STUDIES ON THE BIOLOGT, ECOLOGY, DISTRIBUTION, AND CONTROL OP EPICAERUS AURIFER BOH. (CURCULIONIDAE), A NEW PEST OP ALFALFA IN MEXICO

Dissertation

Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By George Mallory Boush, B. Sc., M. Sc. The Ohio State University 1955

Approved by

Adviser Department of ZoolDepartment Zool and Entomology ACKNOWLEDGEMENTS

The author wishes to express his sincere appreciation to Dr* D# M# DeLong, Department of Zoology and Entomology, The Ohio State University, for his inspirational guidance and counsel in connection with this study and to Drs# Douglas Barnes and John J# McKelvey of The Rockefeller Foundation for their advice and encouragement# Grateful acknowledgement is also made to Mr# Francisco Gonzolez and Miss Carlota Riess H#, Mexican Agricultural Program, for their assistance in preparing the drawings; and to Miss Rose E. Warner, Dr# E# W# Baker, Entomology Research Branch, U.S#D#A., Dra# Helena Brava and Dra# Leonila Vasquez G#, University of Mexico, for determining the species of insects, mites, plants, and mammels res* pectively as referred to in this dissertation; and to Mr# E. L# Sleeper who assisted in the preparation of the section on taxonomy# I should also like to thank The Rockefeller Foundation for making this study possible# Finally, I should like to express my heartfelt gratitude and thanks to my wife, Sara, for her constant help and encouragement#

ii Table of Contents

Page Introduction...... 1

Taxonomy ...... 6

Description of the S t a g e s ...... 8

A d u l t ...... 8 Egg ...... 12 Larva ...... 13 Pupa ...... 15 Life History and Habits ..... 17 Adults ...... 17

Qnergence ...... 17 Sex Ratio ...... 18 Mating ...... 21 Preoviposition Period .... 22 Ovlposltlon .... 23 Number of Eggs and Egg Masses Laid per Female 27 Longevity ..... 28 Description of Damage .... 30 Behavior Studies ...... 31 Eggs «...... 32 Incubation Period .... 32

Egg Development and Hatching...... 36 ill Page Larva ••••••...... 37 Number of Instars ...... •...... 37 Description of Damage . ♦♦♦ 3d

General Habits ...... I4I4.

Pupa ...... I4.6

Host and Food Plants ...... I48 Natural Enemies ...... 53 Predators ...... • 53 Parasites...... 57 Population Dynamics ...... ••••••• ....«» 57 Distribution Studies ..... »••• 60 General Description of the Area Studied ...... 60

Method of Determination ...... 6 7 Control ....*• 78 Cultural ...... 78 Chemical ...... 78 Laboratory ...... 78 F i e l d ...... 80 Summary and Conclusions ...... 89 Appendix .... 93 Literature Cited ...... 100 Autobiography ..... • 102

iv Introduction

The present study concerns the biology, ecology, distribution, and preliminary control studies of the

curculio, Eplcaerus aurlfer Boh*, over a 2-year period in south-central Mexico* Prom the time of the original

description of this insect by Boheman (IQJ4.O) until the present, no work, other than Its inclusion in taxonomic treatises is known. However, three other species of the genus Eplcaerus; E* lmbrlcatus (Say), E. cognatus Sharp, and E* formidolosus Boh. are recognized as pests of agricultural crops. Eplcaerus lmbrlcatus. the imbricated

snout beetle, attacks a wide range of crops In the United States, especially apples, potatoes, and strawberries;

also E* cognatus is a serious pest of potatoes In the highlands of Mexico. The genus is apparently indigenous to the Americas. All of the species recognized by Leng (1920) and Blackwelder (l9i^7) were originally described from the southern portion of the United States, Mexico, and Central America* Although not yet recorded in the literature, E. aurlfer, in the larval stage, is a geographically res­ tricted but highly destructive pest of alfalfa* The adult beetle also attacks the foliage of alfalfa as well as the foliage of corn, soybeans, and field beans* However, the principal damage to alfalfa is by the feeding of the larvae on the primary root of the plant.

1 This tunneling and boring eventually results in the weakening or destruction of the plant. Attacks by this pest on a commercial basis result in a progressive dieback or loss of stand in previously well established alfalfa fields. Usually, heavily infested fields are abandoned or plowed under aa a result of these attacks* Its importance as a potential major pest can be further realised when it is noted that alfalfa, under irrigation, is the most important forage crop grown in Mexico. Alfalfa, as food for cattle, forms the basis for the dairy Industry. Its productivity is high. When properly cared for and under favorable conditions it may remain in production for 5 to 7 years, annually producing as many as 9 or 10 cuttings. In addition, certain areas of Mexico are famous for the production of high quality alfalfa seed* This problem was undertaken largely because of the potential economic importance of this Insect and because of the lack of information concerning its habits, range, and control* Inorder to carry out studies on various aspects of the biology, ecology, distribution, and control of E. aurlfer. the author established a program of field and laboratory experiments. Life history studies, pop­ ulation dynamics, movement studies, biological control, and determination of range and large plot control tests were done in the field* The laboratory studies included all physical measurements as well as determination of the incubation period, longivity, egg-laying habits, food plant preferences, and preliminary laboratory control experiments* As there is no published data concerning the location and size of commercial alfalfa growing regions of Mexico, a program was also undertaken in which the author visited and mapped these areas* To facilitate the studies on the biology and control °? aurlfer it was essential to obtain permission to utilize an area heavily populated with this insect* For insectary work on longevity, egg laying studies, and laboratory insecticide screening, it was necessary to be able to obtain several thousand individuals of approximate known age at a given time. Similar land was needed for field use in biological and insecticidal control studies as well as population studies* La Patera, a dairy farm of approximately 200 acres, located on the northern outskirts of Mexico City, was found to be heavily infested with E. aurlfer* The owner of the farm, Mr* Francisco McCann, was greatly concerned over the possible depredations of this Insect and gener­ ously consented to make available land and labor for experimental purposes. The farm was completely irrigated and planted in corn and alfalfa* k In late April 1952, on the McCann farm, a lj. acre field of 3 year old alfalfa of the variety Oaxaca was found to be particularily heavily infested with E* aurlfer* This field was immediately designated as a biological and population study area and efforts were made to keep it in as undisturbed condition as possible* During the spring and summer of 1 9 5 2 and 1953 this field was obser­ ved and examined twice each week. During the remainder of the year the field was examined at approximately weekly intervals* The progress of the various life stages was largely determined by examination of 10 plants, selected at random, in the above field at regular weekly intervals* The larvae and pupae collected at this time, together with collection data, were placed in vials containing

Peterson* 8 (1914-7) K.A.A.D. solution and later transferred to 80 per cent ethyl alcohol* These specimens were later measured and carefully observed for possible parasites* Samples of plant tissue damaged by this curcullo were also collected at the same time and placed in 8 0 per cent alcohol for more critical observation In the lab­ oratory* Measurement of adult population fluctuations were secured by placing five 1 square meter quadrats, at weekly Intervals, during the rainy season on the alfalfa field designated for biological studies* 5 A similar alfalfa field, located adjacent to the biological studies field, was utilized for control exper­ iments* One portion of this field was used to determine the effects of overgrazing in controlling this pest* An equal portion was used to determine the effects of flooding in controlling E. aurlfer* Also at La Patera, insecticide treatments were applied to the soil of seedling alfalfa on a field basis as well as foliar applications of various insecticides to fields of alfalfa infested with adult curculios* All of the insectary and laboratory tests on E. aurlfer were carried out at the Agricultural Experiment Station at Chapingo located 23 miles southeast of Mexico City at the National School of Agriculture* Adequate greenhouse and insectary facilities were available at Chapingo for these studies* Specimens collected at La Patera were brought to Chapingo for more critical biological studies* Cages were also constructed at Chapingo in the insectary to house various small mammals utilized in natural predator studies* 6 Taxonomy

Eplcaerus aurlfer Boheman (Original Description) Boheman, C.H. l81j.O. Schoriherr Genera et Species, Curculionidium, Vol. VI, Part 2, p. 278. Eplcaerus aurlfer Boheman Sharp, David. 1891. Biologia Centrall- Amerlcana Coleoptera, Curculionidae, Vol. IV, Part 3(1889-1911), P* 119* Eplcaerus aurlfer Boheman Dalla Torre, K. W. von and M. P. van Emden. 1936. Coleopterorum Catalogus

pars ll|.7, p* lf-2 • Eplcaerus aurlfer Boheman Blackwelder, R. E. 19kl* Checklist of the Coleopterous Insects of Mexico, Central America, The West Indies, and South America. U.S. Nat. Mus. Bui. 165, Part 5, p* 797* In Sharp (1891) and Blackwelder (19lj.7)f Eplcaerus ravldus Is synonomized with E. aur1fer.Sharp admits that he created this synonomy without making an exact comparison of the types of these two species. He further Indicated that E. ravldus would prove to be a thickly-scaled and finely-punctured fcrm of E. aurlfer. 7 If these two species are synonomous, this species must take the name E* ravldus as this species was des­ cribed on the page preceding E* aurlfer in the same publication* Until the types of these two species can be crit­ ically examined by a person familiar with the variabi­ lity in the genus Eplcaerus. it would be less confusing to consider these two forms as distinct species* It would seem preferable to retain the name aurlfer In the litera­ ture as It Is the name under which it has been recognized for over $0 years* 8 Description of the Stages

