj O o o 0) •r->l M o o O O CO ri flj • • • • • • o a o fn 05 00 00 00 l> •H <]> 0) © H H H •P flj EGGS General features. The oval white eggs of D. clngulatus when freshly laid measure 1.119 mm. x 0.346 ram. in size (Figure 3). The colour changes from white to yellow and finally becomes orange in 32 to 36 hours. Effect, of temperature and humidity on thg^ hatching of the eggs. The eggs of D. cingulatus hatched in 6 days at 36®C and 82 to 100 per cent humidity but failed to hatch when the humidity was below 82 per cent. At 33°G and a humidity of 79 per cent or more the eggs hatched in 6 to 6 days but no hatching could be observed when the humidity was below 79 per cent (Mehta, 1930). Clarke and Sardesai (1959) found that the hatching of the eggs of D. fasciatus was also affected by temperature conditions. The eggs did not hatch at temperatures below 25 and above 30°G. 94 per cent of the eggs of D. superstitiosus hatched at 30°c and 72 per cent humidity in 4.05 days. The rate of hatching, however, became lOO per cent when humidity was raised to 9^ per cent keeping the temperature constant at 30°C. The duration of incubation period also decreased from 4.05 to 4.0 days (Vrydagh, 1941). The present author .^draee^d" freshly laid eggs of P' cingulatus >ir desired temperature and humidity en^w^s^iHsen-ts. - 10 - ESG FIRST INSTAR rirrn instai TMWO WBTW. "Figure 3. The egg and I to V instar nymphs of Dysderc-us c^gulatus. - 10 - Th^^were examined at twenty four hour intervals to determine the number of nymphs hatching. Temperature had a pronounced effect on the' duration of the egg. stage and the eggs kept at 16 and 40°G failed to hatch regardless of humidity conditions. In general the incubation period decreased with an increase in temperature (Table 3). The percentage humidity however influenced the rate of hatching of the eggs and the hatch rate was lower at humidities belox-J 60 per cent than at higher humidities. The threshold temperature for the development of eggs as established by figure 4 lies at 10.5®C. The values of K at 20"C = 106.356 26°C = 103.82 30® G ^.103.36^ The values of^^aCthe three temperatures are almost Identical, which suggests that the theoretical threshold of development as determined is approximately correct. Extension of Incubation period by refrigeration. Stewart and Walton (1966) found that the time required for the hatching of the eggs of the Southwestern cornborer, / Zladiatrea grandiosella when refrigerated at 7.2 to 12.7°C for different periods of time and then allowed to hatch at room temperature was in direct proportion to the age of eggs, the refrigeration temperature and the duration of - 10 - UJ Z CL O S£J > UJ O 10 IS 20 25 30 TEMPERATURE^C Figure 4. Effect of temperature on the development of Dysdercus clngulatus eggs. - 18 refrigeration. As no data exists on the effects of suboptimal temperatures on the hatching of the eggs of P* cingulatus ^ an attempt was made to study the phenomenon in this speciesi Eggs of different age groups were kept in a refrigerator for 24, 48, 72, 96 and 120 hours. The temperature of the refrigerator was fixed at 10°C and the humidity varied from 44 to 47 per cent. It was found that while 42.0jg, 28.0^ and 4.0^ of the freshly laid eggs hatched after 24, 48 and 72 hours of refrigeration respectively, none of them hatched when refrigerated for 96 and 120 hours (Table 4), Of the 24 hour old eggs 48.0^ and 46.0^ hatched after 24 and 48 hours of refrigeration but no hatching was observed when they were refrigerated for 72, 96 and 120 hours. The hatching of the 72 hour old eggs was not inhibited even by the longest refrigeration period of 120 hours and similar was the case with 96 and 120 hour old eggs. In the control held at room temperature the percentage hatch was 84.0. These observations suggest that the eggs in advanced stages of development are not so adversely affected by lower temperatures as the ones in early stages of development. The duration-of the incubation period was found to be I directly proportional to the refrigeration time. In the case of freshly laid eggs it was 6 days when the eggs were - 10 - refrigerated for 24 hours arid 7 days when the refrigeration period was ext-ended to 72 honvs* Similarly the 72 hour old eggs hatched in 6 days when refrigerated for 24 hours ! hut took 10 days to hatch when refrigeration period was prolonged to 120 hours. - 10 - Table 3 . Effect of temperature and humidity on the hatching of the eggs Temperat"ure Humidity % Incubation o„ hatch period in days 16 46.4 0.0 0.0 16 76.o' 0.0 0.0 20 20.0 44.0 10.0 20 66.0 72.0 11.3 20 81.0 84.0 11.09 20 90.0 66.0 11,0 25 67.7 42.0 7.09 26 81.1 86.0 7.16 26 93.0 60.0 6.3 30 26.6 64.0 4.0 30 36.4 60.0 4.1 30 81.1 86.0 6.3 30 92.9 66.0 6.78 40 42.4 0.0 0.0 40 66.8 0.0 0.0 40 74.7 0.0 0.0 40 79.6 0.0 0.0 o rt •P - 10 - cd»i3 w Vi P O •H £d O O O O C5> 0> 0) O PM 00 03 t£> XI o o o o o to • • § a (d o o o o 00 o o (d o H NYI^IPHS , Rearing. The nymphs of cotton stainers can be easily reared under the laboratory conditions. Gearing (1956) used shallow tin cylinders having the roofs and floors covered by cotton cloth for the large scale breeding of cotton stainers in Uganda while Clarke and Sardesai (1969) kept the nymphs of fasciatus in perforated zinc boxes suspended in the middle of the cag^S/ at a temperature of 28 + 1°G and 70+6 per cent humidity. They were fed on cotton seeds. Water was supplied in plastic tubes, each tube having a small hole plugged with a small wick that projected slightly from the surface so that the insects could take water from it. Reddy and Naidu (1967) used glass troughs measuring 6" X 10" for the rearing of D. cingulatus while Bhatia and Kaul (1966) reared the nymphs of D. koenigii on soaked cotton seeds in glass jars, 4" x 2" in size; and containing moist sand at the base. JDuring- the present studies freshly emerged nymphs were kept individually in celluloid tubes, 8x3 cms. in size and containing' moist cotton seeds which were changed daily. Of the 49 nymphs reared at 26.7^0 and 60 to 70 per cent humidity, 24 developed into adults while only 18, 18, 14 and 16 adults could be obtained from the 30, 30, 30 and 27 nymphs kept at 30.3, - 10 - and and 60 to 70 per cent humidity (Table 6). The nymphs developed faster at higher temperatures and completed the development in 15.79 days at 33.1®c in contrast to a nymphal duration of 27.18 days at 26.7°G. Very few nymphs died in the first instar and the highest mortality of 66.6 per cent was observed among the third instar nymphs (Table 6). Mumber and duration of nymphal instars. Freshly hatched nymphs -were also kept in glass vials f in the desired envJ^onments-of^ temperature and humidity. They were fed on moist cotton seeds which were changed at 24-hour intervals. The nysjphs developed slowly with a high percentage of survival at 20°G and 66 per cent humidity but the development was much faster at 30®G and 63 per cent humidity (Table 7). The zones of temperature and moisture conditions suitable for development of nymphs are i&^VTo^ImiieljS^ demarcated in figure 6. The nymphs, however, failed t© develop at humidities of 90 per cent or above irrespective of the temperature conditions. They died in 4 to 5 days at 20°G and 90 per cent humidity and 2 t© 6 days at SO^c and 92.© per cent humidity. This is in conformity with the earlier findings of Mehta (1930) and Bhatia and Kaul (1966) who observed that the young nymphs of D. cln^ulatias were highly sensitive to high temperatures and humidities and temperatures of 15 and 40®C were unsuitable for the develop- ment ©f D. koenipil. - 24: - 50 45 40 35 J»30 s» 111 A. S 20 IS 10 J L -I U 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 ^HUMIDITY Figure Nymphal duration in days in controlled \ environments. Zone I represents favourable combinations of temperature and humidity _ while zone II indicates unsuitable condition^, - 10 - W 01 • a> H OS o 00 • ta 1! I O CO CO c3 03 lO cd (S) H ^ oa d) CO A (C a® s^ 0) +3 A a Vl nH O^ O (1) (D Cd bfi bO (1> ^ «3 43 (35 la o 01 • pj M 00 0)43 -P 8 10 O ftH a fs ffi w 0 cd O) u u $ as CS m CO o 00 o a> 5> +9 © ft o O a H H H ^ H 0) P. 05 -P +3 C6 00 ! a > +3 O o CO © H m # Q) o H CO Si (p i H •p •H -ES § •p 01 Ei 0) 0 CO CO 00 (0 CO <1» o I +3 • iO ft I m CO CO a> H 03 • • td 0> * 03 03 O fH o CO • CO CO • CO • 0) o 00 o 1 o 1 I o I H ^ 01 • CSi CO o Gi CO O CO 1 ^ • —* • • w • V-X (D a> oj O) CO O) H 03 CO 03 I - 27 - +> <»-( Q) O H Pi+9 f%4 "H +9 +» +3 •p O (Si & Pi •H U3 H > +> to 00 m • 1 1 1 1 U cd TO 03 H M 4J> TO IN IN M m 00 C3i ^ LO 03 to M 03 03 M m O TO TO td •P O o M W O 03 w .H o O © o O H 0> 03 IN 03 • • • • • • • • • to H o W H oa CJ> IN •"If IN 00 05 to 00 OJ IN 0) ^ cd EH 2 o lO to o o o o o o © o H H 8 TO TO TO ^ - 10 - The existence of five nymphal instars was checked by the formula of Dyar (1890) which utilizes the ratio of increase in the width of head capsule in successive instars and is used as a factor for determining the number of instars in the life cycle of an insect. Width of head capsule in mm. Instar Observed Calculated I 0.517 0.489 II 0.686 0.66 III 0.861 0.89 IV 1.21 1.20 V 1.63 1.63 The calculated widths do not depart much from the measured ones suggesting thereby that no ecdysis was overlooked, Description of various instars. The nymphs pass through five instars (Figure 3). The first instar nymphs are oval in shape, light yellow in colour and measure 2.074 mm. in length. The colour becomes reddish within 24 hours of hatching. There is no clear distinction between the thorax and the a.bdomen. Antennae are red in colour and four jointed, measuring 1.064 mm. in length. The terminal joint is swollen and - 10 - longest, measuring 0.618 mm. In length. There are two tarsi in each leg. The proboscis is short and four jointed measuring 0.914 mm. and reaches upto the first abdominal segment when at rest. Three small openings of the stink glands are present on the 3/4, 4/6 and 6/6 abdominal segments and a red spot is present near the third opening. The second instar nymphs are deep red in colour and measure^2.66 mm. in length, jjntennae ar© four jointed and 2.46 mm. in length. A four jointed proboscis measuring 1.62 mm. in leogth extends practically upto the end of abdomen. The median, black orifices of the stink glands are visible on the 3/4, 4/6 and 6/6 th inter-tergal membranes of the abdomen which are retained throughout the njrmphal life. The nymphs belonging to the third instar are 4.6 mm. long. The antennae measure 3.68 mm. in length and the proboscis is short, 2.64 mm, long and extends upto the third abdominal segment. The most characteristic feature of this instar is the appearance of the mesothoracic wing pads which are 0.299 mm. in length. They are ©range in colour in the beginning but become black afterwards. Later on the metathoracic wing pads also develop. Three pairs of faint white dorsal spots appear, one pair each on the 3rd, 4th and 6th tergal plates. Three faint white bands also develop on the 2nd, Srd and 4th sternal plates. - 10 - The fourth instar nymph measures 6.95 mm. in length. The antennae are 6.52 mm. l©ng. The proboscis measures 4.14 mm. and extends upto the second abdominal segment. The wing pads are black in colour and are 0.513 mm. long. The ventral side of the abdomen has four transverse \?hite bands on 2nd, 3rd, 4th and 5th sternal plates. The dorsal white spots are also visible on 3rd, 4th and 5th tergal plates. The fifth instar nymphs are 9.06 mm. long and characterized by the presence of long wing pads, measuring 1/47 ®ra« in length. The paired white spots are found on 3rd, 4th and 6th tergal plates. The complete white transverse bands are found from 2nd to 6th sterna while the band of the 1st sternum is incomplete. The proboscis measuring 5.57 mm, in length, extends upto second abdominal segment. This is the final instar of D. cingulatus. The different instars can be easily identified with the help of the following key. 1. Proboscis extending upto 1st abdominal segment - 1st instar Proboscis long, extending beyond the first abdominal segment 2 2. Proboscis extending upto the tip of the abdomen or at least upto the fifth segment - 2nd instar Proboscis not extending upto the fifth segment. Mesothoracic wing pads conspicuous, metathoracic pads appearir^ later on 3 - 10 - 3, Proboscis extending upto third abdominal segment* 3rd, 4th and 6th tei^a with faint spots. 