Journal of the American Mosquito Control Association, l0(l);24-28, 1994 Copyright @ 1994 by the American Mosquito Control Association, Inc.

OVPOSITION, HATCHING, AND AGE COMPOSITION OF A PESTIFEROUS MIDGE. PARIPES (DIPTERA: )'

RUI-DE XUE, ARSHAD ALI ,C'NDRICHARD J. LOBINSKE universitv*fi"^i'f ;!,'tf ,:';x:"t:;'::,:;:"ff !;ndEoducationcenter'

ABSTRACT. Field-caught gravid female in central Florida laid a single egg mass each during onset ofphotophase in laboratory cages. Egg masses averaged 626 and 942 eggs/mass during summer and spring, respectively. Oviposition preference in water was not detected when provided from different sources (i.e., distilled, tap, ponds and a lake). However, the percentage ofegg hatch/mass was significantly (P < 0.05) higher in the lake water than in water from the other 3 sources. Observations on follicular development in the ovaries indicated presence of t/zL/r yolk within 2 days, full yolk at >2 days, and parity at -4 days postemergence. Age composition of field-collected G. paripes populations from June to December 1992 was 29o/oat <2,48o/o al >2, and23o/o at >4 days old, and paity 23o/o. Adult abundance was correlated with prevailing air temperatures in the study area.

INTRODUCTION MATERIALS AND METHODS In recent years, adult chironomid midges Adult G. paripes were collected on multiple emerging from some urban natural or man-made occasions during June 1992 and May 1993 from aquatic habitats have increasingly posed a va- the Lake Monroe Marina area of Sanford using riety of nuisance, economic, and, in some situ- a hand-held sweep net. A battery-operated as- ations, medical problems to human populations pirator was also used to capture adults resting on worldwide (Ali 199 l). In central Florida, the city lakefront walls and other structures. Collections of Sanford has been plagued by Glyptotendipes were usually made between 1300 and 1600 h paripes Edwards and Chironomus crassicaudatus EDT and the captured adults were released into Malloch midges for many years (Ali 1980)' It has a screened cage (56 x 56 x 56 cm) and were been documented that Sanford suffers an annual transported to the laboratory. After acclimating economic loss of $3-4 million because of phe- the caged adults for l-2 h in a control room (air nomenal midge swarms frequently emerging from temperature 25-27"C and 14:10 h light:dark), adjacent Lake Monroe (Anonymous 19772).Be- 100 females were collected with a mouth aspi- cause of the recurring economic loss and nui- rator and released into a standard mosquito cage sance posed by adult midges, chironomid re- (3 I x 3l x 3l cm). A plastic cup (15 cm diam search in the Sanford area is being continually x 4 cm high) containing about 300 ml tap water conducted and the results have been reported in was left in the middle of the cage for the gravid several recent publications discussed by Ali females to oviposit into. For the next 3 days the (199 l). We present here laboratory observations cups were examined daily and any egg masses on G. paripes oviposition behavior, fecundity, laid were removed with a dropper and the num- egg hatch in different water types, and follicular ber of egg masses recorded. Each egg mass was development. Also reported are agecomposition transferred to a Sedgwick-Rafter counting cell and parity of adult G. paripes collected from the containing 2-3 drops of distilled water and dis- Sanford area. Such biological and ecological un- sected to count the number of eggs. derstanding is essential for the overall develop- To observe oviposition behavior of G. paripes ment of criteria for midge control. in the laboratory, 20 field-collected gravid fe- males were placed individually in labeled 250- ml glass beakers containing 100 ml distilled wa- ter. The mouth of each beaker was covered with a l-mm nylon mesh secured with a rubber band I is Florida Agricultural Experiment Stations This to confine the adult to the beaker. Each adult was Series No. R-03290. Journal through the mesh hourly for the first 2 Anonymous. 1977. Economic impact statement, examined at 34 h intervals until blind mosquito (midge) task force. Sanford Chamber 24 h and subsequently of Commerce, Seminole CountY, FL. its death. The study was repeated 3 times. 24 Menor 1994 Ovtposlnox eNo Fsc[rNDrry or A CnrroNoIvrIo 25

Table l. Mean number (+SD) of eggs/egg mass laid by field-collectedt Glyptotendipes paripes under caged laboratory conditions (25-27"C, l4: l0 h light: dark). Eggs were laid in tap water. Season Mean + SD Range Summer (June-July I 992) 626 + 2t9 295-l,I 50 24 Spring(April-May I 993) 942 + 229 42{U-.r,400 52 ' Adults collectedfrom lakefront structures(Lake Monroe), Sanford, SeminoleCounty, FL.