Adult The adult beetle Id robust and more or leas cylin- drical in form (Figure 1)# The antennae are scaly, strongly elbowed, inserted at the sides of the beak in deep ant-

ennal groves, and 1 1 -segmented# The last 3 segments of the antennae form a compact annulated club# The mouth- parts are well developed# The paired mandibles are short, stout, and pincer-llke, possessing a characteristic conical depression resembling a scar on their outer surfaces# The beak is short and stout although longer than the head, not constricted between the eyes, slightly dilated and strongly notched at the tip# The prothorax is highly arched with the apex truncate. The elytra with lij. to 1 6 rows of indistinct punctures are fused and completely cover the abdomen when viewed from above. The inner wings are rudimentary and the metanotum memb­ ranous# The front coxae are contiguous, the middle and hind coxae are slightly separated# The third segment of the tarsi is wider than the second and deeply bilobed# Depending largely upon age, the body may or may not be densely covered with fine silvery-gray scales# The adults range from ash-gray to black in color# The sexes in some cases may be difficult to differ** entlate without disturbing the genitalia* Usually, how­ ever, in lateral profile the abrupt angle formed at the apex of the elytra in the female is considerably unlike the evenly rounded angle formed at the apex of the elytra in the male* Also, as seen dorsally, the distal portion of the head of the female is usually greater than half the width of the thorax, whereas the head of the male is usually less than half the width of the thorax* In general, the females are larger than the males. A summary of the measurements of lengths and widths of 200 males and 200 females are given in Table I* Measurements of width was taken across the widest portion of the elytra, and of length as the distance from the apex of the snout to the apex of the abdomen* 10

Table I Summary of measurements of adults; aurlfer. June 1952, Chapingo, Mexico*

Number Length (Mm.) Width (Mm.) Sex Measured Minimum Maximum Mean Min* lltax. kean

Male 200 6.9 12.0 10.2 2.5 k>9 3*9

Female 200 8.2 llj.,5 11*7 3*0 6.0 11

Epicrerus hurifer Bqh

Figure 1 .- Dorsal and lateral aspects of the adult stage of E* aurlfer* The eggs are ovoid in shape, slightly tapering toward the ends (Figure 2-A). When first deposited the eggs are opaque but later tend to gradually become translucent as the incubation period increases. Just prior to hatching the dark head capsule of the embryo can be clearly seen within the chorion. The chorion is not superficially marked in any way.

Measurements of 93 ®ggs» within I4.8 hours following deposition, were made with a dissecting microscope and an ocular micrometer. The results of these measurements are summarized in Table II.

Tabid II Summary of measurements of eggs of EU aurlfer. July 1952, Chapingo, Mexico

Number Length (Mm.) Width (Mm.) Measured Minimum Maximum Mean Minimum Maximum Mean Color

93 1.20 I.I4.6 1 .314. 0.20 O.I4.6 0.32 White 13

Larva

The fully developed fourth instar larva is cres­ cent-shaped or cyphosomatic (figure 2-B). The body is fleshy, near-white to cream in color, and composed of

13 segments, each showing 2 plicae on the dorsal surface. All segments with the exception of the posterior 3 or 1^. are equal or nearly equal in size. The larvae are leg­ less; however, the 3 thoracic segments are distinctly knobbed. The ventral portion of the body bears Ij. to 8 indistinct setae per segment. The abdominal spiracles, shown in detail in Figure 2-B, are 9 in number and are found one per segment per side. They are of the annular biforous type.

The head is distinct, usually exposed and varies in color from cream in the newly hatched first instar larva to dark brown in the fully developed fourth instar larva. The mouthparts are hypognathous, and fitted with paired heavily sclerotized mandibles. Antennae are present, but small and indistinct; ocelli are absent. A summary of the measurements of the larval stages are shown in Table III. It was also from this table that the number of larval instars of this insect was calcu­ lated. Table III Summary of measurements, in millimeters, of larvae; Eplcaerus aurlfer. May 1953» Chapingo, Mexico*

Number Wdth. Head £ap~ Lth. of Body Wdth. of Body Inatar Measured Min. Max. Mean Min* Max. Mean Min. Max. Mean

1 * 38 0*28 0 .3 6 0.33 i.ia 1.59 1.5 2 0 .3 8 0 .5 9 0.1+7

2 . 63 0.51+ 0 .8 0 0.65 3*28 5 .2 6 1+.32 0.68 1.1+2 1.02

3. 39 1 .0 3 1.77 1.33 1+.33 3.98 U .6 7 i.ia 1.91 1*67

k. 36 2.10 2 .8 1 2 *14-6 8.9 11.1+ 10.3 2 .2 1+.6 3.1+ 15

Pupa As the pupal period approaches, the larva, In the prepupal stage, shortens and becomes barrel-shaped* The rather Indistinct segments become deep and well defined* The head at this time Is deeply retracted Into the body* The actual metamorphosis from larva to pupa has not been observed* The pupa (Figure 2-C and D) is of the exarfite type; that is, possessing free appendages* The spiracles occur as prominent knobs and might possibly serve as taxonomic characters* Fourteen pupae were measured and found to have an average length and width of 7*2 Mm* and 2*9 Mm* respectively* The minimum width and length recorded were 2*6 Mm* and 6*9 Mm*, and the maximum length and width were 7*6 Mm* and 3*2 Mm* respectively* The pupa is light brown in color* 16 Ep ie h e r u s h u r if e r Bdh

Figure 2.- A, egg stage* B, lateral view of larva* C, and D, ventral and lateral view of pupa* 17

Life History and Habits Adults Emergence Three alfalfa fields, heavily damaged by the at­ tacks of E*. aurlfer. were observed over a period of two seasons to determine the time of emergence of this pest* The fields were located at La Patera dairy and Chapingo, Mexico, as located previously, and Chaleo, Mexico* Chaleo is located 30 miles south of Mexico City* All three fields were in the Mesa Central region of Mexico and shared approximately the same altitude and climatic conditions. Emergence of E* aurlfer in both 1952 and 1953» at the three areas under observation, always occured within 2 l+ hours following a series of early spring heavy rains* The newly emerged individuals, covered with mud, were usually found within the crown of the alfalfa plant, head down and half covered with dirt and debris* The sexes at this time were approximately equal* Caged males and females refused to copulate or eat for a period of 2 to 1+ days following emergence. Also, for two or three days after emergence the insects frequently defecated a semi-solid substance* The results of the observations on time of emer­ gence are given in Table TV. 18

Table IV Dates of emergence of E. aurlfer in 1952 and 1953*

Year La Patera. P.F. Chaleo. Mex. Chapingo. Mex»

1952 May 27 June 8 June 7 1953 June 7 June 11 June 11

Sex Ratio The sex ratio of E. aurlfer varies with time as there exists a definite difference between the longe­ vity of the males and females. Observations on sex ratio would therefore largely depend upon the age of the sample studied. In this study, sex ratio was determined by field collected beetles, In which a 2 5 square meter quadrat, replicated ij. times was utilized. Collections were made at La Patera at I4. periodic times during the season. As shown in Table V, the sex ratio at the beginning of the summer was almost 1:1. As the summer progressed, the ratio of males to females decreased, eventually reaching a ratio of nearly 1 :3 * 19

Table V Sex ratios of EU aurlfer at periodic Intervals during the 1953 season* La Patera, D* P*

Number Per cent Per cent Approx* Dates Collected Male______Female______Sex Ratio June 15 2,530 lj.6.7 53*3 1:1 July 12 1,809 37*8 62.2 1:1*5 Aug. 9 l,3Ui|- 32.9 67.1 1:2 Sept. 6 236 27.0 73*0 1:2.3 20

Figure 3*- Potted alfalfa and cellulose acetate cages utilized in the biological studies conducted in the greenhouse.

■ 21

Mating A series of cages (Figure 3), constructed of cel­ lulose acetate In the form of hollow cylinders 10 inches In diameter and 22 inches high was used to observe the mating habits of E. aurlfer* Muslin was sealed over one end of the cages with acetone, and two 3 inch round windows cut in the sides of the cages and sealed with fine copper wire were provided for ventilation. Each cage was placed over a 12 inch flower pot containing a single 2 year old alfalfa plant of the variety Oaxaca. A newly emerged male and female were placed in each of the ij.2 cages used in these observations. Mating did not usually take place until 3 or ij. days after emergence and occured on the ground as well as on the stems of the plant. Copulation occurs as fol­ lows: the male approaches the female from the side or rear, and if not prevented by movements of the female, mounts from the rear. If she is receptive and does not flee, he clasps her elytra with first his front and middle legs and finally with all three pairs of legs. The aedeagus, which is sheath-like, is then inserted in the fully extended ovipositor. During the lengthy copulation, little movement on the part of the male takes place, although the female may walk about and frequently feeds. 22

The time for 35 matings ranged from 16 minutes to 31 hours; the average being 3^ hours* Mating usually occured at night, early morning and on overcast days# In 9 cages containing 3 marked males and 1 female, all the males were observed to mate with the female within 72 hours* Of the caged pairs, copulation took place an average of 3 times during the 3 month duration of the observations. Although egg production reached its peak during early July and fell off rapidly thereafter, mating continued until early fall* In a separate series of 21 cages utilizing a sin­ gle newly emerged female in each cage, no eggs were deposited. Apparently mating is necessary for egg pro­ duction# It Is not known if frequent copulation Is necessary in the field for maximum egg production. Possibly the frequency of copulation in the greenhouse was due to caged conditions or environmental factors different from those found in the field# The mating observations in the greenhouse occured at temperatures ranging from 6l to 88 degrees Fahren­ heit# Preovlposltlon Period The preoviposition period of the female varies from 3 to 7 days# In a series of I4.2 cages, as described 23 under the prior topic, in which 1l 2 newly emerged females were allowed to mate once, the average preoviposition period for 31 females which produced eggs was 3.9 days. Of the 11 unaccounted for Individuals, Ij. died prior to egg deposition and 7 deposited no eggs.