2nd, 3rd and 4th sterna with faint bands - 3rd instar Proboscis extending upto second abdominal segment. Bands and spots on tei^a and sterna distinct. First abdominal sterna with incomplete band 4 4. White spots on 3rd, 4th and Sth terga and white bands on 2nd, Srd, 4th, and later, on the 5th sternal plates - 4th instar White spots on Srd, 4th, Sth and some times on 6th abdominal terga, bands on 2nd to 6th sterna complete Sth instar - 10 - ADULTS Seasonal abundance. The adults feed on a variety of plants. They are especially destructive to cotton and suck the juice of green bolls, attack seeds and make the lint dirty with their yellow exereta. Daring the present studies the seasonal abundance of D. cingulatus was studied by making weekly collections of fifteen minutes each from three host plants, Gossypium hirsutum; Althea rosea and Hlbiscus esculentus over a period of three years (Figure 6). hirsutum was probably the preferred'host plant, the maximum catch from G. hirsutum, A. rosea and H. esculentus being 133, 56 and 49 bugs respectively. Depending on the availability of the host plants the bugs were common on Gossypium Mrsutum from September to December, remained hidden under fallen leaves and other debris during January and February and then thrived on A. rosea from March to May till the plants withered away or hot and dry season prevailed. H. esculentus was infested from July to September or October when Gossypium become available for attack. No significant difference could be observed in the sex ratio, the percentage of males and females collected from different plants being as follows. 33 - • S B CO H to pi fn bC •H fl •H O • tn el ps t3 o fi! p^ CD m cn & -p o ch H O O 0) m O 0) s . B eC Ki ® m d O a fH C o • cd 0) fH bD •H [X4 O rf^ O O rf^ in ^ 9 Kt to N i2 3 S133SNI JO tl39MnN 1/ - 10 - 1964 1965 1966 1967 Host plants Male Female Male Female Male Female Male Female Gossypium hirsutum 50.34 49.65 52.07 47.92 46.79 53.2 - Hibiscus esculentus 57.84 42.15 50.83 49.16 45.4 54.58 - £Lthea rosea 52.06 47.93 50.0 50.0 56.62 43.37 Copulation. The bugs copulate freely under caged conditions. The male covers the female, twists its abdomen and brings the posterior part of its body close to the abdomen of the female. The aedeagus is protruded, inserted into the vagina of the female and the pairing adults turn their heads in opposite directions. They continue to feed and the female drags the male along. Mac Gill (1935) found that pairing in D. howardi takes place in about 2.8 days after the emergence of the females. In the case of D. cingulatus the precopulation period varied from 3 to 7 days at 30 to 37^*^ but was prolonged to 15 days when the temperature varied from 25 to 30.6°G Mehta (1930). The present author observed that the precopulation period decreased with an increase in temperature and fall in humidity (Table 8). - 35 Table 8. Effect of temperature and humidity on copulation Frecopulation period in days Temperature Ifemidity Oq % Minimum Maximum Average 15 45.4 0,0 0.0 0.0 16 76.0 0.0 0.0 0.0 2© 66.0 8.0 9.0 8.3 20 81.0 10.0 11.0 10.3 20 90.0 9.0 12.0 10.3 30 63.0 2.0 3.0 2.6 30 81.1 2.0 3.0 2.6 30 92.9 3.0 4.0 3.3 40 66.8 0.0 0.0 0.0 40 74.7 0.0 0.0 0.0 40 79.5 0.0 0.0 0.0 - 10 - Irrespective of the humidities the bugs failed to copulate at 15°C and 40°C. Of the 30 pairs observed at 29 + 1°C " 17 copulated after 3 to 5 days of emergence. The remaining 13 pairs survived forgnly 1 to 3 days. and-dljd_no.t~-copulrate- The time taken for copulation varied from 14.6 to hours at 29 + 1°C as against 3 to 5 days observed by Mehta (1930) at temperatures fluctuating between 18.3 to 21.1°C. Longevity. Pomeroy and Golding (1923) have recorded a maximum longevity of 57 days for males and 47 days for females of D. superstitiosus. The duration of adult life in D. fasclatus, S* nigrofasciatus and D. superstitiosus was found to be 65, 71 and 91 days for males and 62, 72 and 43 days for females by Hargreave and Taylor, (1937). Barbosa (1950) observed that the males and females of D. nigrofasciatus lived for 48.8 and 33.7 days at 25°C and 100 per cent humidity. During the present studies the males of D. cingulatus lived for 4 to 38 days at a temperature of 29 + l°c. The females survived for 4 to 28 days. This is a much shorter duration than that observed by Pomeroy and Golding (1923) in the case of D. superstitiosus or by Hargreave and Taylor (1937) in fasciatus, D. nigrofasciatus and D. superstitiosus and may due either to environmental factors or certain inherent differences among the species. That temperature and humidity have a profound effect on the longevity of D. cingulatus has been shown by Mehta (1930) - 10 - who found that the adults of D. cingulatus lived longest at 12.7°C to 26.1°c and 66,0% humidity. This longevity of 93 days was reduced to 2 to 4 days at 17.0^ humidity and 38.3 to 40.8°C and the hugs did not survive for more than a few hours at 41.1°C to 41.70c and 37.0 to 100.0^ humidity. The average longevity of the adults decreased from a low to a high humidity at 16°C (Figure 7.). At 20 and 30°C, however, a decreased longevity was observed from a low t© an intermediate- humidity hut then it increased with subsequent increase in humidity. The longevity also decreased with a rise in temperature and the males lived longer than the females. The maximum longevity was 42 days at 20°c and 66.0 to 90.0^ humidities. The females lived for 16 to 35 days at 15°C and 46.4 to 76.0% humidity but failed to lay any eggs. Theyhowever, died within 24 hours of emergence at 40°C irrespective of humidity conditions. This is in agreement with the findings of Ifehta (1930) who found the bugs de^within a few hours at 41.1°C to 41.7°C and 37.0 t© 100.0% humidity. The zones of suitability for longevity of adults to temperatures and humidities are approximately delimited in figure 7.. A comparison of figures 2-andJ7.^show.S- a Jteneral agreement of temperature and humidity relations for reproduction and longevity. With a change in temperature from 20 to 30°c there was a greater reduction in the longevity of adults than in oviposition, suggesting thereby that higher temperature has a more adverse effect on the longevity of . adults as compared to oviposition. - 10 - 100 r 95 2^0 420 X 90 I8X) 85 17.0 K 80 I4LI 00 * K t II 0.0 111 OD G 70 2IJ0 Y X |6S /0 0 17.5 ^ 60 37.3 55 50 35D X 45 258 J L J L J_J 5 10 15 20 25 30 35 40 45 50 temperature'^c Figure 7. Longevity of adults in days in controlled environments. Above i maximum longevity. Belox^r s average longevity. - 10 - Selection of admits, for extended survival ^thont food and water* The effects of scarcity of food and water on the longevity and fectmdity of D. cingnlatns were studied hy starving newly emerged adults at 29 + 1®C and 60 to 70^ ^^huffiidity for 48, 72, 96, 120 and 144 hours in glass jars measuring 16 x 2.5 cms. in size. All the adults survived a starvation period of 48 hours but the mortality was 100 when they were starved for 140 hours. The 16% adults that survived a starvation period of 120 hours were fed on moist cotton seeds and reared to produce the next generation which was similarly starved. In this way selection was continued ifor five generations. H^cuwur^ rf The results Obtained (Tahle 9) show that starvation resulted in an increased "biotic potential but reduced longevity of the adults. The number of eggs laid per female increased from 82.6 to 194.6 in five generations of starvation as against the longevity which decreased from 23 and 24 days to 20.4 and 21.9 days in males and females respectively. That resistance to starvation increased during selection is clear from figure 8. While 85^ of the parents died after 120 hours of starvation, all of them survived this period of starvation after five generations of selection. The females were more tolerant to starvation and lived longer than the males. ^ - 10 - Table 9 • Fecundity aM longevity of D, clngulat'a.s when starved for 120 hours " " Generation No, of eggs laid Longevity in days per female Male Female P 82.5 23.0 24.0 F1 147.5 14.0 15.5 F2 128.6 14.0 23.1 F3 161.6 12.7 13.2 F4 162.0 13.8 14.1 F5 194.5 20.4 21.9 - 10 - cn ae nS rt O rHl PJ •H U oe O W (A «H g (0 JP Ul oe +3 0) ff Q. •H 'O rH Mo J? «0 u >cC u O IC -UIl oJ Ul -P Q) a. (A 0) iJ? o PH CO i5 f-l 0 f0CHO) -r J0) J? MI •C tv 00 iC / Q) CL U I I I—u ^M P>4 AXnVlHOW lN33|Od - 10 - EFFECTS OF DIFFERENT WLMT FOODS ON FECUNDITY, FERTILITY MD DEVELOPMENT The insect pests of a seasonal crop tend to spread to other hosts in order to obtain a regular supply of food througho\at the year and t© ensure their survival during the the absence ofXmain host, Watson (1916) observed that D. delauneyi infested the pods ©f Eriodendron anfractuosum and ThesPesia populneg in the absence of cotton crop and it has been reported (Results of cotton cultivation experiments in Forra^a, 1936) that D. cingulatus causes considerable damage to Mbiscus. sugarcane, mango and other plants when cotton plants are not available. Recent reports from several parts of India indicate that D. cip^ulatus which prefers cotton plants can survive on a number of plants including Triticum vulgare, may^, Pennisetum typhoideum, Hibiscus cannabinus, BH.biscus abelmoschusj Hibiscus rosa-sinensis, Althea rosea. Riysalup peruviana and Solanum malabaricum (Sohi, 1964). It seems, therefore, desirable to find out if there exist any biological differences whsn the species is reared on f DUo^c: different food plants as has been reported by Geering and Coalcer (1960) in the case of p. superstitiosus. Four types of food materials, SLbiscus esculentus^ Pennisetum typhoides^ fiorghum vulgare and Gossypium hirsutum were fed to groups of newly hatched nymphs reared individually in glass vials. 100 nymphs were reared on each type of food - 10 - ^material except in the case of P. typholdes-where-Qnlv 90-n7mph"s~wef^bred. The food smpplied was presoaked in water-exce^t'' the H. esculentus ^rfjietor was made available as green pods. Fresh food was provided after every 24 homrs. The admits obtained from each gtoup were allowed to feed on the same type/'of food on which they had been reared as nymphs and abservations were recorded on their fecundity, fertilityand longevity. The development mpto the third instar was almost similar on all types of food and it was only in the fourth and fifth instars that the development period varied. The. nymphal duration was shorter in the case of nymphs reared on cotton seeds than those reared on H. esculentus, typhoides or S. valgare. It was slowest on vulgare (Table 10). Geering and Coaker (1960) also found argreater^ nymphal duration when the njrmphs of D. superstitiosus were X reared on Sorghum grains as compared to those fed on cotton seeds. The percentage mortality of the nymphs was lowest -T^hen-reared on cotton seeds and of them developed into adults as compared to 50.0Jg, 61.15^ and 48.0Jg that completed nymphal development on H. esculentus^ typhoides and S. vulgare respectively. The mortality in different instars was inconsistent and did not appear to have been effected by the nature of the food supplied. The adults readily fed on all the food materials and no significant variation could be observed in the precopulation period. 30.OJ^, 16.and 22.3J& of the females bred ©n H. esculentujs, F. typhoides and - 10 - "^l^ave did not lay any eggs whereas all the females reared on G. hlrsntum oviposited. The highest number of 106.4 eggs per female was obtained when they were fed on H* esculentas. The rate of egg hatch also varied, being 76.4^, 70.8^, 50.1^ end 60^7% in females fsd on H. ese-glentias^ S* hirsutum, P. typhoides and S. vulgare respectively. The longevity of the adults was also affected by the kind of food supplied and those fed on G. hirsutum lived longest (Table 11). Though no biochemical analysis of the contents of food materials supplied was made, it appears that Hibiscus esculentas and Gossvpium hirsutum are the preferred food materials of D. cingulatus. The average number of eggs laid per female was 106.4 and 100.2 on H. esculentus and G. hirsutum as compared to 76.©9 and 29.0 eggs laid by a single female when fed on F. typhoides and S. valpare respectively and similarly the adults lived longer when fed on hirsutum and H. esculentus. - 10 - ta XI 1=1 Rf to (M H o yj IP!s O • • in 1-1 (O 00 CO U3 •p •p w 03 CO to 0 cd OT •P ^^ H§ Pk •H 0$ m +3 fH M •p 1 & § m CO lO• 00• ©• Es•. 