Oviposition preference of G. paripes in water of the ovaries were classified according to De- derived from 4 sources (distilled, tap, experi- tinova (1962)and Seward(19803). mental ponds [Ali et al. 1993], and lake Monroe) Age composition of female G. paripes fielc was studied in the laboratory. These were the populations was determined by collecting adults candidate water types for future laboratory rear- on a monthly basisfrom Juneto November 1992, ing of G. paripes. All water types were aged for from lakefront locations in Sanford.One hun- 24 h before use. Four labeled paper cups (7 cm dred to 300 randomly selectedfemales were ex- diam x 4 cm high) containing about 75 ml of amined monthly in the laboratoryto determine each water type were placed in the middle of the parity statusand yolk development.To confirm mosquito cage containing 100 field-collected fe- the female age in these populations, field-col- male G. paripes. The females in each cage were lected larvae of G. paripes from l-ake Monroe allowed to lay their egg masses in the cups for a were reared to the adult stagein the laboratory period of 24 h after which each cup was examined (Biever 1965).The adults were dissectedat l. for egg masses. The study was repeated 4 times 1.5,2, 3,4, and 5 dayspostemergence to observe and each time the site ofa cup containing a water presenceofyolk in primary follicles(Fischer 1969) type was changed so that it occupied all 4 posi- and compared with that of the field populations. tions. Water pH, dissolved oxygen, salinity, anc Laboratory-determined monthly percent parity conductivity of each water type in the cups were of field-coflectedG. paripes was compared to G. determined prior to placement of the cups in the paripes population abundance in the field esti- cage. mated by utilizing 2 New Jerseylight traps per- The number of eggshatching in each of the 4 manently placed,at 2 separatelakefront locations water types was studied for 72 h in I cm diam and monitored weekly from June to December x l0 cm long test tubes. The incubation period 1992. Air temperature and rainfall data in the for most chironomids is 2-5 days depending upon areawere collected from June to December 1992 the water temperature (Branch and Wichita 1923). at a weatherstation at the University of Florida's One freshly laid (within l2 h) egg mass was placed Central Florida Researchand Education Center, in each tube to which water of one type was Sanford. added to bring the total volume to 5 ml. Each The collecteddata in various experimentswere treatment was replicated 6 times. After 3 days, analyzedby chi-squareand ANOVA. A log(n + the contents of each tube were examined at 40 x l) transformation was used where deemed nec- using a binocular microscope fitted with a Whip- essary. ple ocular grid. The contents were examined by taking small portions in a Sedgwick-Rafter cell. RESULTS The hatched larvae and the unhatched eggs in each tube were counted. Percent egg hatch was Field-collectedfemale G. paripeslaid only one calculated by the following expression: eggmass during its adult life in laboratory cages. The mean number ofeggs/masswas 626 and 942 during summer TLH and spring, respectively (Table o/ohatch: " too l). TLH + NHE The gravid females contained in beakerslaid egg massesonly in the morning within a few where: TLH : total larvae hatched; NHE: non- minutes of the onset of photophasein the lab- hatched eggs oratory. These females rested on the glass wall The parity percentage and primary follicle stage of nulliparous females was determined by dis- secting field-collected G. paripes to remove the 3 Seward,R. M. 1980. A study of fecundity in the ovaries, which were then examined under 100 x Chironomidae, with emphasison intra- and inter-spe- of a compound microscope. Stage of follicular cific variability in primary follicle number. Ph.D. dis- development and nulliparous and parous status sertation, University of Pittsburgh, PA. 26 Jounner on rns AuenrcnN Mosqurro Corvrnor Assocr,c.Tror,l Vol. 10, No. I

Table 2. Oviposition of field-collectedt Glyptotendipesparipes in the laboratory (25-27"C, l4:10 h light: dark) in water obtained from different sources(types), and selectedchemical parameters of each water type. Means in columns followed by the same letter are not statistically different (P > 0.05). Mean values + SD Selected water parameters o/o D.O. Salinity3 Conductivity4 Water type oviposition2 pH (ppm) (v*') (pmhos/cm) Distilled 23 ! 4.7 6.35+ 0.2 8.7 + l.l 0.0 + 0.00a 10.4+ 0.90a Tap 15+ 1.4 6.50+ 0.4 7.2 + o.7 0.4 + 0.13b 368 + 52.0b Pond 26 + 4.1 6.98+ 0.5 3.8+ 1.2 1.1+ 0.ll c 1,590+ 195.0c Lake Monroe t6 + 2.2 7.70+ O.7 7.5+ 0.5 1.0+ 0.00c 1,340+ 89.0d t Adults collectedfrom lakefront structures(I-ake Monroe), Sanford, SeminoleCounty, FL (June-August 1992) 2 x2:4.79, df : 12,P > 0.05. 3F = l23.df: 3 and 12.P < 0.01. aF: 160.df:3 and 12.P < 0.01.