Observations at La Patera in the biological study field were in accord with the laboratory results.

Although densely populated with newly emerged adults, no egg masses were found within a week of emergence of the first individuals.

Dissection of newly emerged unmated females re­ vealed rudimentary ovaries with no visible eggs, to­ gether with a large mass of fatty tissue. Further dissection of females which had been allowed to mate

2 days prior to the observations showed a decrease in the fatty tissue and the partial development of recognizable eggs.

Oviposltlon

The eggs are deposited in ovoid or linear groups

(Figure 2-A) on the top half of the host plant. There are two methods of deposition: the eggs are deposited in the fold of a single leaf or leaflet (Figure i^.); or they are deposited between two opposing leaves or leaflets. A sticky, fast-drying substance secreted by accessory glands located near the ovipositor aids 2 k

in anchoring the eggs to the surface of the leaf, or substrate, as well as sticking the edges of the leaves together* Oviposition usually occurs at night or in early morning. The females are easily disturbed at this time and feign death readily. Six apparently complete acts of oviposition were observed. They varied in duration from approximately 20 to 36 minutes, averaging 25 minutes* Temperatures during the observations ranged from 6I4. to 79 degrees Fahrenheit* A female in the process of egg deposition is shown in Figure 1|* Prior to oviposition, the female walks rapidly up and down the stem of the plant, oc­ casionally examining a leaf with her antennae and front legs* When a suitable site is found, the leaflet or leaves are pulled or bent into position by the legs to form a trench-like depression* The actual egg laying act occurs with the head of the female directed away from the plant* The ovipositor is tele­ scopic in action and when fully extended is about half the length of the elytra. The under surface of the leaf is usually preferred for oviposition and the eggs are deposited from the distal part of the leaf Inward, in a single layer usually in a ovoid mass but occasionally in a straight line* 25

Of 368 egg masses collected at La Patera June 21, 1952, 59 per cent were formed by the folding over of a single leaflet and 1(1 per cent by the union of two leaflets* Figure I4.#- Adult female beetle ovipositing on alfalfa 27

Numb or of Eggs and Egg Masses Laid per Female A series of tests were conducted in June and July, 1952 and 195*3 at Chapingo to determine the number of eggs and egg masses laid per female* A similar series of Ij.2 caged alfalfa plants, as described previously under Oviposition. were used during both years in these observations, A newly emerged male and female curculio were introduced in each cage. The newly produced egg masses were tagged daily. Temperatures in the green­ house during the tests ranged from 66 to 89 degrees Fahrenheit, Of the 82 caged pairs, 53 females deposited from 1 to 7 egg masses, averaging 2,17 egg masses, each containing from 9 to 55 eggs with the average being 2lj.,6 eggs per mass. The remaining 29 females died prior to egg deposition. Field collections and observations at La Patera during June 1952 on 202+. egg masses showed a range of from ij. to lj.9 eggs per mass, with the average being 25*7 eggs per mass. More than 75 per cent of the egg masses in the laboratory tests were deposited from June 15 through July 15, However, egg production remained light and sporadic into the middle of September, In the field, the egg masses have been collected 28

from J4. plants, alfalfa, corn, beans, and Amarantus

S£. In the laboratory, in 6 caged flats containing alfalfa, corn, beans, wheat, and Irish potatoes, egg masses were deposited on alfalfa, corn, and wheat. However, only 1 egg mass containing 7 eggs was found on wheat and 2 egg masses containing 12 and 18 eggs respectively was found on corn, whereas, 21 egg masses were found on the alfalfa plants. Each flat contained 10 pairs of newly emerged beetles*

Longevity In the laboratory tests conducted at Chaplngo on preoviposition and oviposition observations as well as the determination of the number of eggs laid per female; studies, utilizing the same caged paired adults were carried out to determine longevity* These obser­ vations were apparently of little value as the longev­ ity of the adults caged in the laboratory wasnearly one month less than the longevity of similar beetles caged in the field. The laboratory tests were aban­ doned on August 20, 1952 and on August 17# 1953 because of the death of the beetles* The longevity of this species, as an adult population in the field, during 1952 and 1953 Is given in Table VI* 29

Table VI

Presence of adults of E., aurlfer at 3 locations In Mexico during 1 952 and 1953*

Plrst Last Presence First tast Presence Location Obs, Obs* / (Days) Obs* Obs* (Days)

Chapingo, 6/7 10/2 1 2 5 6 /11 1 0/6 117 Mexico Chaleo, 6/8 1 0/2 126 6 /11 10/7 118 Mexico L a Patera, 5 / 2 7 9 / 2 9 126 6 / 7 10/3 118 D. F. 30

Description of Damage Alfalfa Is thought to be the only cultivated crop seriously Injured by E* aurlfer* Injury Is primarily the result of the feeding of the larvae on the primary root, however, the adults also damage alfalfa by feeding upon the foliage (Figures 5 and 6)* Although probably of little economic significance, the adult has also been observed, by the author, feeding occasionally on other cultivated crops* These crops are Its follows: 1.- C o m - Zea mays L* 2.- Beans- Phaseolus vulgaris L* 3*- Soybeans- Sola max L. ij.*- Wheat- Trltleum sativum L* The foliar damage to these crops as a result of the feeding action of the adult beetles may be described as a general scalloping of the leaf margins and occasionally the severing of a leaf or leaflet from the petiole* Feeding may occur over the entire plant but usually it is restricted to the young tender growing portions* In alfalfa, this damage is partic­ ularly important as the new shoots in the crown of the plant, representing the new growth, are frequently seriously damaged or destroyed. 31

Behavior Studies Probably the most obvious biological observation concerning the adults is that they are negatively phototropic. Eating, mating, oviposition, and movement from one location to another usually take place at night or under subdued light conditions. The adults have been repeatedly stimulated into activity in the greenhouse during the day by darkening the cages in which they were located. Generally from 9 to 10 A.M., until 5 or 6 P.M., C.S.T., the adults are inactive and are found under loose litter, debris or dirt. Often, the head and thorax are buried in the soil or debris and the entire abdomen is exposed. During periods of activity the adults are easily disturbed and "feign death". At such time the legs are doubled up under the body and the insect may remain immobile for 10 or 1$ minutes. They may usually be revived by placing the beetle in the palm of the hand and gently blowing upon it. Eplcaerus aurlfer was rarely collected singly in the field. Usually, when located, they are in or near alfal­ fa and present in great numbers. They do not appear to be gregarious but are found locally in large numbers probably because of adequate food and suitable environ­ ment. 32

Eggs Incubation Period

A total of 63 egg masses, deposited on alfalfa of the variety Oaxaca, were tagged within 2i+. hours of deposition and observed at daily intervals. The tempera­ tures in the greenhouse during the duration of the obser­ vations ranged from 66 to 89 degrees Fahrenheit* The incubation period varied from 27 to 3^ days* The results of these observations are shown in Table VII. 33

Table VII

Incubation period of egg masses of B* aurlfer. Chapingo, Mexico, 1952*

Incubation Number Period Masses Per cent (days)______Hatched______Hatched 26 0 0 27 2 3.2 28 k 6.k 29 Ik 22.2 30 20 31.7 31 11 1 7 4 32 9 H4-.3 33 2 3.2 3k 1 1.6 35 0 0 Total 63 100 311-

Figure 5*- Alfalfa leaves showing characteristic feeding damage by the adult stage* 35

Figure 6«« Alfalfa plant showing the results of adult feeding (Note characteristic crown injury)* Egg Development and Hatching

When first deposited and during the first week of

incubation, the eggs are opaque and pearly white. During

the second and third week they appear grey; and during

the last 8 to 10 days are translucent and almost color­ less. During this later period, the head capsule of the embryo can be seen within the chorion.