03 u • • • • Q} C^OQ Cv CO o •p O 0•) H CO •H CO a 05 lO U3 C3 >13 ® H 0) to bO o tuO H W © (d •P o ©H -d m •p to a S ® a pj 3 to B a ® a t to B gto ® w a H •H •p to to •H p to to u O o to ® o t§ o :d ® 04 CQ - 10 - Part II - CONTROL REVIEW OF LITERATURE As early as 1914, Lambom recommended that the nymphs ©f cotton stainers could fee easily collected by small nets and destroyed by dipping in wide momthed tins containing water and kerosene oil. Cowland and Rattledge (1927) suggested the destruction of the colonies of D. superstitiosus and p. nlgrofasciatus on tebeldis as the best method for their control. Terpineol and Trimethylamine were found to be useful repellants for D. sidae and split kernels when combined with poisoned water in a trap served as an effective bait for the nymphs of p. sidae in Queensland (Ballard and Evans, 1928). Campos (1929) obtained good control of D. concinnus with nicotine sprays and the cube "Lonchocarpus nicon" has been successfully employed against D. ruficollls by Wille, 1937 A cube containing rotenone killed 20^ of the adults in 24 hours under laboratory conditions. The remaining of the adults were -paralysed and of these died within the next four days. Dusts containing 2»5% nicotine or 1 part of pyrethrum and 2 parts of talc ®r kaolin have been successfully used as a repellant for D. sidae. A spray ©f pyrethrum and soap has also been found effective against this species (Insect pests and their control, Ag. Gaz. N.S.W. 1940). - 10 - Powdered seeds of Mammea americana and a mixture of such seeds and pods of Pachyrhizus erosus caused 19 and 32% X' mortality of D. andreae (Report of the Federal experiment stations in Puerto Rico, 1945). Mathur, ^ al. (1961) observed 40 and 87^ mortality of the adults and nymphs of D* cingulajbus when half an hour of being treated with pyrethrum marc, containing 0»2% pyrethrins. The mortality became 80 to 100^ after 48 hours of the treatments. DDT proved ineffective against D. ruficollis but BHG dusts gave satisfactory control of the pest for at least ten days and was slightly more effective than sabadilla dust (Wille, 1946). Later in 1966 the same author succeeded in controlling D. peruvianus with BHG dusts in tPeru. Trehan, et al. \ (1961) tested a number of insecticides against the fifth instar nymphs of D. cingulatus and found BHG to be the most effective insecticide; the order of toxicity being BHG, endrin, parathion, aldrin, DDT, dieldrin, lethane, toxaphene and rhothane. While BHG, endrin and parathion were respectively 4, 2 and 1.5 times as effective as DDT, lethane, toxaphene and rhothane were only 0.23, 0.22 and 0.07 times as toxic as DDT. Aldrin and dieldrin were almost as effective as DDT. Simon, et aJL. (1960) found sevin to be a better insecticide than parathion for the control of D. peruvianus because of its residual effectiveness which lasted for 4 to 10 days and lower toxicity to man. - 10 - Salkeld and Potter (1963) conducted experiments to find out the effects of age and stage of development of the eggs of D. fasciatus on their resistance to insecticides. Three insecticides, DNOG, allethrin and HETP were used and the results obtained showed that resistance increased with the age of the eggs when triethanolamine salt of 3 s 5 dinitro-ortho-cresol was used. Similarly the resistance to allethrin increased rapidly with the age of the eggs while resistance to HETP decreased with the age of the eggs. Banerjee and Basu (1955) used tetrax as a systemic insecticide for the control of D. cingulatus and found it to be highly effective when introduced through the root system of the plants. Lall and Tiwary (1958) studied the systemic action of three organic phosphates, systox, pestox and diazinon against D. cingulatus and found that systox was the most promising of the three chemicals. None of the phosphates produced any injury to the plants. In fact more fruits were produced by the treated plants than the untreated ones. I Reddy and Naidu (1967) studied the toxicity of sevin, malathion and endrin by applying topically O.OOOl ml. of the insecticides on different parts of the body of D. clngulatus. The head was found to be the most sensitive site followed by wing base. Pronotum and the third abdominal sternum were comparatively less sensitive than wing base and the abdominal - 10 - tergum was the least sensitive of all the parts treated. Garcia (1969) reported that D. permvlanug can heeome resistant to BHC when pmt to insecticide pressure under laboratory conditions. In 11 generations of selection the species became 4S times as resistant as the normal strain. The sterile male release teclinique, proposed by Knipling (1937) and later utilized with commendable success in 1966 by Baumhover and his associates for the complete eradication of screwworm, Callitroga hominivorax from Curacao island, opened a new field of research in the control of insects. The very idea of eliminating insect population through sterilization changed the line of thinking and a large number of chemicals have been discovered which could induce sterility in insects without causing any apparent damage to their bodies or hindering with mating capabilities. La Brecque, ^ si. (1960) have demonstrated the chemosterilant activity of several compounds for the control of houseflies. A significant reduction in the hatch rate of eggs was obtained in Mthonomus grandis when the females were allowed to mate with males sterilized by feeding them on diet containing 0.0001 to 0,Q2% of apholate or on plants sprayed with 0.6 and 2*5% solutions of apholate (Hedin, et 1964). Sterility has been induced in the males ©f cucumber beetle, Diabrotica balteata by feeding them on diet treated with apholate, tepa or metepa (Creighton, ^ al., 1966) and Ladd (196©) observed that topical applications of apholate, - 10 - tepa and metepa produced appreciable sterility in the adults of the Japanese beetle, Popillio .laponiea. Mistafa and Naidu (1964) found apholate to be an effective chemosterilant of D. cingulatus. The males when exposed to 0.7 mg./sq. inch apholate residues for 4 hours were found to be completely sterilized and no hatching was observed when such males were allowed to mate with the normal females. The females were less susceptible to the sterilizing effects of apholate than the males and had to be exposed for 18 hours to obtain 100^ sterility. The sterility produced by the chemosterilants may be permanent and the treated individuals may not regain their normal fertility. Dame and Ford (1964) foomd that the males of Aedes aegypti when exposed to tepa residues, retained their sterility even in their fourth mating with the females. La Brecque (1961) also reported non-reversible sterility in houseflies when fed on sugar treated with tepa or apholate for first five days after emergence. Mating vigour and sexual competitiveness of the chemosterilized males has been studied by a number of workers- Davis, et al. (1959) observed a significant deficiency in the mating vigour of the irradiated males of Anopheles guadrlmaculatus but Schmidt, ^ al. (1964) could not find any difference between the chemosterilized and the normal males of Musea domestica. - 10 - That flies and mosquitoes can develop resistance to chemosterilants has been shovm by Hazard, et (1964) and Patterson, ^ (1967) who found that Ae. aegypti could become resistant to the sterilant activity of apholate under laboratory conditions. Resistance to metepa has been reported in Ae» aef!:ypti by Klassen and Matsum^a (1966) and ill Miasca domes tic a by Saeca and Scirochhi (1966). - 10 - SENSITIVITY OP DYSDERCUS CIIGULATUS TO DDT, BHC MD ALDRIN AS SHOW BY DOSAGE-MORTiiLITY REGRESSION LINES Several workers have studied the effectiveness of insecticides when applied to different parts of the insect body. While all the antennal segments of the yellow mealy worm, Tenehrio molitor were highly sensitive to nicotine, the chemical when applied to the tips of the antennae of cockroaches proved ineffective (O'Kane, ^ al., 1933). It did, however, become toxic when applications were made within the first 20 proximal segments. A dose of 0.1 microgram of pyrethrins caused only 40^ knockdown in Masca domestica when applied to the thoracic terga but 100^ of the flies were knocked down when it was applied to the mouth parts (Wilson, 1949). Reddy and Naidu (1967) studied the toxicity of sevin, malathi'o'n and endrin by applying the chemicals to different parts of D. cingulatus. The mortality was highest when the chemicals were applied on the head probably because of their action on the cerebral ganglia which is a critical site for the lethal action of the insecticides. The next vulnerable site was the wing base followed by pronotum and the third abdominal sternum. There seems to be no study relating to the toxicity of DDT, BHC and aldrin when applied to different parts of P* cingulatus and hence the present tests were made. Measured - 10 - drops of pp' DDT, gamma BHC and aldrin solutions in acetone were applied topically to the head, pronotum, 1st abdominal tergum, 1st abdominal sternum and tarsi of the three-day-old adults after the manner described by Abedi (1967). The size of the drop remained constant but the concentrations varied. The treated insects were kept in 2.5 x 1.6 inch cages made of rice paper and card board. Mortality counts were made after 24 hours of insecticidal treatments. The percentage mortalities recorded in the tests were plotted on a probit scale and dosage-mortality regression lines were fitted by eye (Figures 9-11 ). The LC50 values were obtained from the regression lines by inspection and the slope of the lines was expressed as the change in probits per ten-fold change in dosage (Hbskins and Gordon, 1956). t^Z^lQl Site of application DDT BBC drin Pronotum 0,.24 8 0..0007 2 0..06 4 Head 0,• 28 0,.01 6 0,.06 4 1st abdominal sternum 0,.4 2 0,.01 9 0,.1 8 1st abdominal tergum 0.• 5 0,.02 1 0,.2 8 Tarsi 0.. 9 0..02 8 0..3 8 The results obtained show that the toxicity of the three chemicals varies with the site of application (Table 12) Pronotum was the most vulnerable site followed by the head. Of the abdominal sternum and tergum, the former was more - 60 - CO o 1 1 1 1 • • o CO H +9 g H t3 O CO o i • ! • m O CO -ci 04 CO •ri & cd +3 lO CO 1 • • 1 t 1 CO ® H CO a o <3> a \ tS ffl ei cd m J o oi • • • 1 1 1 03 o 03 H 03 H . . o CO o O -H • • • cn o i 1 1 o CO 03 o CO E^ 03 Ch • O •P o o w hH -P U H h O &3 a o a O X3 o rt Cr! W m w m 6H p^ m m PQ m m m 5• (XI H lO 0) lO LO H So lO M ^ (35 C5S OJ 00 o O H CO o O O o & o o O o o • • • • • O o o O o o - 66 - (D O to lO (0 c*- o• o« 00# # • • lo o o H o to 03 to CO 00 (!) o o 0> o CQ O « 0 03 o o o 00 CQ U3 o 05 H CO o 0) CQ 00 o CQ« 03 O o o o CQ to 03 O CQ 00 t>- CV3 O H 03 00 o CQ H O 00 O lO o CQ H 00 o 00 H C51 oa CQ 0) o o 00 00 O CQ to 00 • • • • o o CD 00 o o U3 to to O 00 00 M • • • • • • • I o o 00 lO to to o 00 00 SG f-l O) 03 03 o C\3 to H O O o 00 00 00 lO to to lO r-| iH CQ OS to 00 B lO to to I • « • • o e? CQ O to CQ O lO rH to H 00 <3> 00 ^ O «o 00 00• lO 03 o O to CO 03 CQ 03 i i o -si* 03 to 01 00 H O H H O to U3 • • • I d H O to 03 H O P3 H O to U3 i to H O 5 p u u EH I;! S •tJ EH PI m Q B « « eq 51 Q W 5! Q pq Si O PQ « U5 CV3 U3 H 03 U3 CQ to OJ o O H o 6 - 57 - o- yj 01 O • • • • O M O •H 03 ^ (0 O m 1-4 F«hi H CO to U3 O <5 to o to o U5 TO in H • CQ CO r>• O• o• CO PQ CO CO o o •H 0 W CQ IN o o H fii ® (0+3 0) o o CO 00 U3 o• H • # • o U3 CO 00 LO o o OQ (35 o o H H 0) H o to Oi lO o CO • • • a o O •H rt (3) i E^ 0> O ll H >T3 ® CM 00 o O CO to • • H "R 00 O O O• to U5 03 o 00 o O H C! O O O O • • • CO o o 00 o O) o H 03 o CO O • # • 00 o CO o T3 o U3 o CO H 05 lO o 00 o • o 00 o o 00 o H H 0) ^13 O +» PS o •H •H .s ® to 6H tJ E-t T3 Q § ^ § ^ «Q o •H CO +9 ® lO o O O o o H 00 5 - 58 - 100 FIG. 9 90 80 Ui 70 O < 60 5 50 U oe 40 UJ PRONOTUM — • «»- 30 HEAD — o 20 ABDOMINAL STERNUM •- A 10 ABDOMINAL TERGUM - A TARSI X • X 03125 0625 125 25 5 CONCENTRATION 100 FIG.ID / / 90 / / // /O / / A 80 / // UJ 70 / 0 / //A 1 60 / // A 50 / 30 PRONOTUM- /// HEAD 20 4 ABDOMINAL 4 //x STERNUM 10 ABDOMINAL A TERGUM */ / / / TARSI X 000243 .000487 000975 00195 0039 0078 015625 03125 0625 CONCENTRATION Figure 9. Dosage-mortality relationships of DDT when applied to the head, pronotum, abdominal sternum, abdominal tergum and tarsi of Dvsdercus cingulatus* Figure 10. Dosage-mortality relationships of BHC when applied to the head, pronotum, abdominal sternum, abdominal tergum and tarsi of Dysdercus cingulatus. - 64 - • 100 FIG. II 90 80 y, 70 I- 2 ^40 HI a. 30 PRONOTUM • 20 HEAD 0 ABDOMINAL STERNUM 10 --A ABDOMINAL TERGUM - -t TARSI X .015625 .03125 0625 125 .25 5 i CONCENTRATION '00 r FI6.I2 H 90 80 70 Ill 60 t- l«zl 50 ^ 40 