or the water surface and within I min gradually lected populations that could not be separated. released all the eggs in one mass. The brownish Chemical parameters of water, particularly sa- eggs were enclosed in a translucent gelatinous linity and conductivity were significantly (P < substance and the entire mass was ca. 3 mm 0.0 I ) different for the different water types (Table when freshly laid. Some females with egg masses 2), but apparently had no influence on oviposi- had to vigorously for shaking their abdomen tion of G. paripes. to separate the egg mass from the abdomen tip. The eggs hatched in all 4 water types. Percent The laid egg masses settled onto the beaker bot- egg hatch/mass was significantly higher (P < 0.05) tom within a few seconds and after about 5 min in the lake water than in the other 3 water types enlarged from 3 mm to ca. 1.2 cm. The parous at72h (Fig. l). The range of percent egg hatch/ females died within 2-3 days of oviposition. mass varied from a minimum of 25o/oin distilled G lyptotendipes paripes laid eggmasses in water water to a maximum of 44o/oin the lake water. derived from all 4 sources (types) (Table 2). Per- This range of egg hatch at 72 h was rather low. cent oviposition in water from experimental It is likely that eggs of G. paripes hatch beyond ponds was the highest as compared to the other 72 h postoviposition. 3 water types, but this difference was not statis- Follicular development in laboratory-reared tically significant (P > 0.05). In general, this spe- G. paripes indicated presence of Yr-3Ayolk within >4 cies had rather low oviposition rates in the lab- 2 days, full yolk at >2 days, and parity at oratory. This was most likely due to large days postemergence. Based on laboratory obser- proportions of parous females in the field-col- vations, the age composition of total field-col-

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WATERSOURCE (ryPE) 1992 Fig. l. Percentegghatch/eggmassoffield-collected Glyptotendipesparipes laying egg massesin the labo- Fig. 2. Percent age composition of nulliparous ratory (25-27"C air temperaturesand 14:10 h light: Glyptotendipes paripes (June-November I 992) occur- : dark) in water derived from 4 different sources(types). ring at lakefront,Lake Monroe, Sanford,FL (x2 20.25, Barsindicate SD values(x':9.16, df: 3, P < 0.05)' df:6.P<0.01). Mencn 1994 OvrpostrroN N.rp Frcur.rDITY or I CrunoNolrarp 27

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250 30 F I \ + NUMBEBOF ADULTS o J -r- PARITY 2 200 R 24 .-\o_f._.\_-O .. .r U) 1' F t\ ,'\ m a' t 2'< 1so \-'\t\/'\\ 188 uo \/\' \/\l z \/\l { \/\l 9t \/\r ! \/\l ;f 1oo t------r \ . 12 I ut

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JUN JUL AUG SEP ocT NOV DEC

1992 Fig. 3. Adult abundanceand parity of Glyptotendipesparipes (June-December1992) occurring at lakefront, I-ake Monroe, Sanford, FL (Parity x2: 44.23, df : 6, P < 0.01). Mean air temperaturesand monthly mean rainfall in the Sanford area from June to December 1992 are also shown.

lected female G. paripes from June to November October, declining rapidly in November and De- I 992 was 29o/oat < 2 days, 48o/oat > 2 days, and cember. 23o/oat >4 days old. In this population, nullip- arous G. paripes were 380/oat <2 days and 620/o DISCUSSION at >2 days old. Monthly age composition of <2 days old nulliparous freld populations of G. pari- Details concerningfecundity, oviposition be- pes changed from 49o/oin June to l9o/o in No- havior, egg hatch, and age composition of field vember (Fie.2). populations of G. paripes were previously lack- Monthly percent parity of field-collected G. ing, although cursory observations on the life paripes observed from June to November 1992 history (Lieux and Mulrennan 1956) and ovi- ranged from a maximum of 29o/o(June) to a min- position(Nielsen 1962) of this specieshave been imum of l2olo(August) (Fig. 3); the mean percent reported.Nielsen ( I 962) observedthal G.paripes parity for the 6 months amounted to 23o/o.Drtr- laid egg massesin the field at the end of civil ing this period the mean number of adult G. twilight. In our laboratory observations,G. pari- paripes in the New Jersey light traps fluctuated pes did not lay eggsin the eveningor in the dark. from 178 to 2ll/trap/day during June through However, it laid eggswithin a few minutes of the 28 JounNer, or t.us AMERTCANMosqurro CovrnoL AssocrrlrroN