Observations were made at the time of hatching on

3 egg masses. The larvae utilize their mandibles in rupturing the membraneous chorion and escape from the end of the egg. The actual time elapsing from the initial rupturing of the chorion until the larva clears itself of the egg ranges from 2 to 6 minutes, averaging approx­ imately 3 minutes. The majority of the individuals of a given egg mass hatch at the same time. One egg mass containing 18 eggs hatched in 28 minutes; another containing 1+3 eggs required 72 minutes for 1+0 of the eggs to hatch. A third egg mass, containing 12 eggs, required 125 minutes for complete hatching. Eighty-four egg masses were collected July 6 , 1 9 5 3 from the biological study field at La Patera and brought to Chapingo for observation. The egg masses, each in a single petrl dish, were placed in a constant temperature cabinet controlled at 70 to 72 degrees P. and 70 to 80 37

percent relative humidity. Only 12 individuals, from a total of 2187 eggs, hatched. Possibly the living leaf forms an

environmental microclimate, difficult to measure and du­

plicate, which is essential for successful incubation. This latter possibility might form the basis for some form of culturally controlling E. aurifer.

Also, the long incubation period required, and the

vulnerability of the egg masses on the upper portion of the

plant might be considered a weak link in the life cycle of this pest.

Larva Number of Instars

Since the larvae go into the ground immediately upon hatching and undergo all of the growth stages there, it was not feasible to observe a series of individual larvae to determine the number of instars and the time elapsed in each

stage. Also attempts to collect larval cast skins and head capsules by screening and flooding the soil were unsuccess­ ful.

To determine the number of instars as well as other biological data, a regular weekly collecting system was established. Prom mid-April, 1952, until December, 1953» a collecting trip was made each Saturday to the biological study field at La Patera, Ten alfalfa plants were dug each 38 week and examined, along with the associated soil for lar­ vae. The larvae, together with the collection data and the number of larvae per plant, were placed in K.A.A.D. solution for examination in the laboratory.

From these field collections it was determined that E, aurlfer has one complete generation per year. No full grown larvae or pupae were found in the soil from the middle of June through August. Measurements of the width of the head capsule of 176 larvae, as well as length and width of the body, from the above collections at La Patera are given in table 3* The head capsule widths separate into 1+ fairly well defined groups.

To determine if an ecdysis had been overlooked, the principle, as proposed by Dyar (1890), that the widths of the head of a larva in its successive instars follow a regular geomet­ ric progression in their increase, was applied. The average widths of the head of successive larval instars was as follows: 0.33; 0 .65; 1*33 and 2.i|6 mm. The ratio of increase was found to be .5U« Applying this ratio to the measured widths, the following calculated widths were obtained: 0 . 35; 0 .72; 1.33; and 2.1(.6mm. On this basis it is thought that the larva complete l± instars. Descrlption of the Damage Alfalfa is the only plant that the larvae have been found near or collected from in the field or laboratory. The 39 damage caused by the attacks of the larvae on the roots of the plant are usually brought to attention by the obvious progressive dleback and loss of stand in well established alfalfa fields, (Figures 7 and 8 ). On examination of a given plant, the primary root is seen to be severely injured

(Figures 9 and 1 0 ), b^ the excavations and tunnels caused by the feeding of the larva of E.aurlfer. In general the tun nels are directed toward the central portion of the root.

The principal damage to the plant appears to be by the de­ cay of the entire central portion of the root, apparently caused by the entrance of soil fungi and micro-organisms, (F gure 10).

This decay is rapid and takes place from late summer through the winter to early spring. Loss of stand, as a result of the death of the plants, occurs largely in the winter and early spring. In a badly infested 3-year-old field of alfalfa of the variety Kenya at La Patera in April, 1952, a count of i+OO alfalfa plants, collected by following a ll^-inch plow, disclosed that 96 per cent of the primary roots were in­ jured. As a result of this damage, the field was taken out of cultivation and replanted in com. Although a high population of larvae remained in the soil, the seedling c o m was not injured. Figure 7*- Normal three year old alfalfa field (Variety (Variety field alfalfa old year three Normal 7*- Figure

: Oaxaca)* 1*0 U i

Figure 8*- Three year old alfalfa field (Variety Oaxaca) showing results of attack by the larvae* Figure 9«~ Alfalfa plants showing damage caused by the tunneling and feeding In the primary root by the larval stage* o

c. Figure 10#- Cross section of primary root of alfalfa# A, Injury to central portion of root# B, Healthy root C , Injured root showing entrance hole# hk

General Habits

The larva, in all stages, is subterranean. As the newly emerged forms make their way out of the egg, they

Immediately fall to the ground. By alternately contract­ ing and expanding they rapidly move into the soil at the base of the plant. Observations have shown that newly- emerged larvae perish within an hour or two if the soil is especially dry and hard.

No observations have been made on the feeding habits of the first instar forms. Studies after the newly-emerged larvae enter the soil are difficult because of their minute size and fragility.

Observations on potted alfalfa inoculated with known age larvae, in the greenhouse at Chapingo, have indicated that the larvae pass through the first instar within 10 to lij. days.

The second instar larvae have been observed feeding on the primary root. Usually they appear unable to penetrate the tough central portion of the root and confine their feed­ ing to the soft fleshy epidermal and cortex regions. The time required for completion of the second instar in the laboratory varied from 3 to 7 weeks. The third and fourth instar larvae are found in about equal numbers throughout the fall and winter. In early

April more than 80 per cent of the larvae are In the fourth h5 lnstar.

Feeding continues through the fall and winter. The third and fourth instar forms are responsible for most of the damage to the primary root. Feeding on the root occurs from ground surface level to as deep as 53 inches. Most of the root damage to 3-ysar-old alfalfa occurs from a depth of 2 or 3 inches to about 16 inches.

In the weekly observations of infested plants at

Chapingo during 1952 and 1953 » f©w larvae were actually recovered from the root proper. Usually the larvae were found within 1 to 2 inches of the root. From the almost haphazard riddling of the root, and the few individuals pre­ sent, it would seem that the larvae move frequently, in the soil, up and down the shaft of the l*oot, repeatedly feeding and retiring to the adjacent soil. Damage to the secondary roots by the larvae may occur, but has not been shown to take place. In the greenhouse the larvae appear to be sensitive to varying degrees of moisture in the soil. When water Is withheld from the plants preparatory to sifting the soil for larval recovery, the insects are usually at the very bottom of the pot where the soil moisture is greatest.

When observations were made following a daily watering fcoutlne, the larvae were found at all levels in the soil.

In the field, from 1 to 3h individuals have been re- covered from the soil around a single plant. Although diffi­ cult to form an average, usually 2 or 3 larvae are found per plant.

Pu£a

The pupa is subterranean. It is found in an ovoid earthen cavity located at a depth of from ^ to 1). Inches below the surface of the ground. Usually, the pupal cavity is within Ij. or 5 inches of the root and is often found with­ in the spreading basal crown of the plant.

The pupa when first transformed is near white but gradually becomes light brown, and just prior to emergence takes on a definite grey color.

Although a few (less than 1 per cent) individuals pass the late fall and winter in the pupal stage, most transform from prepupae to pupae about the end of April. The pupal- stage lasts approximately 1 month. The life cycle of E. aurlfer is given in diagrammatic form In Figure 11. The graphs are not quantitatively acc­ urate, but indicate the trend in population size. & £ ■—

(Mi

Ssm.

i.—

& s l . —

VMM

Figure 11 Host and Food Plants

In this discussion, host plant Is limited to those plants, In the field, on which the female deposits eggs and on which larval development takes place. As such, E. aurlfer is known to have but one host plant, Hairy Peruvian Alfalfa, Medlcago satlva L, In this study, Food Plant refers to those plants which serve as a source of food. Eggs may be deposited upon a food plant and not alter its status if larval development does not take place. In addition to the cultivated food plants of this beetle given on page 30, the following wild plants have been recorded as serving as food for the adults.

1 .- Solanum rostraturn L. 2»- Anoda hastata Cav.

3 .- Eruca satlva Lam.

]+.- Rumex obtuslfollus L.

5.- Malva parvlflora L. 6 .- Paspalum sp.

7.- Abutllon sp.

8 .- Cucumls sp.

9*- Amarantus sp .

The latter plant, Amarantus sp.. of the pigweed group, serves as an excellent food plant and is usually devoured when occurring on the margins of a heavily infested alfalfa field. Egg masses have been collected from this plant but apparently the larvae cannot develop upon it as they have never been found in the soil associated with the roots. Larval development would further be curtailed as this plant is an annual and dies in late summer, about the time the lar­ vae would be half developed. Because of the possible deleterious effects of this species on other cultivated crops, an effort was made to determine the relative food plant preferences of selected cultivated crops by the adult beetles. Four cages, con­ structed of screen wire and one meter square in size, were placed in the field at Chapingo June 20, 1952. The ground

surface area in each cage was divided into 6 equal portions, and into these portions were introduced potted com, wheat, beans, alfalfa, potatoes and tomatoes. The corn, wheat and beans were 3 weeks old and the alfalfa was of 2 -year-old transplanted stock. The potatoes and tomatoes were of unknown age but were approximately 8 to 10 inches high. One hundred adult beetles collected from the biological study area at La Patera were introduced into each cage. Observations wero made 2 lj., lj.8 , and 72 hours following introduction of the beetles and the individual crops visually rated as to the degree of injury caused by feeding. The results of these 50 observations are given in Table VIII. The adults seemed to prefer, in descending order of preference; beans, com, alfalfa, tomatoes, wheat and potatoes. 51

Table VIII Pood plant preference teat utilizing selected cultl- vated plants* Chapingo, Mexico, July 1952*

a e .