iaa.j 30 20 ETHANOL 10 ACETONE O RISELUA OIL X ' • .01^5 .0625 .l25 .25 5 CONCENTRATION Figure 11. Dosage-mortality relationships of aldrin when applied to the head, pronotum, abdominal sternum, abdominal tergum and tarsi of Dysdercus cin^ulatus. Figure 12. Susceptibility of adults to DDT solutions in ethanol, acetone and risella oil. - 60 - susceptible to the chemleals. This may possibly be due to the location of the ventral nerve cord which is more close to the abdominal sternum than the tergum and the insecticides may have an easy access to the ventral nerve cord through the sternal plates. The chemicals were least effective when applied to the tarsi of the insects. Of ^^ the three insecticides tested BHC was the most effective. Next in order of toxicity was aldrin and DDT was the least toxic of all. The effect of solvent^was determined by applying different concentrations of/pj)' DDT, gamma BHC and technical aldrin in acetone, ethanol and risella oil on the pronotum of the three-day-old bugs. The LC50 values^ere Solvent DDT BHC Aldrin * f Acetone 0.24^ 0.00072 0.064 Ethanol 0.084 0.00033 0.023 Risella oil ^ 0.46 0.054 0.46 f Z The LcgQ values derived from the dosage-mortality regression lines (Figures 12-14) show that DDT, BHC and aldrin in alcohol were 2.95, 2.18 and 2.78 times more toxic than solutions in acetone and 5.4, 163.6 and 20 times more toxic than the solutions in risella oil (Tables 13-15). At the volume (0.0009 ccO used in/these experiments, topical - 61 - applications of ethanol alone caused a mortality of 8.3^ hro as opposed to mortalities of 0.8 and 0.58^ WspaiitXsgl^;,,,-^ by acetone and risella It ^an thus be concluded that insecticides dissolved in alcohol are more toxic to D. eingulatus than those dissolved in acetone or risella oil. This may be due to the fact that ethanol, being a powerful dehydrating agent is itself toxic to the bugs. - 62 - 100 FIG.I3 90 80 Ui geo 2 50 UK J 40 a- 30 20 /ETHANOL • 10 ACETONE O /RISELLA OIL X -L. .000121 .000243.000487.000975.00195.0039 .0078 .015625-03125 .0625 CONCENTRATION iOO r FIG. 14 0078 .015625 .03125 .0625 .|25 25 .5 CONCENTRATION Figure 13. Susceptibility of adults to BHC solutions in ethanol, acetone and risella oil. Figure 14. Susceptibility of adults to aldrin solutions in ethanol, acetone and risella oil. - 63 - o 10 to 03 H 03 00 CO O \ * HO 03O 000 ^ 0 H 0 II till \ • \ • \ • \ • 03 o o lOO U30 00 0 03 0 HO HO 030 ob 0 ^ 0 CO 0 HH H H 03H H H H H CO 00 H to to 03 00 oa O Hr- H^- COr^i Hio Ht> « H I I I i I \ • \ • \ • \ • H to 05 03 'd'OO HOO r- to 00 00 00 00 00 cHl>- Hp- 03 c^ H H 03 •o ffl H 00 0 00 H 03 10 H to O •H too r- o HO COO o3to uato ^H O• \HO . \CO .CO X \ O ^o to"© ^o U5 CO0 3 y) C-O C^ O ^ 00 m (O O E^ O CO O 50 00 10 H to bO H H HH H CO «H CO o O o CO CO 00 03 O HVO H CO COCO \ « tOH lO oao 00 00 03 \ • \ • \ • COO \ • to H'slJ 03 U3 CO 10 to ^ O O CO 10 10 03 (O 'jJ O U5 H HO HO 030 I I I I I O• \0 0 • 0\ 0 • \0 0• O 0) Ci> Q) ® +» T3 § •C ca Cn CO 03 Q U3 HtO HO CO 03 H H I I I I I I I I \ • \ • \ • (!) H O 030 O O 03 CO •H • H O M o -P © ® <0 H CO OS CtJ u H CO a e CD e 0 (xr®, !Xr®4 EH •P H a® cti JIh >0) © H H I Q> OT O O CO - 65 - to H C^ o CO 03 iOCO 00 LO o I i I II II II . \ . \ . ps. 0303 00 cd C55 ^00 !> 00 H H 0) w CO H o 05 lO to 03 us 050 H H H too t005 HOO II I I I I \ • \ • \ • \ • Pi o 00 to 03 IN COO Hto cd C5> O CJ5 05 05 05 CO to CO-^ U5 ® H H -o d ffl o H •p H lO <1> •H lO H O c; OJ ^ E^ ^ rH 00 O) U510 HOO cd I i I I \ • \ • \ • \ • \ • \ • m o U3 lo CO lO 00 00 sji 03 HH lO 03 '^Oi 00 00 03 CO H tH CO to H03 o B o H O 0> t>- ^ 5 U3 O OJ o lO CO 05 ^ 00 to CO a> eij (N3 HO C5>|>. 03U} H 03 to CO 00 too C55 03 0) CQ H• \ • \ • \ • \ • \ • \ • a § O-^O 00 00 IOC- ^PICOQ CO !>- OO w CO •H O 0)05 C^C- C-00 CO 00 C3i to -P «H H 03 (0 a 6 0) O o N 00 •H ® to O 0> C55 03 t>- I 03 Hr-4 H H E- t>- <55 O H Ui N. ' \ ' X • \ • V. • V. • t I II II 0 Wio Ui^ ^^ CO o to 00 CO 00 ^ •o 00 00 'jfoj ^o CO CO 00 O o cn 1 C •H «m o w CO CO I- •H H ^OOG IHIO HO H H 00 •P \ • \ • \ • \ • \ • \ • It II 11 F-i o H03 00 CO COCO 0300 lO O IS WCQ •H 03 r-l 00 O 03 nH •H u3 o y3vi? H^. B \ • \ • \ . I I I I I I I I i •H o 10 o tOO) Hoo +» ft H CO oa H (D O W ^ CD DDT, BHG MD jiLDRIN TOLERANCE IN DYSDERGUS GINGULATUS The number of insect species developing resistance to insecticides is mounting continuously and though much attention has been paid to pests of public health importance, the mechanism of insecticide resistance has been studied in only a few agricultural pests despite the fact that a large number of them have become resistant to one or the other group of insecticides. Since 1914, when Melander reported the failure of lime sulphur sprays for the control of Aspidiotus perniciosus, the number of resistant species has been increasing so much so that at present there are a number of species affecting agricultural or forest crops and stored products that have become resistant to chlorohydrocarbons, organophosphorus and carbamate compounds. However, unlike Insects of public health importance, pests of crops have usually become resistant to only one group of insecticides and there are only a few cases where double or multiple resistance has been acquired by these pests. Of the 115 species, 31 have Tbg^i^ie resistant to DDT and TDE, 39 to BHG and cyclodiene insecticides, 25 to organophosphates, 2 to carbamates and 18 to other insecticides (Brown, 1967) and most of these species belong to orders Hemiptera, Lepidoptera and Goleoptera. - 67 - Brazzel (1961) reported an appreciably high resistance to endrin and toxaphene in the cotton boll weevil, Mthonomus ^ rand is from Texas and the same author (1963) found a high degree of DDT resistance in the tobacco bud worm, Hellothis virescens* Both H. zea and H. virescens were observed to have developed resistance to DDT (Pate and Brazzel, 1964) and Lowry, et al. (1965) succeeded in developing 18-fold resistance to DDT in the pink boll worm, Pectinophora gossypiella in 21 generations of laboratory selection. Organophosphorus resistance has been reported in mites and smaller Hemiptera and carbamate resistance has the been found in the tobacco^]3ud worm in Texas and^light brown ^ I k^ ^ apple moth in Tasmania, j Probably because of their favoured and extensive use, resistance to cyclodiene insecticides and BHC seems to be more frequent in cotton insects such as the boll weevil and cotton leaf worm in South eastern United States, the salt marsh caterpillar and cotton leaf perforator in California, the leafworm, Frodenia litura in Egypt and the spiny boll worm in Israel (Brown, 1967). f. litura has also been reported to be resistant to BHC from Ajmer and Jaipur, India (Srivastava and Joshi, 1965). Garcia (1959) observed a considerable resistance to BHC in a strain of D. peruvianus from Viru valley, Peru, but no effort has been made to study the phenomenon in other species of this genus and hence the present work was undertaken to find out if D. clngulatus can develop any - 68 - tolerance to DDT, BHC or aldrin under laboratory conditions. Three-day-old adults were topically treated with different concentrations of acetone solutions of the desired insecticide and were kept in 2.5 x 1.5 inch cages made of riee paper and card board. They were fed on water soaked cotton seeds and mortality counts were made after twenty four hours of the insecticide treatments. The eggs obtained were bred to produce the next generation. Selection with DDT The 32.5^ survivors of 0,6% DDT were bred to produce the F-^ generation which was again subjected to insecticide pressure. In this way selection was carried upto 16th generation and the LC50 values were determined from the dosage-mortality regression lines fitted by eye. The selected strain when in the 8th and 16th generation was compared with the normal laboratory strain (Tables 16 and 17 ). The regression lines for the normal and selected strain (Figure 15) show that the species did not develop any specific resistance to DDT in 16 generations of selection. A 4-fold increase in the LC50 value unaccompanied by any fall in the slope of the lines suggests that the tolerance may be due to the accumalation of the factors responsible for vigour tolerance (Hoskins and Gordon, 1956). - 69 - O O O O CO lO • • • • o o o H o o o o o 01 0) -p +3 o •H to o H CQ o 0) 03 • • • • • • fH • o iO o 00 o ® o UQ CQ 03 to •H r-t tJ cd LO c© O O •P 03 • • • H CO o • iH 03 03 1 O e (i> O Q) ^ a a to o 03 f f «H -P 4 ^ O (D > flS H •X3 CD © •P •P^ O CO (d ® 00 u H fe Htif +3 O is; tn ay - 70 - Table 17. Lc^q levels and slopes of normal and selected strains of D. Gingulatus Insecticide Generation Lc 50 Slope DDT Normal 0.248 2.2 0.9 2.96 I'le 1.06 2.21 BHG Normal 0.00072 2.4 FS 0.00176 2.1 Fi5 0.0148 1.82 ^20 0.0131 2.3 ildrin Normal 0.064 2.1 ^12 0.129 2.1 ^16 0.18 2.16 - 71 - Selection with BHG. Selection with BHG was made at a mortality level of 81.2^ and the 18.8^ survivors of the parent generation were reared to produce the next generation. The process of selection was continued for 20 generations when the selected strain was compared with the normal one (Table 18). The increase in the LC50 (Table 17) with a corresponding fall in the slope of the regression lines (Figure 16) indicates the resistance to be of a specific type. However, the almost similar slopes of normal and the 20th generation point out that D. cingulatus is not liable to develop a high degree of BHG resistance. A tolerance of 18 times can not be considered to be very high from practical point of view and as 94.7^ kill of the selected strain was obtained with a 0.0626^ of the insecticide, it may be concluded that BHG can be safely employed for the control of D. cingulatus in India. The adults were also selected with aldrin for 16 generations (Table 19). The selected strain when compared with the normal strain showed only 3 times increase in LcgQ value (Figure 17). This suggests that the species is unlikely to develop any significant tolerance to this chemical. -12. - lO o o 00 o 00 (M • • • <£) o U3 o 00 o 03 o 00 03 O H i H lO (M 03 CO O] H • • • B CO iO 03 CO 03 CO U U5 03 t- 00 m K O• pq o o m U3 03 VO B OT M3 o• H• 03• o CD a a lO • • • o o o o CO H 03 CO 03 CD tH •H o o o lO to 10 CO 03 P H H i CC •H fl O P rt 00 03 0) O] LO sit o 03 00 CO 03 O o B « • • • o 03 o (JD o 03 to «H o # Oi OJ 03 CO CO CO H CO o 0 o p W ^ P! fH o -CJ O iO 00 b 03 03 03 H UD « • • • • « cd O lO r- CQ 00 H H CO o O) 05 O 00 03 00 00 00 Ch H B O tC H to pi C w o CO C •H uj uu vO U3 '-0 c •H -P CN3 O CO • UD 00 H H U O O) 00 CO •^Ji LO P i=l 0) «H o a o o m 0 lO -p (M iO 05 U3 03 o •H H • • • • • # • • Cli a • CO lO W 00 lO iH fM ^0^) O 00 CQ ^ PQ OT (D ch •H •"Cf -P t3 o U5 H 00 Oi O « • • • • (U 8 00 00 O CJ) LO o H lO (H 8 CQ a> •H OT C Q) -p CO fi 100 r fig. 15 90 80 oUi < 60 5 50 UoJe 40 30 20 10 .03125 .0625 .125 .25 -5 3 4 CONCENTRATION '00 r fig. 16 90 80 Ui ^ 60 5 50 UI ^ 40 oUI- 10 20 10 .00024375 .0004875 «X)975 OOI95 -0039 .0078 015625 03125 .0625 CONCENTRATION Figure 15. Dosage-mortality lines for DDT shown by normal and selected strains of Dvsdercus cin^ulatus. Figure 16. Dosage-rnortality lines for BHC shown by normal and selected strains of Dysdercus clngulatus. - 75 - 100 FIG.I7 90 80 ui ^SO ^ 40 Uoi. 50 20 10 I I 1— _1_ -1- -I- •015625 -03125 -0625 J25 ^ I CONCENTRATION Figure 17. Do sage-mortality lines for aldrin sho-wn by normal and selected strains of Dysdercus cingulatus. - 76 - BIONOMICS OF NORMAL AND BHC-RESISTANT STRAINS A number of workers have studied the differences In the bionomics of the normal and the resistant strains of insects. Pimental, et (1961) found a longer larval period in a DDT-resistant strain of Masea domestica. Other biological characteristics such as egg production, 'hatchability, larval survival and adult weight have also been shown to differ in the susceptible smd resistant strains of flies (Brown, 1968). Thomas and Brazzel (1961) compared the life history of an endrin-resistent and susceptible strain of Anthononnip i^rajadis and observed a decrease in the reproductive potential of the resistant individuals. Significant differences were observed in the fecundity and the length of time required for embryonic, larval and pupal development but the strains did not differ with respect to the mortality rates", sex ratios, length of preoviposition and oviposition periods. tPerkins and Grayson (1961) compared strains of the German cockroach, Blatella permanica resistant to lindane, chlordane and DDT with the normal strain and observed that the females of the resistant strains lived longer than the normal ones. The findings cited above mostly relate to insects of public health importance and there seems to be no published record of any studies with reference to cotton stainers. It - 77 - was, therefore, considered desirable to investigate the biological characteristics which may distinguish the BHC-susceptible and selected strains of D. cingulatus. There was no significant difference in the incubation period and the percentage hatch of the eggs of the two strains (Table 20). The duration of nymphal life, however, became shorter as a result of selection with BHG and the percentage emergence of adults was also adversely affected because of such selection. The total number of eggs laid per female also differed in the two strains being 189.7 in the susceptible strain and 145.6 in the selected one. The number of eggs laid per batch was found to be 80.2 and 67.1 in the case of susceptible and selected strains respectively. Considerable differences were observed in the preoviposition and oviposition periods of the two strains andthe longevity o_f^ the _aduljt s^ ecreased a s_ a__resul^ o f selection with BHG. While the normal males and females lived for 19.4 and 15.6 days those belonging to the selected strain survived for 15.4 and 10.0 days respectively. - 78 - -p a CO +3 o C- <£• O U3 U3 m • • • • •H 1X3 H c- 00 00 lO O V) c- H H M< «ffi CO H a O 00 o r- CV5 W '•O CO a • • • • • • • • • u LO to o o U) CD o Oi o c- CO u? CO 00 iH H M H m +3 H 03 O © fl CO H ® ® cC M bO O H S {>. M -P 0) cd ® -d e •H 0) -O •H O ffi JO ft 0} O ® CO H W) H m >> CO CO >> 0) t» m !