Age composition ofadult Diptera may be used = / 0.9152 as an index for estimating longevity and survival Y - -270.74+ 17.65()0 ,/ . of the populations (Detinova 1962). Our obser- vations indicated that >2-day-old adult female 'rso t G. paripes predominated in the field and these F females were ready to reproduce. The life span ft too paripes 6 of adult G. is rather short-from 4 to 6 days (Nielsen 1962). z Although the adult life span of G. paripes is much shorter than most mosquito species, the severe nuisance problem posed by the phenom- enal numbers in which these emerge, swarm, and congregate in urban water fronts ne- Fig.4. R"r"tio"rhi;l'.:T"ii' fi nr,, "nd ip e s p a r i - cessitates implementation of control measures. pes abundanceand air temperaturesat lakefront, Lake The present findings suggest that adult control Monroe, Sanford, FL (June-December 1992). of spring populations is warranted because of their higher reproductive potential. Adulticiding conducted in the evening hours should prevent onset of light in the laboratory. The cause of this gravid females from laying eggs the following difference in observations is unknown. However, morning and thus reduce the development of based on our observations we suggestthat change potential future populations as well as existing in light intensity is a stimulating factor for ovi- ones of this pestiferous midge. position activity ofthis species. The number of egg masses laid by a female REFERENCES CITED chironomid and the number of eggs/mass may vary by species and strains (Branch and Wichita Ali, A. 1980. Diel adult eclosionperiodicity of nui- sancechironomid midges of central Florida. Envi- 1923, Morrow et al. 1968). Female Pseudodi- ron. Entomol. 9:365-370. amesa arctica (Malloch) and, Heterotrissocladius Ali, A. 199I . Perspectiveson managementof pestif- (Kieffer) group subpi losus successfully completed erous Chironomidae (Diptera), an emerging global the development of 2 ovarian cycles without problem.J. Am. Mosq. Control Assoc.7:26G-281. feeding, although neither oviposited (Oliver Ali, A., R.-D. Xue and R. Lobinske. 1993. Efficacy l97l); however, in some midge speciesa2ndegg of two formulations of the growth regulator, batch is produced after deposition of the first pyriproxyfen (Nylaro or Sumilarv@) against nui- batch (Fischer 1969). In our observations, lab- sanceChironomidae (Diptera) in man-made ponds. oratory-reared and field-collected G. paripes laid J. Am. Mosq. Control Assoc.9:302-307. A., M. Mulla, B. A. Federiciand F. W. Pelsue. only a single egg mass. The field-collected fe- Ali, S. 1977. Seasonalchanges in chironomid fauna and males were mostly nulliparous. No traces of a rainfall reducingchironomids in urban flood control second oviposition were observed despite indi- channels.Environ. Entomol. 6:619422. cations of development of some 2nd follicles. Biever,K. D. 1965. A rearingtechniqueforthecol- The selection of water type for oviposition by onization ofchironomid midges.Ann. Entomol. Soc. G. paripes was not previously elucidated (Nielsen Am.58:135-136. 1962). Our observations indicate that G. paripes Branch,H. E. and K. Wichita. 1923. The life history generally may not have an oviposition preference of Chironomus cristatus Fabr. with descriptions of for a certain water type, but the survival and the species.J. NY Entomol. Soc.3l:15-30. Detinova,T. S. 1962. Agegrouping methods in Dip- hatching of eggsmay depend upon the water type, tera of medical importance. W.H.O. Monogt. Ser. quality. essentially water The maximum hatch 47. in the present study was recorded in the lake Fischer,J. 1969. Zur fortpflanzungsbiologievon Cftl- water, which was perhaps chemically more suit- ronomus nuditarsisStr. Rev. SuisseZool. 76:23-55. able for survival and hatching of eggs of G. pari- Lieux, D. B. and J. A. Mulrennan. 1956. Investiga- pes than the other 3 water types tested. tion of the biology and control of midges in Florida Among environmental factors, temperature is (Diptera:Tendipedidae). Mosq. News I 6:20l-204. the most obvious factor that affects seasonal cy- Morrow. J. A., J. L. Bath and L. D. Anderson. 1968. key to eggmasses of some aquatic cles and abundance of chironomids (Ali et al. Descriptions and midges in southern California (Diptera: Chironom- 1977).ln the present study, air temperature had idae).Calif. Vector Views l5:99-108. (r : < a highly significant 0.91, P 0.01) rela- Nielsen, E.^t. 1962. Contributions to the ethology of tionship with the adult populations (Fig. 4). Glyptotendipes (Phytotendipes) paripes Edwards. Oi- Rainfall did not seem to have any influence on kos 13:48-75. the adult populations or on percent parity rates Oliver, D. R. 197l. Life historyoftheChironomidae. in this short-term study (Fig. 3). Annu. Rev. Entomol. 16:211-23O.