Corn :Rocomex 1 3 3 : 3 e• 3 3 e • Wheat : -••• 2 2 : 1 ae 1 1.5 e • Beans :Gto«10-A-5 k 3 : 1+ 2 3 3.5 2 e Alfalfa :Oaxaca 2 3 : 3 2 2 2.5 2 • Potatoes :Alpha 1 2 : 2 • 1 1.5 • • Tomatoes :Rutgers 2 2 : 2 • 2 2 •# (< e• • Rating Scale 1«- No feeding 3*»- Moderate feeding 2*- Light feeding lj.*- Heavy feeding Figure 12*- A general view of the countryside in the Mesa Central Region of Mexico* 53

Natural Enemies

Predators Soon after the adult beetles were first seen in the

field in the early summer of 1 9 5 2 , it became apparent that natural enemies were probably the most important single factor in the reduction of the adult population. On June 7, in the biological study area at La Patera, an average of l±2 live beetles were recorded per square meter. Prom this

date through June 2 1 , the number of live beetles per

square meter had been reduced, by natural enemies, to 2 7 * An accurate index as to the efficiency of these enemies could be determined by a count of the hard empty elytra left upon the ground following the apparent eviseration of the beetles. Peces, of a size and shape similar to those of a housecat, were frequently found associated with the remains. When these feces were placed in alcohol and ex­ amined with a dissecting microscope, they were found to be composed almost entirely of cuticle fragments of E. aurifer. From this evidence it was thought that the enemies func­ tioned as predators. Similar eviserated adults and asso­ ciated feces were also seen at Chaleo and Chapingo. At the latter location, an insecticide test against the adults had to be abandoned on July 1 6, 1953> because of the reduc- 51+

tion in beetles by this means. To determine the predator or predators involved, a bounty was offered to the field laborers at Chapingo for the capture of any small mammals native to the area. A total of 12 specimens representing 5 species were procured in this way. The mammals, with the exception of a shrew, were placed in wire cages in the insectary and not fed for 2i| hours following their capture. The feces ex­ creted by each of the animals during this time were examined and compared with the feces containing the portions of E. aurlfer collected in the field. The following day, food

(-I cup of dry shelled com), water and 100 live beetles were introduced into each cage. In these studies, 3 pocket gophers, Cratogeomys merriami merriaml; a small spotted skunk, Spllogale sp.; a large striped skunk, Mephitis sp.; 6 ground squirrels, Cltellus mexlcanus mexlcanus; and a shrew, Sorex saussurel saussurel Merriam, were observed. All of the above species, with the exception of the pocket gopher, eviserated some of the beetles. Both species of skunks ate the 100 beetles introduced into their respect­ ive cages within ij. hours and produced feces, as well as eviserated curculios similar to those found in the field.

Also, 5 of the 6 ground squirrels eviserated and ate from 55

6 to 28 beetles within a i^-hour period following their introduction into the cages. Afterwards, possibly because of the presence of the com, the ground squirrels refused to molest the beetles when they were Introduced into the cages. The skunks, however, refused to eat the corn and re­ peatedly devoured the beetles soon after they were placed in the cage. The pocket gophers were found to be vegetarians and did not eat any of the beetles. These mammals are frequent­ ly found in alfalfa fields where they are considered a pest because of their mounds and tunnels; however, they apparent­ ly eat little but the stems and leaves of plants.

The shrew died, probably of starvation, about i^8 hours after it was captured. Within this time it eviserated ij.8 beetles. The dead beetles were unlike those found in the field in that the eviseration in this case was accomplished by partially separating the ventral cuticular surface of the abdomen from the elytra, rather than the destruction of the entire curculio except the elytra. The feces produced by the ground squirrel and shrew are unlike in size, shape, consistency or color, the feces associated with the effects of the predators in the field. Unfortunately, these observations were limited to laboratory conditions and do not necessarily reflect the actions of these mammals in nafeure. However, as a result 56 of these observations, showing the close similarity between the feces and eviserated beetles found in the field and those produced in the laboratory, the two species of skunks are thought to be predators of E. aurifer* 57

Parasites During the summers of 1952 and 1953 at Chapingo, mites, attached to the ventral membraneous areas of the neck of E. aurlfer were frequently observed and collected. Speci­ mens sent to Dr. E. W. Baker, Entomology Research Branch, were identified as belonging to the family Parasitidae. More exact determination could not be made. Individual curculios with attached mites were placed alive in cages with food so that they might be observed. The beetles did not appear to be inconvenienced by the mites. Copulation, oviposition and feeding proceeded at an app­ arently noimal rate.

Population Dynamics To determine properly the dynamics of a population of a given animal in the field during a known period of time would involve simultaneous sampling at periodic in­ tervals, in replicated representative areas throughout the range of the animal. Such a study would require con­ siderable time, money, and transportation facilities. As these items were at a minimum, It was decided, in the spring of 1952, to conduct a series of observations in a single field known to contain an initial high adult pop­ ulation. The biological study area at La Patera was chosen 58 for this study because of its proximity to the office and the abundance of beetles present. The results of these observations are summarized in Figure 13• The beetles were first seen in the field on May 27, and reached their greatest numbers about 9 days later. The steady decline in population between June 7 and July

5 was thought to be almost entirely due to the feeding action of predators. The subsequent decline in population was probably a result of natural mortality, particularly of the males, as well as predators. The beetles were last observed in the field September 27. A similar study was undertaken at the beginning of the 1953 season, but for reasons unknown to the author, the population of B. aurlfer had diminished to a level so low that it was not possible to measure the fluctuations during the season. 59

'R c m r/L 'E /Y i/m z R su f z u r c u u o s f f r F Q F

ffitf 1 - S U CFFCl/UFS/l Stf M

rcs i* !* ‘J? A 221 _i*L I**£ H A !•* JL id^

-.=V- •j^y

--_r? ------V-"-_ \ /w | - A t/l

/ s'/c^

§ s \ A ./ |§-tf A/-? *< K ______s /Jo g % /

- . _ r? / A < £ Y

— .2. ______Sj'S-t'X d / //-? ^ / •s SH-- \ ^ 30 / / A ^ / lq--« l t8 . L w ! i**X Figure 13*- Adult population changes of S* aurlfer in a alfalfa field in Central Mexico in 1952* 60

Distribution Studies

General Description of the Area Studied The biological and control studies of L. aurifer were carried out in the states of Mexico and Distrito Fed­ eral. (For reference purposes, a map with the states of the Republic of Mexico, is shown in Figure l[|J. These two states form a portion of a high, semi-arid plateau region, gen­ erally referred to as the Mesa Central geographic zone (Wellhausen 1951)• This zone, as shown in Figure 15, varies

in altitude from about 6500 to 8500 feet and has a definite dry and rainy season. The climate is generally temperate throughout the year. Because of the mountainous nature of south-central Mexico, with the resulting high number of ecological niches and microclimates, the area is extremely difficult to classify. Leavenworth (1931) in his classification of ffuevo Leon points out that "classification based solely on precipitation, temperature and evaporation data can never be satisfactory for ecological purposes in mountainous areas because (l.) data is often Insufficient or lacking

and (2 .) the relationship between climate and biological phenomena does not lend itself to mathematical formulae." Possibly a better index of the climate and soil of a given region can be gained by an analysis of the vegetation. 61

Leopold (1950) prepared a map of the vegetatlonal zones of Mexico, giving what he considered the original climax vegetatlonal types. This map is shown in Figure 1 6. A photograph, showing a typical view of the general terrain in the Mesa Central is given in Figure 12. At present, the principal cultivated crops in this region are corn, beans, wheat, vegetable crops and alfalfa. Generally speaking, it Is probably the most productive agricultural region In Mexico. Although probably of limited use in field biological studies, official meteorological data from the municipality nearest the various study areas, expressed in the form of climographs, is presented in the Appendix. The climographs were thought to be helpful in the comparison of progressive seasonal precipitation and temperature of one area with that of another area. The climographs are of the type used and described by Munns (1922) and Transeau (1935)* The tempera­ ture and precipitation data presented In the climographs are from a 5-year summary of weather conditions In Mexico published by Contreras Arias (19U2). 62

Figure ill*- Map of the Rebubllc of Mexico showing the state boundaries* SONORA

CHIHUAHUA

COAHUILA

SINALOA N. LEON

DURANGO

ZACATECAS

\ S. LUIS POTOSi" AGS. YUCATAN

GTO. HIDALGO- JALISCO

J J MEXICO ;t l a . MICHOACAN pf- CAMPECHE COL. MOR; puEBLA TABASCO VERACRUZ

GUERRERO

OAXACA CHIAPAS 6 k

Figure 15*- Map of the Republic of Mexico showing the general geographic regions (Wellhausen)• 6 $

Figure l6*« Map of the Republic of Mexico showing the major vegetatlonal regions* TEMPERATE BOREAL FOREST PiNE-OAK FOREST CHAPARRAL mesquite-grassland I j OESERT

TROPICAL CLOUD FOREST RAIN FOREST TROPICAL EVERGREEN FOREST C«5l SAVANNAH TROPICAL DECIDUOUS FOREST |===1 THORN FOREST ARID TROPICAL SCRUB