> CO a •O o CO b ® ts ® tH T3 cC tn m X! w & H M I - 79 - SUSCEPTIBILITY LEVELS OF FIELD POPULATIONS Brazzel (1961) collected Anthonomus rrandis from 20 differerxt areas In Texas and found the samples varying in their susceptibility to endrin and toxaphene. The DDT susceptibility of Heliothis zea also varied in populations collected from different places in the state (Brazzel, 1964). During the present studies D. cingulatus was collected from seven districts of Uttar Pradesh and brought to the laboratory where they were reared for one generation in order to obtain adults of known age. When three-day-old they were tested topically with different concentrations of DDT, BHC and aldrin solutions in risella oil. Mortality counts were made after 24 hours of the treatments and Lcso values-j^ej^e" determined from dosage-mortality lines fitted by eye (Hoskins and Gordon, 1956). The results obtained (Table'21) clearly show that cingulatus is highly susceptible to BHC in various parts of the state and 0.125^ BHG ^olutions can be effecjtively used '"fo£_cpntrplling the'bugs under field conditio!^. Next in order of toxicity was aldrin and DDT was the least effective of the three chemicals tested. That the species can also be controlled with DDT is clear from the fact that the maximum Lcgo obtained with this chemical was only 0.64^. - 80 - Table 21. Susceptibility levels of field populations to DDT, BHC and aldrin DDT BHC Aldrin Place T r> Slope Slope "^60 Slope Higarh 0.33 2.3 0.02 2.34 0.149 2.41^ Allahabad 0.31 1.83 0.028 2.4 0.175 2.6 Bulandshahr 0.32 1.26 0.043 3.0 0.225 3.0 Etawah 0.316 2.21 0.023 2.68 0.196 2.73 Kan pur 0.45 1.82 0.023 2.63 0.266 2.27 Meerut 0.325 2.48 0,02 2.42 0.136 2.8 Saharsnpur 0.54 2.98 0.0186 2.48 0.113 2.1 / / / - 81 - CHEMICAL STERILIZATION OF DYSDERCUS CINGULATUS The elimination of insect population thro-agh chemosterilization has proved its superiority over the conventional methods of control hy chemicals and is gaining wide favour and popularity. Since 1955, when the first successful attempt to eradicate the screw-worm, Callitroga hominivorax from Curacao island was made "by Baumhover, ^t al. (1955), there has been a spectacular development in this field of insect control and chemosterHants have proved their worth against a large number of insect species of public health and agricultural importance. Knipling (1959, 1966) discussing the ways and means of controlling populations through the sterile male release technique pointed out that complete elimination of insect population is possible if chemosterilization is integrated with other methods of control. Hedin, et al. (1964) studied the effects of apholate on the male boll weevil, Anthonomup pr^dis and found it to be an effective chemosterilant when given in diet or when the weevils were allowed to feed on cotton plants sprayed with aqueous solutions of apholate. The most promising method of testing chemosterilants against Dlabrotica balteata consisted in exposing the adults to chemosterilant residues on glass surfaces (Creighton, ^ 1966). Oral intake of apholate, tepa or metepa did not produce - 82 - any satisfactory results whereas treatment with residual contact method caused 100^ sterility in several instances. Adults of the cereal leaf beetle, Pulema melanopus were completely sterilized when both sexes were dipped in 0.06^ aqueous solution of apholate for 30 seconds (Ezuch and Hoopingarner, 1967). Mason and Smith (1967) found that 0.6% and 1,0% apholate in bait and 0,6% apholate applied as a contact spray or as a residue on glass effectively sterilized both sexes of Drosophila melanogaster and the same compound has been found to be an effective chemosterilant of cingulatus (Mastafa and Naidu, 1964). During the present studies an effort was made to evaluate the potentiality of three aziridine compounds, apholate, tepa and metepa as chemosterilants of D. cingulatus. 0.26% and 0.6% solutions of the three chemosterilants were prepared in acetone. 6 cc. of the desired solution was sprayed on each petri dish, 3 inches in diameter. The dish was continuously rotated on the surface until dry and in this way an even film of the chemosterilant was obtained. Freshly emerged adults were released in baiwe^nr-Wse- two treated petri dishes for the desired, period of time and were then transferred to clean glass jars. Virginity of adults was self insured as copulation always started atleast two days after emergence. Sexing was, therefore, done only after treatments and single pair reciprocal crosses were established between treated and normal males and females and - 83 - also between treated males and females. Five pairs of each type were observed for the rate of oviposition and the fertility of eggs. Per cent sterility and per cent net sterility was calculated by the following formulae. Total number of unhatched eggs x 100 Total nu^^'^'^^TSId * ^ Sterility % Sterility in test - % sterility in normal ^ X 3^00 = % net 100 - % Sterility i^i normal Sterility The results obtained (Tables 22-24 ) show that all the chemicals>©©ira:3'^oducei?'Cterility in D. cingulatus -feeHs— apholate was the most effective of the three chemosterilants tb-sis^.- The males when exposed to dishes treated at the rate of 1.77 mg./sq. inch of apholate for 30 minutes and mated with normal females induced 31.8^ net sterility as against 27.4^ net sterility obtained in the case'of tepa treated males and 9.77^ in case of males treated with metepa. The rate of sterility increased when the males were exposed for a longer period and 63.6, 44.4 and 49.7^ net sterility was observed in the eggs laid by normal females after having mated with males that had y>een exposed to aphol&te^ tepa .or. metepa for two hours. The sterility was still higher when the males after having been exposed for two hours to 3.54 mg./sq. inch of the chemosterilant wete flowed to mate with normal females. - 84 - Females were less affected than the males as for as the hatchahility of eggs was concerned. A net sterility of only 35.2^ was observed in the eggs laid by females exposed to 3.54 iBg./sq. inch of apholate for two hours and mated with .no-rnial males as compared to 97.6^ net sterility where only males had been treated at the same concentration and exposure period. Treatment of both the sexes added up the' sterility effect and a higher sterility was observed in all such cases. Mustafa and Naidu (1964) exposed the adults of D. cingulatus to petri dishes treated with apholate and found that the degree of sterility varied with the concentration of apholate and the exposure time. It was also found that more eggs were laid by the females that we-re mated with males exposed to a surface containing 0.35 mgapholate/sq. inch than by the females mated with males exposed to a surface containing 1.4 mg. apholate/sq. inch. A considerable reduction in oviposition was also observed when the females were exposed to a surface containing 0.7 mg., apholate/sq. inch for 18 hours. A similar reduction in the number of eggs laid by chemosterilized females has been observed by Morgan and La Brecque (1962) in the case of Ma sea domestica. The present author, however, could not find any such reduction in the number of eggs laid by the females of D. cingulatus when chemosterili zed with apholate, tepa or metepa. - 90 - Table 22 . Effect of apholate on the fecundity and fertility of cingulatus Concentration Exposure Sex No» of eggs laid mg./sq. inch period in treated net sterility hours. Average Extremes 1.77 0.6 Male 124.0 88 164 31.8 1.77 0.6 Female 89.0 43 119 10.9 1.77 0.6 Both 89.0 27 168 47.2 1.77 1.0 Male 124.4 66 212 39.3 1.77 1.0 Female 112.6 77 162 22.9 1.7•7 1.0 Both 88.2 69 129 60.7 1.77 2.0 Male 100.4 79 163 63.6 1.77 2.0 Female 101.0 60 117 42.8 1.77 2.0 Both 69.4 23 127 66.01 3.64 0.6 Male 124.4 92 160 36.6 3.64 0.6 Female 111.6 67 209 16.7 3.64 0.6 Both 77.6 42 112 63.1 3.64 1.0 Male 67.8 21 93 43.8 3.64 1.0 Female 112.4 81 148 20.6 3.64 1.0 Both 168.2 126 192 76.6 3.64 2.0 Male 114.0 38 186 97.6 3.64 2.0 Female 79.8 46 118 36.2 3.64 , 2.0 Both 46.2 , .22 79 — — 100.0 - 86 - Table 23 . Effect of tepa on the fecundity and fertility D. cingulatus Concentration Exposure Sex No. of eggs laid % mg./sq. inch period in treated net sterility hours A%'erage Extremes 1.77 0.6 Male 208.4 171 236 27.4 1.77 0.5 Female 116.6 45 195 6.2 1.77 0.6 Both 178.6 111 237 38.3 1.77 1.0 Male 202.2 162 251 28.6 1.77 1.0 Female 164.7 109 258 16.4 1.77 1.0 Both 109.2 46 172 64.6 1.77 2.0 Male 202.5 197 208 44.4 1.77 2.0 Female 135.7 114 166 33.5 1.77 2.0 Both 89.7 41 131 76.06 3.64 0.5 Male 126.8 98 160 40.3 3.S4 0.5 Female 186.3 168 244 18.6 3.54 0.5 Both 169.0 87 226 39.9 3.64 1.0 Male 148.0 109 232 47.6 3.54 1.0 Female 192.7 141 295 30.3 3.64 1.0 Both 178.7 114 226 63.4 3.54 2.0 Male 136.0 72 213 63.5 3.54 2.0 Female 189.0 149 250 37.6 3.64 2.0 Both 129.3 106 236 66.5 87 - Table 24 . Effect of metepa on the fecundity and fertility of D. cingulatus Concentration Expo sure Sex No- of eggs laid mg./sq. inch period in treated net sterility hours Average Extremes 1.77 0.6 Male 96.0 48 172 9.77 1.77 0.6 Female 109.6 61 260 1.4 1.77 0.6 Both 101.4 43 132 37.9 1.77 1.0 Male 127.0 82 137 39.3 1.77 1.0 Female 107.2 36 172 21.4 1.77 1.0 Both 129.7 68 181 46.3 1.77 2.0 Male 96.6 62 136 49.7 1.77 2.0 Female 130.4 46 217 28.9 1.77 2.0 Both 93.6 46 142 72.4 3.64 0.6 Male 147.6 112 201 24.2 3.64 0.6 Female 93.2 77 123 9.4 3.64 0.6 Both 121.6 46 183 33.6 3.64 1.0 Male 96.6 62 131 39.3 3.64 1.0 Female 121.7 82 183 14.7 3.64 1.0 Both 120.2 76 173 38.6 3.64 2.0 Mflle 174.2 106 304 49.7 3.64 2.0 Female 76.0 48 132 30.3 3.64 2.0 Both 98.7 69 113 69.7 - 88 - PERMANENCY OF STERILITY EFFECTS OF APHOLATE, TEPA AND METEfA IN MALES AND FEMAiES OF DYSD;SRCUS CINGL^ATUS Morgan and La Brecque (1962, 1964) observed a degeneration of oocytes in the ovarian chambers of cheraosterilized houseflies and in 1961 Weidhaas and his associates observed a much high sterility in the eggs of Aedes aegypti when the females were fed on chemosterilant treated diet throughout the observation period. Dame and Ford (1964) found a gradual recovery of fertility in the males of Ae. aegypti when allowed to mate more than once. The loss of sterility was higher in apholate treated males than in those treated with tepa. Raghuwanshi (1968) found that sterilized males and females of Culex fatigans lose their sterility effect gradually. The present author exposed freshly emerged males of P* cingulatus to apholate, tepa and metepa residues on petri dishes. The chemicals were applied at the rate of 3.54 mg./sq. inch and the males after having been exposed for two hours were allowed to mate with normal virgin females of the same age by making individual crosses in rearing jars and were fed on water soaked cotton seeds. After a male had copulated once, it was removed to another tube for