MEXICO VEGETATION MAP

MUSEUM O f VCfttCWUTC 2QCL0CT

vwe«*rr cvcaufornm

BY A S. LEOPOLO 67

Method of Determination Two methods were used to determine the present dis­ tribution of E. aurlfer» The first method employed con­ sisted of numerous field collections of the beetles in a progressively wider circle from the point of known occurence; and the second consisted of requesting avail­ able collection data for this species from the larger museums. The following museums cooperated in this respect, 1,- U. S. National Museum, Washington, D. C. 2,- British Museum (Natural History), London, England 3,- American Museum of Natural History, New York, N. Y,

14.,- Zoology Museum, University of Texas, Austin, Texas 5>»- Entomology Museum, Cornell University, Ithaca, N, Y, 6,- Snow Museum, University of Kansas, Lawrence, Kansas 7,- Museum, Illinois Natural History Survey, Urbana, 111. 8,- Entomology Museum, Ohio State University, Columbus, 0. 9,- Museum, La Fundacion Rockefeller, Chapingo, Mexico 10,-Instituto del Biologia, Largo de Chapultepec, Mexico, D. F. 11,-Museum, Department of Emtomology, University of California, Berkeley, California A summary of the collection data of E. aurlfer fur­ nished by the above museums containing identified speci­ mens of this species is given in Table IX. Although the collection data accompanying many of the specimens listed 68

Is Incomplete, all, with the exception of a specimen In the British Museum labeled ”Sierre de Durango, Mexico” , are from the south-central portion of Mexico. The author found E. aurlfer to be limited in its distribution to the valloys of Mexico, Mesquital, Tehuacan, Morelos and Morelia in south-central Mexico (Table X and Figure 17). Within these valleys, It appeared to be fur­ ther restricted to local areas where alfalfa was grown. Collections made on wild plants In the regions bordering alfalfa growing areas were successful; however, collect­ ions made at random at a distance of a mile or more from alfalfa were, without exception, unsuccessful. As E. aurlfer was described originally from Mexico in 18)4.0 , prior to the introduction of alfalfa, there must exist, or have existed, one or more native plants upon which the larvae are capable of developing. However, as this species is now thought to develop and occur regularly on alfalfa, distribution was determined by examination of representative fields in the major al­ falfa producing areas. These areas, as shown in Figure

1 8, were located through the assistance of Drs. J. B. Pitner and Reginald Laird, Agronomists with the joint office of the Mexican Department of Agriculture and The Rockefeller Foundation. About 2,000,000 tons (U. S.) of alfalfa are produced 69 yearly on approximately 100,000 acres in Mexico (Hudson 1950). To clarify the map showing the commercial alfalfa producing regions of Mexico (Figure 18), the major areas are located as follows: (1.) area to the north and east of Mexico City, situated in the Distrito federal and state of Mexico; (2.) the southern portion of the state of Tlaxcala, and throughout the northern and central portions of the state of Puebla; (3.) immediate vicinity of the city of Oaxaca, Oaxaca; (Ij..) "Aguas Negras" re­ gion near Actopan, Hidalgo; (5.) "Hi Bajio" region in the states of Guanajuato and Queretaro; (6.) "La Laguna" area centered around Torreon, Coahuila; (7») Yaqul valley area in southern Sonora; and (8.) areas around Zamora and Moralia, Michoacan. Table IX A list of the collection data obtained for E» aurlfer from the U.S. National Museum, British Museum, and the Museum of La Fundacion Rockefeller*

LOCALITY DATE COLLECTOR COLLECTION

Progress©, Mor. V 27 A 8 A. C. Smith La Fundacion Rockefeller Museum Chapingo, Mexico Puente de Ixtla, Mor. June H. H. Smith British Museum (Natural History) London, England Cuernavaca, Mor* 7/7/1900 C. C. Dean Collection, U.S.N.M. Washington, D.C. Cuernavaca, Mor* Salle British Museum (Natural History) Cuernavaca, Mor. --- Hoege Wickham Collection, U.S.N.M. Cuernavaca, Mor. June H. H. Smith British Museum (Natural History) Mexico, Mexico June, 1922 E. G. Smith U. S. N. M. Esperanza, Mexico --- Hoege U. S. N. M. Esperanza, Mexico --- Hoege British Museum (Natural History) Frugus, Mexico --- U. S. N. M.

Chapingo, Mexico 9/15A8 A. C. Smith La Fundacion Rockefeller Museum Chapingo, Mexico --- F. Pacheco La Fundacion Rockefeller Museum Table IX- Continued

LOCALITY DATE COLLECTOR COLLECTION

Pueblo U. S. N«, M. Distrito Federal J. R. Inda Collection, U.S.N.M.

Distrito Federal mm ~ m a m e» L« Cenradt U. S. N.. M. San Angel, D.F. Wickham British Museum (Natural History) Omilteme, Gro* July H. H. Smith British Museum (Natural History) Tepetlapa, Gro« H. H. Smith British Museum (Natural History) Izuear de Matamoros, Pue. — - Hoege British Museum (Natural History) Mexico ----- Salle British Museum (Natural History)

Mexico, Puebla ----- Salle British Museum (Natural History) Mexico, Etla ---- - Salle British Museum (Natural History) Mexico, Izuear Salle British Museum (Natural History)

Mexico, Orizaba — --- Salle British Museum (Natural History) Mexico, Oaxaca Salle British Museum (Natural History) Mexico. Sierre de Duran«o — - British Museum (Natural History) Table X A list of the collection data obtained for E* aurlfer by the author in Central Mexico during 1952 and 1953*

Approx* Alt* Date of Host Locality in Meters Collection (Feeding) La Patera, D* F* 221+0 May 29, 1952 Alfalfa Mexico, D. F* 221+0 June 10, 1952 Alfalfa

Puebla, Pue* 2100 July 30, 1953 Alfalfa Tecamachalco, Pue* 2000 July 30, 1953 Alfalfa Azucar de Matamoros, Pue* 1550 July 2, 1953

Chaplngo, Max* 2200 July 27, 1953 Soybeans Texcoco, Mex. 2200 July 29, 1953 Alfalfa Chaleo, Mex* 2200 June 22, 1953 Alfalfa Amecameca, Mex* 2250 Sept. 21, 1953 Alfalfa Toluca, Mex*~ Rancho S* Antonio 2675 June 15, 1953 Alfalfa Toluca, Mex*« Rancho El Carmen 2675 June 15# 1953 Potatoes Table X- Continued A list of the collection data obtained fop B. aurlfer by the author In Central Mexico during 1952 and 1953*

Approx, Alt, Date of Host Locality (in Meters) Collection (Feeding)

Tlaxcala, Tla. 2100 July 3, 1953 Alfalfa

Actopan, Hgo, 20 I4.O Sept. 22, 1953 Alfalfa

Ixmilqullpan, Hgo* 2000 Aug. 5, 1953 Alfalfa

Cuernavaca, Mor, 1600 June 13, 1953 Amaranthus sp

Cuernavaca, Mor,- Km, 89 1500 July 9, 1952 Alfalfa

Zamora, Mich* 1500 Aug. 12, 1952 Corn Moralia, Mich* 2150 Aug* 25, 1952 Alfalfa Figure 17*- Map of the Republic of Mexico showing the distribution of E* aurlfer* I

vn

EPICAERUS AURIFER (BOH-)

. . . -t

• Areas Visited No Insects Found

a Areas Visited Insects Collected £ Serious Infestation On Commercial Scale 76

Figure 18♦- Map of the Republic of Mexico showing the commercial alfalfa producing areas* EPICAERUS AURIFER (BOH.) 78

Control

Cultural

A general review of the life history and habits of E. aurlfer indicates several apparent approaches toward control, by cultural means, of this pest.

The long incubation period of the egg required for hatching, and the exposed position of the egg masses would suggest several cultural practices designed to destroy the eggs, such as heavy grazing or cutting at the time the egg masses are most abundant. Also, the gregar­ ious habits of the adults, their slow and awkward means of locomotion, and their inability to fly might also be used to advantage in restricting the movements of E. aurlfer.

Chemical

Laboratory A series of laboratory tests were conducted, prior to the field tests, to determine the general rel­ ative toxlcitles of selected contact insecticides against the adult beetles. These tests, following the techniques used by Morrison (l9l|5) and Stringer (l9ij.9), Tor screening contact insecticides, consisted of saturating filter papers with known quantities and concentrations of Insecticides 79 and exposing the insects to the treated papers for a given period of time.

The laboratory tests were conducted at Chapingo during June, 1952. Female beetles, collected from the biological study area at La Patera were used in the tests. The following materials and concentrations were used in the tests:

1.- 0.5 per cent parathion

2.- 1.5 p©r cent E.P.N. 3.- 1.5 per cent DDT. 1|..- 2.5 per cent Dl/T.

5.- 0.5 per cent BHC. 6.- 1.5 per cent BHC,

7«- 1.5 per cent toxaphene

8.- 1.5 per cent chlordane

9.- 1.5 per cent dieldrin 10.- 1.5 per cent aldrin

11.- 1*5 per cent methoxychlor The tests were replicated 8 times and each replicate consisted of 10 beetles. The treated filter papers (15 centimeters in diameter) were allowed to dry for 15 hours prior to the test. Ten beetles were introduced under a petri dish (12.5 centimeters in diameter) inverted over a treat­ ed filter paper. The beetles were allowed to remain in contact #ith the treated papers for 1 hour, after which 80

they were removed and clean and untreated papers put in

their place. Observations and mortalities were recorded

at intervals of 1, 6, 2ip, and lj.8 hours. An untreated check

was Included in each test.

The tests, as summarized in Table XI, were not statistically analysed as they were preliminary in nature

and designed only to indicate which materials might warrant further testing in the field. Toxaphene, BHC, aldrin, and chlordane appeared prom­

ising, under the conditions of the laboratory tests, and

for that reason, were included in later field tests.

Field

Two general methods of application of the in­

secticides were employed in the field tests. The toxicant

was mixed in the seedbed in which alfalfa was to be sown, or it was applied to the foliage of the plant when the

adult beetles were present. The soil applications were

designed to control the larvae; the foliage application was designed to control the adult beetles, thereby prevent­

ing oviposition and a subsequent infestation. Application of Insecticides to the Foliage

This experiment involved the use of a series of plots arranged in the form of a randomized block, with each

treatment being replicated times. The experiment was 81

conducted at La Patera on a 2-year-old field of alfalfa, of the variety Oaxaca, adjacent to the biological study area. The roots of the alfalfa In this field had been previously found to be uninfested; however, many beetles had migrated into the field from surrounding heavily

infested fields. Each plot was 25 feet by 50 feet in size.

The following materials and concentrations were used in the test*

1.- 5*0 per cent DDT.

2.- 20.0 per cent toxaphene 3«- P©r cent BHC

I)..- 2.5 per cent aldrin 5»- 10.0 per cent chlordane The test materials were applied as dusts with a Hudson rotary hand duster June 26, 1952. The results of the treat­ ments, expressed as live beetles per square meter, are summarized in Table XII. These counts were taken iq.8 hours following the application of the materials. All of the insecticides resulted in a consistent high control (90 per cent or better reduction compared with the check) of the adult beetles.

Applications of Insecticides to the Soil

Small Plot Experiment -- - This experiment was 82 designed in the form of a randomized block, each treatment being replicated ij. times. The plots were each 10 meters by 10 meters in size. The field in which this experiment was conducted was prepared as a seedbed for alfalfa. The insecticide treatments were applied June 10, 1952, to the surface of the soil, as dusts, and raked into the top 2 to 3 inches of soil. An effort was made to sprinkle the materials evenly over the soil in each of the plots, and to vary the direction of raking so that the materials would be more uniformly distributed over the plots. Imme­ diately following the application of the materials, the field was sown In alfalfa of the Oaxaca variety.

The following materials and concentrations were used In the test: 1.- Aidrin, 2.0 pounds actual per acre rate

2.- Aidrin, 5*0 pounds actual per acre rate bieldrin, 2.0 pounds actual per acre rate Ip.- Dieldrin, 5*0 pounds actual per acre rate 5. BHC, 1.0 pound of the gamma isomer per acre rate

6.- BHC, 3*0 pounds of the gamma isomer per acre rate

7«- Toxaphene, 10.0 pounds actual per acre rate 8.- DDT., 10.0 pounds actual per acre rate

9*- Chlordane, 8.0 pounds actual per acre rate The effects of the materials In reducing the injury of the larvae to the primary roots was determined October 83

10, 1953, by examining the roots of 100 plants from each plot. These figures are summarized in Table XIV. The degree of infestation in the plots, including the untreated check, was extremely low 10 to if. per cent injury) and as a result, no evaluation of the treatments could be made.

Unreplicated Large Plot Experiment

This test was designed to determine the effect­ iveness of three materials: aidrin, dieldrin, and BHC, at rates of 9 pounds, 9 pounds, and 3 pounds of the gamma isomer per acre respectively, in controlling the larvae, when applied on a field basis with standard farm equipment. The plots were unreplicated and each was slightly over 1 acre in size. To determine the effectiveness of the treatments, the infestation counts were taken from if. locations within each plot.

The materials were applied April 25, 1952, as dusts on a newly-prepared seedbed, with a 12-foot "Evenflo" distributor, and mixed into the top 2 to 6 inches of soil with a tractor-drawn disc harrow. Alfalfa, of the variety Oaxaca, was immediately sowed upon the treated soil.

The degree of injury, as summarized in Table XIII, was determined by examination of the primary roots, 100 being taken from if. areas in each plot, October 10, 1953* As in the small plot soil application test, the level of 31*

infestation was too low (2 to 9 per cent injury) to eval­ uate the materials.

No phytotoxic effects of the insecticides, in either the foliage application test or the soil application tests, were observed. Table XI Results of preliminary laboratory treatments, expressed as per cent control, against the adult stage of Eh aurlfer. Chaplngo, Mexico, June 1952.

Treatment and Replicates Concentration 1. 2. 3* U. 5. 6. 7. b'.______Per cent Control 0.5# parathion 10 10 0 20 0 10 0 0 6.25

1.5# E.P.N* 0 0 0 0 0 0 0 0 0

1.5# DDT. 10 0 20 10 10 20 20 10 10.0

2.5# DDT. 20 10 3 0 20 10 ko 20 20 21.2

0.5# BHC 50 60 50 70 50 60 ko 90 58.8 1.5# BHC 14-0 50 i^o 80 70 5o 100 90 65.0

1.5# toxaphene 30 50 ko 20 50 30 30 ko 36.25

1.5# chlordane 10 20 30 10 ij-o 30 10 10 20.0 1.5# dieldrin 0 20 0 20 10 10 0 10 8.75 1.5# aidrin 20 fco 10 20 20 30 20 0 20.0 1.5# methoxychlor 0 0 0 0 0 0 0 0 0 Untreated check 0 0 0 0 0 0 0 0 rnmm** Table XII Results of foliar insecticide treatments for control of E. aurlfer adults, La Patera, D.F., June 26, 1952#

Pounds Live Beetles Per Square Meter Per cent Treatment and per Replicates Reduction Concentration_____ Acre______1* 2. 3. lu 5. Mean____ Over Check 5$ DDT* dust 22 2 1 1 1 1 1*2 91 20$ toxaphene dust 2k 0 2 0 2 0 o.e 9k 3$ BHC dust 20 0 1 0 0 2 0*6 96 2*5# aidrin dust 23 0 2 2 1 2 i*tv 90 10$ chlordane dust 20 0 1 1 2 0 0.8 9k Untreated check — 13 10 13 19 13*8 -- Table XIII Per cent of alfalfa primary roots injured by the larvae of E* aurifer following soil application of insecticides, ]La Patera, June 10, 1952*

Treatment and Replicates Amount per Acre 1. 3 • .... Mean 2*0 pounds aidrin 3 1 2 2.5 5.0 pounds aidrin 2 0 3 1 1.5 2*0 pounds dieldrin 0 2 1 2 1.25 5.0 pounds dieldrin 0 1 1 1 0.75 1«0 pound BHC (g.i.) 1 2 1 0 1.0 3*0 pounds BHC (g.l«) 2 0 0 1 0.75 10 pounds toxaphene 3 2 1 2 2.0 10 pounds DDT* k 0 3 1 2.0 8.0 pounds chlordane 0 1 0 2 0.75 Untreated check 2 3 3 3 2.75 Table XIV Per cent of alfalfa primary roots injured by the larvae of aurifer following soil application of insecticides, La Patera, April 25* 1952*

Treatment and Multiple Determinations Amount per Acre______1# 2» 3» lt+______Mean

9*0 pounds aidrin 6 9 1 8 6*0 9*0 pounds dieldrin 7 8 k 1 5.C 3*0 pounds BHC (g*i,) 6 9 8 5 7.0

Untreated check 2 9 7 3 5.25 89

SUMMARY AND CONCLUSIONS

The biology, ecology, distribution, and control of the weevil, Eplcaerus aurlfer Boheman, was studied in south-central Mexico over a 2-year period. This insect was found, for the first time, to be a local but serious pest of alfalfa. The principal damage to alfalfa was noted to be a result of the feeding of the larvae on the primary root. Injury by this means results in the complete destruct­ ion of the central portion of the root, and eventually, the death of the injured plant. The adults have also been noted in the field feeding upon the following crops: com, beans, wheat, and soybeans, and upon the following wild plants: Solanum rostratum L., Anoda hastata Cav., Eruca satlva Lam., Rumex obtusifollus L., Malva parvlflora L.,

Paspalum sp., Abutilon sp.. Cucumls sp., and Amarantus sp.

Under caged conditions in a food preference test the adults were found to eat, in descending order of preference, the foliage of beans, corn, alfalfa, tomatoes, wheat, and pota­ toes. This insect has one complete generation a year. The adults appear in late May or early June, and within 2 weeks following emergence, the adult population is at its peak. At this time, the sex ratio is approximately equal. 9 0

At the time the adults are last seen in the field, the latter part of September, there are approximately three times as many females as males.