a second mating with another normal virgin female. In this - 89 - way each male was allowed to mate three times with a normal virgin female of the same age. The results obtained (Table 26) show that the initial sterility of the males remained more or less permanent and no significant loss could be observed in successive matings. Apholate treated males which induced 88.6% sterility in their first mating with normal females were almost equally potent in inducing 84.9^ sterility in their third mating. Similarly no recovery of fertility was observed in the case of males treated v/ith tepa and metepa. These observations are in agreement with those of Dame and Ford (1964) who found that Ae. aegypti when exposed to tepa residues developed a sterility which could not be lost even in four series of matings with normal females. The sterility developed in such cases may probably be due to direct effect of the chemosterilant on the sperms so that the destruction of genetic material by chemosterilant may leave the males permanently sterile (Smith, et al,, 1964). Tests were also made to assess the permanency effects of the three chemosterilants in the females by releasing newly emerged females in petri dishes that had previously been treated with the desired concentrations of the chemosterilants. Each female was then kept with an untreated male of the same age in a rearing tube. The number of eggs in each batch was counted and the percentage hatching of eggs in each of the three batches laid by a female was determined. - 90 - IS 0> to 00 0 oi to •H • • • • • • H 03 03 00 ^ S ^ lO to of K f-t i i i ffi tt> •P M (M O CO O B • • • • • • • • • Q> ® Cd H CO 03 to to CO H to o CO ^ e © 00 05 CO to o 00 H ® S (M H iH 03 H 03 iH 03 ft «H ® ai H iH 03 H to ui CD H i-i to ch © C5> O o 00 00 03 to O ft (xj H H H m CO M o &0 © 0 ® CVI 03 to O to CO O CO o «H CD • • • • • • • • (H u 00 03 w H 03 UD CO CO 0) o ® to to 03 00 to to > H H i-l H H H H H H • o is; iSn O o O ® 0) a & CO ft + + + + + + + + + •<0 •to •<0 liH CSi H 6H &H w +5 lO 03 § OJ •HH H ^ ® •mP EH o. i s m o EH - Is in males, the chemosterilants induced permanent sterility in females also and no appreciable recovery of fertility could be observed (Table 26). A slight increase in the hatch rate of eggs belonging to the second and the third batch was evident in cases where the females were treated with tepa or metepa at the rate of 3.64 mg./sq. inch 1 but such a recovery was not observed in the females treated with lower concentrations of these chemosterilants. The partial loss of sterility observed in the second batch of eggs laid by apholate treated females was considerably restored in the subsequent batch of eggs laid by them. It is very difficult to explain such results except to say that probably all the ovarioles of an ovary are not equally affected by the chemosterilant so that the hatch rate may differ in the successive batches of eggs laid by them. - 92 - « !—1 CO o CO H CV! LO co o o cn M yD to en o- to• 00• CO CQ 03 CO o H to H o ^ 03 O o fxO M rH oo o- txO CO -P CO o Q) CH m to CO CH EH (U <>5 05 O 00 U3 00 to to >> •P S •H 00 •H CQ H in M n H •H O -P CC•H . •p . C! CJ^ 0) CO CO - 93 - MATING VIGOUR AND SEXUAL COMPETITIVENESS OF CHEMOSTERILIZED MALES Prior to the release of sterile males for the control of an insect species in nature, it is necessary to study the effects of the sterilizing agents on the mating vigour and sexual competitiveness of such males. Any deficiency in the mating potentiality of sterile males as compared to the normal ones is likely to foil the whole attempt. This factor has, therefore, been studied by several workers but the results obtained are quite conflicting. The commendable success achieved in the eradication of screw-worm fly from Curacao island (Baumhover, et , 1966) is itself a proof of the fact that the irradiated males >ar-e almost equally vigorous to the normal ones. Davis, et al. (1959) found the irradiated males of Anopheles guadrimaculatus to be less vigorous but those of Masca domestica were found to be equally potent when treated with the chemosterilants (Schmidt, ^ al., 1964). I A significant loss in the mating vigour of the chemosterilized males of Aedes aegypti was, however, observed by Dame, et al. (1964). It seems that the effects of sterilizing agents are more or less specific and need a fuller study before larger - 94 - programmes are undertaken in the field. With this aim in view, freshly emerged males of D. ein^ulatus were exposed to glass surf ace s oiduct-l-ly treated with apholate at the rate of 3.64 mg./sq. inch for two hours. The treated males were confined in the rearing jars along with the normal males and females of the same age and were given water soaked cotton seeds as daily food. The ratio of normal and sterilized males varied in each jar. As mating starts after three to five days of emergence and the females lay the first batch of eggs about three days thereafter, observations on the egg batches and the number of eggs per batch were recorded for eight days. Each batch was kept separately and hatch rate was determined. Presuming that the treated males were as competitive as the normal ones, the expected $ sterility was calculated on the basis of proportion of sterilized males and normal males and was compared .to the $ net sterility actually obtained. The results (Table 27 ) clearly show that D. clngulatus does not lose any vigour when treated with apholate and the sterilized males are as competitive as the normal ones. This was evident when the expected sterility was''compared with the sterility actually obtained. In a test where five females were caged with five normal and five sterilized males, the % net sterility was 46.8 as against an expected sterility of 60.0^. In another series of tests where normal males were double in number than the sterilized ones - 95 - and expected sterility was 33.3^, the net sterility was 29.0^ and 34.2^. When the ratios of the treated and normal males were reversed, 62.1^ sterility was obtained. These observations do not depart significantly from the theoretical calculations and suggest that treatment with apholate has no effect on the mating potentialities of the males. A clear cut distinction could be drawn between the hatch rate of the eggs obtained from females supposed to have mated v/ith normal males and the sterilized males. In the former case the hatch rate always exceeded 80% whereas in the latter it was below 6.5^. However, there were tx-io instances where the egg batches showed intermediate rate, 43.4^ in one case and 21.1^ in another. This may have been due to the mixing of sperms from treated and normal males as multiple mating is not uncommon in this species. Dame, ^ al. (1964) observed practically similar phenomenon ii^ Ae. ae^ypti, where an increased hatch rate was obtained in the eggs laid by females that were first mated to treated males and then to untreated males. - 96 - Table 27 • Sexual competency of male D. cingulatus treated with apholate Type of mating No, of eggs No. of eggs % sterility % sterility obtained hatched expected observed 6:6:6* 643 268 60.0 46.8 6 : 10 s 10 876 664 33.0 29.08 6 s 10 s 16 927 646 33.0 34.2 10 s 6 s 16 898 303 66.0 62.1 6 s 6 s 10 743 206 60.0 68.9 6 : 0 J 5 670 12 100,0 9r7,5 * The figures indicate the number of sterilized males, normal males and normal females in each mating. - 97 - DEVELOPMENT OF RESlSTMCE TO iiJ'HOLATE The development of insecticide resistance in insects of agricultural importance has led the entomologists to find out other safer methods of control. One such method consists in the use of chemosterHants and has already shown promise for the eradication of insect populations. In 1964, however, Hazard and his associates reported resistance to aphoiate in Aedes aegypti and in 1966 Klassen and Matsumars observed metepa tolerance in the same species. Resistance to metepa has also "been indicated in housefly, Masca domestica (Sacca and Scirochhi, 1966) and recently Patterson, et (1967) observed a 20 times resistance to apholate in a colony of Je. aegypti developed by larval selection. There seems to be no study relating to the development of increased tolerance to chemosterHants in pests of agricultural importance and hence an attempt was made to find out if D. cingulatus can develop resistance to apholate under laboratory conditions. The inner surfaces of petri dishes were treated with apholate at the rate of 3.64 mg./sq. inch and freshly emerged adults were confined between them for 60 minutes. They were then removed to rearing jars and were fed on water - 98 - soaked cotton seeds. The eggs obtained were counted and reared to produce the next generation, the adults of which were again exposed in a similar manner. In this way selection was continued for five generations and the % sterility of the parent generation was compared with that of the selected ones. The results obtained (Table 28) show that the species is not likely to develop any tolerance to apholate. There was no increase in the hatch rate of eggs obtained from the females belonging to the 6th selected generation. Instead a slight increase was observed in sterility. This may be due to accumulation of genetic defects or deleterious factors in the chromosomes as suggested by George and Brown (1967) in the case of aegypti. - 99 - Table 28. Selection of D. clngulatus with apholate No. of eggs laid % hatch Generation Average Extremes Average Extremes 158.2 125 192 20.8 0.0 56.6 F. 139.0 56 212 16.3 • 0.0 42.2 122.2 79 201 10.7 5.7 16.4 F, 77.6 72 82 14.5 9.7 18.9 F. 77.2 32 103 11.6 4.4 15.6 111.0 55 190 12.8 8.2 19.6 - 100 - CONCLUSIONS Dysdercus cingulatus readily oviposited on the moist cotton seeds under the laboratory conditions. More than of the eggs were laid during the first five days of oviposition at 29°C and 60 to 10% humidity. 2. Temperature and humidity had a pronounced effect on-oviposition. The average number of eggs laid decreased with a rise in temperature and fall in humidity. Irrespective of humidity conditions the females did not oviposit a-t 15 and 40°C. 3'. The preovi posit ion period decreased from a low to high humidity and was shorter at 30°C than at 20°c. The oviposition period also decreased from a lower to an intermediate humidity but increased at the higher humidities both at 20 and 30°C. 4. The incubation period was greatly affected by temperature conditions and the threshold temperature for the development of eggs was found to lie at 10.6°C. 5. Eggs in advanced stages of development were not so adversely affected by the lower temperature as those in / the earlier stages. - 101 - 6. Of the 49 nymphs reared individijally in glass vials, 24 developed into adults at a temperature of 26.7°C while 18, 18, 14 and 15 adults were obtained from 30, 30, . 30 and 27 nymphs kept at 30.3^ 30.7, 31.0 and 33.1°c and 60 to 10% humidity. 7. In increase in the duration of nymphal life was observed with a decrease in temperature. The development took 16.79 days at a mean temperature of 33.1°C and 27.18 days at" 26.7°C. 8. Though a considerable number of the nymphs died in each nymphal instar, mortality was highest in the third instar. The nymphs failed to develop at combinations of 20^C and 90^ humidity and 30°C and 92.9^ humidity. They did not survive at 16'and 40°C. 9. The existence of five nymphal instars was checked by the formula of Dyar. 10. p. cingulatus survives on various host plants during different seasons of the year and remains hidden under fallen leaves and other debris during the months of January and February. No significant difference could be observed in the sex ratio of the adults collected from various host plants. 11. The bugs copulated freely under caged conditions and the precopulation and copulation periods varied from 3 to 5 days and 14.6 to 49.0 hours respectively at 29 + 1°C.' - 102 - The precopulation period decreased with an increase in temperature and fall in humidity and the bugs failed to copulate at 15 and 40°G. 12. Males lived longer than the females and survived from 4 to 38 days as against the females which lived for 4 to 28 days at a temperature of 29 + The longevity of the adults decreased from a low to a high humiditiy at 16°C. At 20 and 30°C, the decrease in longevity was observed from a low to an intermediate humidity -and the duration of adult life increased with a subsequent increase in humidity. / 13. Starvation resulted in an increased biotic potential but reduced the longevity of adults. The females were more tolerant to starvation and lived longer than the males. 14. The nymphal duration upto the third instar was f almost similar when the nymphs were reared on Gossypium hlrsutum, Hibiscus esculentus, fennisetum typhoides and Sorghum vulgare but differed in the fourth and fifth instars. The total duration was shorter in the case of nymphs reared on G. hirsutum and the percentage mortality of the nymphs was also lowest when they were fed on G. hirsutum. The females, however, laid highest number of eggs when reared on H. esculentus. 16". BHG proved to be most effective insecticide for the control of D. cingulatus. Of the different body parts - 103 - treated, pronotum was found to be most susceptible to DDT, BHC and aldrin solutions in acetone. Solutions of DDT, BHC and aldrin in ethanol were more toxic as compared to similar solutions in acetone or in risella oil. 16. When reared under insecticide pressure, the adults developed a tolerance of 4, 18 and 3 times the normal to DDT, BHC and aldrin respectively in 16, 20 aiid 16 generations of selection under laboratory conditions. 17. The number of eggs laid per female was higher in the normal strain than in the BHG-resistant strain and the adults belonging to the normal strain lived longer than the BHC-resistant ones. 18. Field populations collected from different parts of Uttar Pradesh were found to be susceptible to DDT, BHC and aldrin suggesting that the species hg.s not developed any tolerance to chlorinated hydrocarbons insecticides in the field. 19. Apholate was found to be an effective chemosterilant of D. cingulatus. Males were more susceptible to the sterility effects of the chemicals than the females. 20. Treatment of males with apholate had no effect on their mating vigour and sexual competitiveness and they were as competitive as the normal ones. 21. The species did not show any tolerance when selected with apholate for five successivB generations in the laboratory. - 104 - SUMMARY " Dysdercus cingulatus is a well known pest of cotton and vegetables In India. Both the nymphs and the adults suck the sap of the host plants and stain cotton fibres by their excreta. The species has also been reported to introduce a bacterium, Nematospora gpssypii into the cotton bolls. During the present studies the females of D. cingulatus readily oviposited either at the bottom of petri dishes or in small crevices in between the cotton seeds under laboratory conditions. The eggs were laid singly one after the other at intervals of 40 to 50 seconds each and were later arranged into batches with the help of the hind legs. The whole process took 1.5 to-2.0 hours. The number of eggs laid per female per day was calculated by keeping 11 pairs individually in glass tubes at 29 + 1°C and 60 to 10% humidity. More than Ibfo of the total eggs were laid during the first five days of s oviposition during which period none of the females died. Temperature and humidity conditions had a marked effect on oviposition. The average number of eggs laid by the females decreased with a rise in temperature and fall in humidity. At a temperature of 40°C the females died within 24 hours of emergence without laying any eggs while at 15°G they lived for 16 to 35 days without any oviposition. The preoviposition - 110 - period decreased from a low to the high humidity and was shorter at 30°G than at 20°C. Similarly the oviposition period also decreased from a lower to an intermediate humidity but increased at higher humidities. The duration of oviposition period was, however, longer at 20°c than at 30°G. 'The post oviposition period was comparatively shorter and the females died in 1.3 to 2.6 days after the deposition of the last batch of eggs. The eggs of D. cingulatus are oval in shape and measure 1.119 x 0.846 mm in size. When freshly laid they are white in colour but become yellowish and finally orange in 32 to 36 hours. The percentage hatch and the incubation period of the eggs were studied at 15, 20, 25, 30 and 40°G and at various humidities. The percentage hatch of eggs was lower at humidities below 50^ than at higher , humidities and the threshold temperature for the development of eggs was found to lie at 10.6°C. The eggs failed to hatch at 15 and 40°G Irrespective of humidity conditions. Eggs belonging to different age groups when refrigerated for 24, 48, 72, 96 and 120 hours at 10°G in a refrigerator with the humidity ranging from 44 to 47^ were found to be greatly affected by the refrigeration period. The eggs in early stages of development are more adversely affected by the lower temperatures than those in advanced stages of development and the usual incubation period of 6.8 days increased to 10 days when 72 hour old eggs were refrigerated for 120 hours. ,- 106 - The nymphs were reared individually at mean temperatures of 26.7, 30.3, 30.7, 31.0 and S3.1°C and 60 to 70^ humidity in small celluloid tubes. 24 adults could be obtained from the 49 nymphs reared at a temperature of 26.7°G while 18,18, 14 and 15 nymphs transformed into adults from the 30, 30, 30 and 27 nymphs kept at 30.3, 30.7, 31.0 and 33.1°C respectively. The nymphal duration took 16.79 days at -a temperature of 33.1°G but became 27.18 days at a temperature of 26.7°C. The highest mortality of 66.6^ was observed in the third instar nymphs reared at 30.3°G. Observations on the combined effects of temperature and humidity on the development of nymphs showed that the development was much slower at 20°c and 66^ humidity with a high percentage survival than at 30°c and 63^ humidity. Irrespective of temperature, higher humidities are unfavourable for nymphal development so much so that at 20 and 30°G and 90 and 92.9^ humidities they died in 4 to 6 and 2 to 5 days respectively. The nymphs failed to develop at 15 and 40°G. The existence of five nymphal instars was checked by the formula of Dyar (1890) which utilizes the ratio of increase in the width of head capsule in successive instars as a factor for determining the number of instars in the life cycle of an insect. The calculated widths were close to the measured ones suggesting thereby that no ecdysis had been overlooked. - 107 - The nymphs pass through five Instars. The first instar nymphs are short, oval in shape. Three small openings of stink glands are present on the inter-tergal membranes of 3/4, 4/6 and 5/6th abdominal segments which are retained thro-ughout the nymphal life. The proboscis extends upto the 1st abdominal segment. In the second instar nymphs the proboscis extends upto' the end of abdomen and in the third instar it extends upto the third abdominal segment only. It is still shorter in the fourth and fifth instars, extending only upto the 2nd abdominal segment. The wing pads appear in the third instar and in fourth instar nymphs white bands appear on the 2nd, 3rd, 4th and later on the 6th sternal plates. The fifth instar nymphs are characterized by the presence of white bands from the second to- the sixth abdominal sterna. Pysdercus clngulatus attacks a number,of plants during different seasons of the year. It is found on the a rosea from March to May and on Hibiscus esculentus from July to September or October. The bugs are active Gossypium hirsutum from September to December and then hide themselves under the fallen leaves and other debris during the months of January and February. There was no difference in the relative abundance of males and females collected from different plants. ' The bugs copulate freely under caged conditions. Of the 30 pairs observed, 17 copulated after 3 to 5 days of - 108 - emergence. The process took 14.5 to 49.0 hours. The precopulation period decreased with an increase in temperature and fall in humidity and no copulation could be observed at 16 and 40°C. The males lived for 4 to 38 days and the females for 4 to 28 days at a temperature of 29 + 1°C. The longevity decreased from a low to a high humidity at 15°C but at 20 and 30°C, it decreased from a low. to an intermediate humidity and then increased with a subsequent increase in humidity. While the maximum longevity of 42 days was observed in males at 20°c and 66 and 90^ humidities, the adults died within 24 hours of emergence at 40°G. Freshly emerged adults were starved for varying periods of .time in glass tubes at 29 + 1°g and 60 to 70^ humidity. All of them survived a starvation period of 48 hours but 85 and 100^ of the adults died when starved for 120 and 144 hours respectively. The 15^ adults that survived a starvation period of 120 hours were bred to produce the next generation and were again starved for the same period. The selection was continued for five generations. The number of eggs laid per female increased 4 from 82.5 to 194.6 in five generations of starvation but longevity decreased from 23 and 24 days to 20.4 and 21.9 days in the case of males and females respectively. That the adult became resistant to starvation is clear from the fact that while 85% adults died when starved for - 109 - 120 hours in the parent generation, 0.0^ mortality was obtained at the same starvation period in the fifth generation. The females were more tolerant to starvation and lived longer than the males. Newly hatched nymphs were reared on four different kinds of plant foods and the adults obtained from them were also fed on the same diet. The development u'pto the third instar was almost similar on all food plants but variations were observed in the duration of the fourth and fifth Ins tars. reared on G. hirsutam while only 50.0, 61.1 and 48.0^ adults were obtained from the nymphs fed on H. esculentus. typhoides and S. yulgare respectively. All the females reared on G. hirsutum laid the eggs while 30.0, 16.4 and 22.3^ of the females reared on H. esculentus. F. typhoides ajid S. vulgare did not oviposit. As many as 106.4 eggs per female were laid when the females were fed on pods of H. esculentus. The hatch rate of the egg^i was higher when reared on G. hirsutum and H. esculentus than on P* typhoides and S. vulgare. The efficiency of DDT, BHC and aldrin against clngulatus was tested by topical applications of acetone solutions of the insecticides on the body of three-day-old adults. The results obtained showed that irrespective of the site of application, BHC was the most toxic of the three chemicals. Of the different body parts treated, - 110 - pronotum was found to be the most susceptible followed by the head, abdominal sternum and tergum. The insecticides were least effective when applied to the tarsi. The effectiveness of these chemicals in ethanol, acetone and risella oil was also evaluated and in all cases solutions in ethanol were more toxic than those in acetone or in risella oil. Three-day-old adults were also selected with solutions of DDT, BHC and aldrin in successive generations of rearing. Selection with DDT was continued for 16 generations and the Lc^q values obtained for the selected and the normal strains showed a 4-fold increase in the DDT tolerance as against a tolerance of 18 times observed when the adults were selected with BHC for 20 generations. When subjected to aldrin pressure for 16 generations, a tolerance of only 3 times the normal was developed. Pressurization with BHC has a significant effect on the bionomics of D, cingulatus. The number of eggs laid per female was 189.7 in the normal strain and 145,5 in the resistant one. The differences between the tvio strains as regards the incubation period and percentage hatch of eggs were insignificant 'but the duration of nymphal life was longer in the normal strain, A higher percentage of nymphs belonging to the normal strain developed into adults. The two strains also differed in the longevity of adults. While the normal males and females lived for - Ill - 19.4 and 15.6 days, the BHC - resistant adults died after 16.4 and 10.0 days of emergence. The susceptibility of field populations of cingulatus to DDT, BHC and aldrin was determined by collecting the adults from different parts of Uttar Fradesh and rearing them for one generation in the laboratory in order to obtain adults of uniform age. It was found that 0.125^ BHC in risella oil could be effectively used for the control of the species in the field. The sterility effects of three aziridine compounds, apholate, tepa and metepa were studied by making reciprocal crosses between the treated males and normal females, treated females and normal males and treated males and females. Newly emerged adults were exposed to petri dishes treated with 1.77 and 3.54 mg./sq. inch of the desired