Copulation commences 2 to Ij. days after emergence and eggs are produced 3 to 7 days later. The eggs, de­ posited in the form of a linear or ovoid mass, on the underside of the leaf, within the trough formed by a folded leaf or leaflet, or between two leaves, contain an average of 26 eggs, fertilization is required for the production of viable eggs and a fertilized female produces an average of 2.17 egg masses per season. In the field, egg masses have been collected from alfalfa, corn, beans, and a member of the pigweed group, Amarantus sp. Of these plants, the larvae are apparently only capable of developing on alfalfa. The incubation period of the egg is approximately 30 days. Upon hatching, the larvae immediately make their way into the soil.

The number of larval instars was found to be l\.; the winter being passed in the 3rd or i^th instar, or occasionally as a newly formed pupa. The pupal stage, lasting from 3 to ij. weeks, usually occurs during the month of May. The pupa is found In an ovoid earthen cavity at a depth of \ to inches below the surface of the ground. 91

Natural enemies were found to be Important in reducing

the field population of E. aurifer. Laboratory and field observations indicate that 2 species of skunks, Spllogale

sp. and Maphltis sp.. are important predators of this pest.

Under caged laboratory conditions, a ground squirrel,

Cltellus mexlcanus mexlcanus and a shrew, Sorex saussurel

saussurel Merriam were also observed as predators. A

mite, identified as belonging to the family Parasitidae, was observed as an external, apparently non-lethal parasite

of E. aurifer.

The distribution of this weevil, as determined by field collection and summarization of museum data, was found to be limited to the south-central portion of Mexico. From collections on alfalfa, it was found to be present in the valleys of Mexico, Mesquital, Tehuacan, Morelos, and Morelia.

Preliminary control studies utilizing organic insect­

icides were conducted in the laboratory and field. Labora­ tory tests against the adult beetles indicated that BHC,

Toxaphene, DDT., chlordane, and aidrin might be worthy of further field study. Foliar applications of these promising materials, as dusts on alfalfa, against the adult beetles,

resulted In a uniform, high (90 per cent or better) degree of reduction over the check. Both small plot and large plot field tests, employing 9 2

the mixing of the toxicant, formulated as dusts, in the seedbed prior to the sowing of alfalfa, were conducted.

Evaluation of these plots was not possible, however, because of the low level of larval injury to the roots. 93

APPENDIX

Figure 1*- Climograph for Texcoco, Mexico* Figure 2*- Climographs for Toluca, Mexico and Mexico D.F. Figure 3*- Climographs for Pueblo and Tehuacan, Puebla* Figure Ij.*- Climographfl for Cuernavaca and Cautla, Morelos* Figure 5*- Climographs for Zamora and Morelia, Micho&can. Figure 6*- Climographs for Actopan and Pachuca, Hidalgo* 9 k

CLIMOGRAPH FOR TfiXCOCO M ei.- Mean Annual Precipitation768 mm. Mean Annual Temperature 16 I*.C____ ALTITUDE ------2240 Mta

IAN. a a: a. <

J ULY.

Appendix Figure 1 95

- IMIJ..HM'.' * ■>» TulUCfl Mil.— CLIMOGRAPH FOR Cd.M««lca DF (Taeuhaya) Me >• n n u a i P r e c ip it o h o n78 ^ IB IB M « o n A n n u o l P r • c i p if o t t o7 nB S m m. Mion ^e'npptjtur* 187------£ Mton Annual Temperature—14^ Zfi_____ Al T I I kvL ------887ft Utl ALTITUDE______2308 MU

j(AN JAN.

JULY. JULY.

Appendix Figure 2 96

Climograph fo r PutMt Pui- CLIMOGRAPH FOR TAhuflgaw Pum M«on Annuol Prtciptlolion OQt mm Mean Annual Precipitation47M mm. M to n Annuo I 16.2*____ C Moan Annual Tampiratura lA i C ALTITUDE ______EI9Q l i l i i A LT IT U O E ______1 1 2 1 M il |AN (AN

T

JULY. JULY.

I

Appendix Figure 3 97

CLIMOi.HAf'H roR Cunutla Mor. M»on Annuol Precipitation 843 m m. CLIMOGRAPH FOR CuernflWflCfl Mnr itnn A • i lt’^nperotufe 21 9 *C Mton Annuol Precipitation 1Q4Q mm. A. ■*. ! DDE ____ Mean Annua I Temperature 2Q.3*C_____ A LT IT U D E ______1538 MU. jiAfiL JAW

JULY. JULY.

A p p e n d i x Figure ij. 98

CUW-.GRAPH FOR ZtfflgfQ MjCtl- CLIMOGRAPH FOR M O flifl Mich. Macn Annuol Proc ipitotion 826 __ym Moon Annuol Procipltotton 833 mm, Mean Annual T empgrotuf e .. 2.Q-Q fi— Moan Annuol T«mp»nitun I72*c ALTiiuDE ______1564 M U A LT IT U D E ______1823 Mlfc

lAN JAN.

/

JULY. JULY.

Apperxl ix Figure 5 9 9

CLIMOGRAPH FOR Aetanan Han. CLIMOGRAPH FOR PflfihllM Hflflt Moon Annuol Proelpitolion Meon Annuol Precipitationa ib y m — Moon Annual Temper of ure_JU6JLjfi____ Moon Annual Temperature 152 ____..C altitude ______191* Htl A L T IT U D E 24QQ MH.

JAN. JAN.

JULY. J ULY.

Appendix Figure 6 100 Literature Cited

Blackwelder, R* E. 19lf7* Checklist of the Coleopterous Insects of Mexico, Central America, The West Indies, and South America* U. S. Nat. Bui* 185, Part 5, 797• Boheman, C. H* l81|.0* Schonherr Genera et Species, Cur- culionidium* Vol* VI, Part 2, p* 278* Chapman, R. N* 1939* Insect population in relation to insect outbreak* Ecol* Monog* 9(3):261-269* Contreras Arias, A* 19lf2* Mapa de las provincias climato- logicas de la Republica Mexicans, Sria* de Agric# y Fomento* Direccion de Geografia, Meterorologia e Hldrologia, Inst* Geografico, Mexico D. F* Dalla Torre, K. W. von and M. F* von Qnden. 1936* Coleo- pterorum Catalogus* pars llf7, P* 14-2 * Dyar, H* G* 1890* The number of molts of lepidopterous larvae. Ann* N. Y. Acad* Sci*, Vol. VIII, pp* 19!+.-232* Hudson, G. D* 1950* Encyclopaedia Britannica World Atlas, Unabridged* Published by Encyclopaedia Britannica, Inc*, Chicago, 111* Leavenworth, W. C* 1931* Vegetation of Nuevo Leon* Am* Midi* Nat. 21:688-729* Leng, C. W* 1920. Catalogue of the Coleoptera of America, North of Mexico, (inc. Supplement if)* Published by J. D. Sherman, Jr*, Mount Vernon, N.Y. Leopold, A. S. 1950. Vegetation Zones of Mexico* Ecology 31 (if): 507-531* Morrison, F. 0. 19l|5* Comparing the toxicity of synthetic organic compounds* 7oth* Ann* Rep* of Ent* Soc* of Ontario, p* 18* Munna, E. N* 1922* Climatic phenomena* Monthly Weather Review 50(9): 1*77-6.81* Peterson, Alvah* 191+7• A Manual of Entomological Equip­ ment and Methods* Part I and II* Edwards Bros* Inc*, Ann Arbor, Michigan* 101

Sharp, David* 1891* Biologia Cantrail-Americana. Coleop- tera. Curculionldae, Vol* IV, Part 3 (1889" 1911), P. 119. Stringer, A* 19ij-9. A simple method of assaying contact toxlcltles of insecticides, with results of tests of some organic compounds against Calandra granarla L* Ann* Appl. Biol. 36: 213* Transeau, E* N* 1935. The prairie peninsula* Ecology 16(3): lj.23-ij.37. Wellhausen, E* J. et al* 1951* Razas de malz en Mexico, su origen, caracterlstlcas y distrihuclon. Folleto Technico 5, Of* Est* Especlales, S*A*G*, Mexico D* F. 102

AUTOBIOGRAPHY

I, George Mallory Boush, was born in Norfolk, Virginia,

June 5, 1926. I received my secondary school education in the public schools system of Princess Anne County, Virginia.

During World War II, I enlisted in the U. S. Army Air

Corps, and served as Aviation Cadet from June ll+, 19^1 to

November 8, 191+5* My undergraduate training was obtained at Virginia Polytechnic Institute, Blacksburg, Virginia, from which I received the degree Bachelor of Science in

191+8* From The Ohio State University, I received the degree

Master of Science in 1951* While in residence at The Ohio

State University, I held the position of Research Fellow with the U. S. Public Health Service from October 1, 1950 to March l5» 1952. From April 1, 19U9 to September 30, 1950

I was employed as Assistant Entomologist at the Tidewater

Field Station, Virginia Agricultural Experiment Station at

Holland, Virginia; and from April 1, 1952 to December 1,

1953 was employed as Assistant Entomologist with the \ Mexican Agricultural Program of the Rockefeller Foundation in Mexico City, Mexico, since January 1, 1951+ I have held the position of Assistant Entomologist at The Kentucky

Agricultural Experiment Station, Lexington, Kentucky.