chemical. Apholate was found to be the most promising chemosterilant of D. cingulatus. When allowed to mate with the normal females, the treated males retained their sterility during successive matings. The chemosterilants also induced a permanent sterility in the females and in cases where the treated females were mated with normal males the hatch rate of the eggs belonging to the 2nd and 3rd batches was almost the same as that of the 1st batch. The males treated with apholate were found to be as vigorous and sexually competitive as the normal ones. - 112 - Selection of adults with apholate for five generations did not induce any tolerance to the chemical and no significant difference could "be observed in the sterility of the parental and the selected generations. - 113 - ACKNOWLEDGEMENTS The author wishes to express his most sincere gratitude and appreciation to IProfessor Nawab H. Khan for his kind help and valuable guidance during the progress of research, without which this work would never have come to light. Particular indebtedness is due to late Professor M.1. Basir Khan for permitting the author to work in the Department arid for providing necessary- facilities. Special thanks are due to Professor S.M.ilam, Head of the Department for the persistent encouragement and invaluable aid throughout the work. The author is also thankful to all his teachers and friends especially to Dr. M.M. igarwal for his advice and suggestions whenever needed and to his colleague, Mr. O.P. Raghuwanshi for the continuous help and encouragement during this work. The author is also indebted to Dr. A.B. Borkovec, in charge, Chemosterilant investigations, USDA, Beltsville, Maryland for kindly supplying the chemosterilants, apholate, / tepa and metepa. - 114 - Thanks'are also due to Council of Scientific and Industrial Research, New Delhi for the award of a Junior Research Fellowship which enabled the author to complete his studies at Aligarh. - 115 - REFERENCES Abedi, Z.H. 1957 Insecticide resistance in the Indian Housefly, Misca domestica nebulo Fabr, C.R.S® Congres de La P.I.O.S.A., Tananarive, section B, 85-90. Ballard, E. and Evans, M.G. 1928 Dysdercus sidae. Montr., in Queensland. Bull, ent. Res. 18 (4)$ 405-432. Banerjee, S.N. and Basu, A.C. 1955 Effect of tetrax-l, A systemic Insecticide on red cotton Mg, Dysdercus cinp:ulatus Fabr. in West Bengal. Science and Culture. 205 599-600. Barbosa, A.J.S. 1950 A comparative study of bionomics of cotton stainers in Mozambique and measures for their control. Portug. 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BY Islam Ahmad ABSTRACT Dysdercus cingulattis is a serious pest of cotton and other crops in India. Both the nymphs and the adults suck the sap from the leaves and green cotton bolls and attack young oily seeds rendering them unfit for sowing. The species has also been reported to introduce a bacterium, Wgmatospora gossypii into the bolls. But inspite .of all its Importance, very little i's knovjn regarding the bionomics of the insect and very little has been accomplished with respect to its control. . The present work was, therefore, undertaken to study the effects of ecological factors influencing the activities of the species and to find out if it can be effectively controlled by the use of chemicals that have been successfully employed against other related pests. An attempt has been made to study the development of BHG resistance in the species. The efficiency of the com.monly used aziridine compounds, apholate, tepa and metepa as chemosterilants of D. cingulatus has also been evaluated. The females readily oviposited either at the bottom of Petri dishes or in small crevices in between the cotton seeds under •ya« laboratory conditions. The eggs were laid singly one after the other at intervals of 40 to 50 seconds each and were later arranged - 2 - • into batches by the females with the help of the hind legs. The •whole process took 1.5 to 2.0 hours. More than 75% of the eggs were laid during the first five days' of oviposition period at 29 + 1°C and 60 to 70% humidity. During this period none of the females died. Temperature and humidity conditions had a pronounced effect on oviposition. The average number of eggs laid by a female decreased with a rise in temperature and fall in humidity. The females died within 24 hours of emergence at 40°C and in 16 to 36 days at 15°c without laying any eggs. The preoviposition period decreased from a low to the high humidity and was shorter at 30°C than at 20°c. The oviposition period decreased from a lower to an intermediate humidity but increased at higher humidities. The post oviposition period was short and the females died in 1.3 to 2.6 days after the deposition of the last batch of eggs. The percentage hatch and the incubation t)eriod of the eggs was studied at 15, 20, 26, 30 and 40°C and at various humidities. The percentage hatch of the eggs was lower at humidities below 50% than at higher humidities. The threshold temperature for the development of eggs was found to lie at 10.6°C. Irrespective of the humidity conditions, the eggs failed to hatch at 15 and 40°C. Eggs of different age groups when refrigerated for 24, 48, 72, 96 and 120 hours at 10°C and 44 to 47^ humidity were found to be greatly affected by the refrigeration period. The eggs in early stages of development asae more adversely affected by tira lower temperatures than those in advanced stages of development and the usual incubation period of 6.8 days increased to 10 days when 72 hour old eggs were refrigerated for 120 hours. - 3 - • The nymphs were reared individually at mean temperatures of 26.7, 30.3, 30.7, 31.0 and 33.1°G and 60 to 70,^ humidity. Of the 49 nymphs reared at a laboratory temperature of 26.7°C, 24 adults were obtained but only 18, 18, 14 and 15 nymphs transformed into adults from the 30, 30, 30 and 27 nymphs kept at 30.3, 30.7, 31.0 and 33.1°C respectively. The total nymphal duration was found to be 16.79 and 27.18 days at ifee temperatures of 33.1°C and 26.7°C respectively. The highest mortality of 66,6% was observed in the third instar nymphs reared at 30.3°G. Studies on the combined effect of temperature and humidity on the development of nymphs showed that the development was much slower at 20°C and 66^ humidity with a high percentage survival than at 30°C and 63^ humidity. Irrespective of temperature, higher humidities ssfewevc unfavourable for the nymphal development. The nymphs failed to develop at 15 and The existence of five nymphal instars was further checked by the formula of Dyar (1890). The first instar nymphs are short, oval in shape with three small openings of stink glands on the inter-tergal membranes of 3/4, 4/6 and 6/6th abdominal segments which are retained throughout the nymphal life. The proboscis in this instar extends upto the first abdominal segment while in second instar nymphs it extends upto the end of abdomen and in third instar it is upto the third abdominal segment only. In the fourth and the fifth instars it is still shorter, extending only upto the second abdominal segment. Wing pads appear in the third instar and in fourth instar nymphs white bands appear on 2nd, 3rd, 4th and later on the 5th sternal plates. The fifth instar nymphs are characterized by the presence of white bands from second to sixth abdominal sterna. _ 4 - S- clngulatus feeds on different host plants during the year. It attacks Althea rosea from March to May,, Hibiscus esculentus from July to Septeraber or Octoher and Gossypium hirsutum from SepteTiber to December. The bugs hide themselves under fallen leaves and other debris during the months of January and February. No difference was, however, observed in the relative abundance of the males and the females collected from different host plants. The bugs copulate freely under caged conditions. Out of 30 pairs kept under observation, 17 copulated after 3 to 6 days of emergence. The process took 14.6 to 49.0 hours. The precopulation period decreased with aji increase in temperature and fall in humidity. The insects did not copulate at 15 and 40°C. The longevity-of the adults was found to vary from 4 to 38 days in males and 4 to 28 days in females at a temperature of 29 + 1°C. The longevity was also determined at different temperatures and humidities. It decreased from a low to an intermediate humidity and then increased with a subsequent increase in humidity. was The maximum longevity of 42 "days/observed in the case of males at 20"c and 66 to 90^ humidity. The adults died within 24 hours of emergence at 40°C. Resistance to starvation was studied by keeping freshly emerged adults without food and water for varying periods of time in glass tubes at^ 29 + 1°G and 60 to 70% humidity. KLl of them Iht ^ sxirvived a starvation period of 48 hours, is^t Ibfo adults that survived a starvation period of 120 hours v/ere selected and bred to produce the next generation. They were again starved for the same period and selection vas continued for five generations. was That the adults became resistant to starvation is clear from the fact that while 86% adults died when starved for 120 hours in the - 5 - • parent generation, 0.0% mortality was obtained at the same starvation period in the fifth generation. The number of eggs laid per female increased from 82.5 to 194.6 but' the longevity decreased from 23 and 24 days to 20.4 and 21.9 days in males and the females when selected for five generations. The effects of different plant foods on the developriBnt, fecundity and fertility v/ere studied by breeding D. cingulatus on w u, Gossypium hirsutum, Hibiscus esculentus, Pennisetum typhoidels and Sorghum vulgare in the laboratory. It was found that <62% nymphs developed into adults when reared on G. hirsutum while only 50.0, 61.1 and 48.0^ adults were obtained from the nymphs fed on H. esculentus, P. typhoides and S. .vulgare respectively. Ill the females reared on G. hirsutum laid the eggs while 30.0, 15.4 and 22.3^ of the females reared on H. esculentus, typhoides and S. vulgare did not oviposit. Is many as 106.4 eggs per female were r laid when reared on the pods of H. esculentus. The hatch rate was higher when reared on G. hirsutum and H. esculentus than on other diets. The efficiency of DDT, BHG and aldrin when applied to different parts of the insect body was determined. It was found that irrespective of the site of application, BHG was most toxic to the adults and DDT the least toxic. Of the various body parts » treated, pronotum was f-ound to be most susceptible to all the chemicals tested. The effectiveness of the three chemicals in ethanol, acetone and risella oil v/as also evaluated and in all cases the insecticides when dissolved in ethanol were more toxic th;in those in acetone or in ri sella oil. Three-day-old adults were also selected with-DDT, BHG and aldrin. The species developed a tolerance of 4, 18 and 3 times the - 6 - normal to DDT, BHG and aldrin respectively in 16, 20 and 16 generations of laboratory sel€5Ction. Selection with BHG had a marked effect on the bionomics of p. cingulatus. The number of eggs laid per fem.ale was 189.7 in the normal strain and 145.5 in the resistant one. The duration of nymphal life was also longer in the normal strain. Adults belonging to the normal strain lived for 19.4 and 16.6 days as compared to the resistant ones that died after 15.4 and 10.0 days of. emergence. 'Populations of D. cingulates collected from different parts of Uttar 'Pradesh were reared for one generation in the laboratory ,and the progenies when three-day-old were tested for their susceptibility to DDT, BHG and aldrin. None of the samples tested, hov;ever, showed any tolerance to these chemicals. The aziridine compounds, apholate, tepa and metepa were tested as chemosterilants of D. cingulatus. Apholate v/as found to be the most effective chemosterilant and metepa was the least effective. The treated males retained their sterility during successive matings with normal females. The chemosteriil^nts also induced a permanent sterility in the females and in cases whei'e the treated females v;ere mated with normal males the hatch ra":e of the eggs belonging to the 2nd and 3rd batches was almost the same as that of the 1st batch. The species did not show any tolerance when selected with apholate for five successive generations in the laboratory. fH OlO 03 HOT H 00 oaoo H^ COtO H W H H ba a cd o OJe^ -p T-i a -P ® CO o CO CX3 H u •P U3 O © H 00 03 o Oi C3 H 0 P! 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