Reproductive biology of the lesser cornstalk borer, Elasmopalpus Lignosellus (Zeller) (Lepidoptera: Phycitidae)

Cathleen Martyniak
UF Dissertation Project
Preservation Department
University of Florida Libraries
P.O. Box 117008
Gainesville, FL 32611-7008

Dear Ms. Martyniak:

I am pleased to learn of the UF Dissertation Project, and to make my "aged"
dissertation available for researchers. However, there are two errors that must be
corrected to successfully raise larvae of the lesser cornstalk borer using the methods
listed. On page 13, the first sentence of the first full paragraph should read:

Each cage with pupae was numbered and put in a culture room at 30 + 1 degrees
centigrade, 30 % relative humidity, and daily photoperiod of 13 firs light.

I hereby authorize you or whomever you appoint to make these changes.

Thank you for your assistance. I wish you the best of success with this new
project.

Sincerely,

Karl J. Stone

REPRODUCTIVE BIOLOGY OF THE

LESSER CORNSTALK BORER,

ELASMOPALPUS L IG NO SELL US (ZELLER)

(LEPIDOPTERA: PHYCITIDAE)

By
KARL JOHNSON STONE

A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF

THE UNIVERSITY OF FLORIDA

IN PARTIAL FULFILLMENT OF THE REQUffiEMENTS FOR THE

DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA
1968

ACKNOWLEDGEMENTS

I greatly appreciate the advice and criticism offered by Dr. T. J. Walker,
chairman of my supervisory committee, during the research and preparation of the
dissertation,.

Appreciation is gratefully extended to Dr. L. A. Hetrick and Dr. J. T.
Creighton, Deparrment of Entomology; Dr. D. B. Ward, Department of Botany;
Dr. G. C. LaBrecque, United States Department of Agriculture, Entomology Re-
search Division; and Dr. H. K. Wallace, Chairman of the Department of Zoology,
who served as members of the supervisory committee.

Appreciation is extended to Dr. W. G. Eden, Chairman of the Department
of Entomology for providing assistants who helped maintain the insect colony.

Special thanks is expressed to Mr. J. Beckner, Department of Botany for his
assistance in botanical nomenclature, and to Mr. P. U. Roos for assistance in
translating French and German material.

Sincere gratitude is extended to my wife for her generous assistance, patience,
and constant encouragement involving long hours end many sacrifices.

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ii

LIST OF TABLES v

LIST OF FIGURES vi

INTRODUCTION ]

REVIEW OF LITERATURE 3

General References 3

Host Plants r"3)

MATERIALS AND METHODS 12

Rearing Techniques 12

General Methods 12

Aberrant Pupae 19

Other Materials and Methods 21

MORPHOLOGICAL STUDIES 22

Morphology of the Reproductive System 22

Materials and Methods 22

Results and Discussion 22

Male 22

Female 26

The Spermatophore 29

Materials and Methods 31

Results and Discussion 31

Primary Simplex and Spermatophore Color 33

Materials and Methods 33

Results and Discussion „ 34

Egg Development and Position Relative to Age 35

Materials and Methods 37

Results and Discussion 37

iii

Morphology of the Tympanic Organ 39

Materials and Methods 40

Results and Discussion 40

BEHAVIORAL STUDIES 45

Mating Cage Conditions 45

Materials and Methods 45

Results and Discussion 46

Mating Behavior 48

Materials and Methods 49

Results and Discussion 50

Influence of Additional Females on Male Mating Frequency ... 54

Materials and Methods 54

Results and Discussion 55

Influence of Age on Mating 55

Materials and Methods 56

Results and Discussion 56

Influence of Male Antennectomy on Mating 56

Materials and Methods 58

Results and Discussion 58

Longevity of Virgin and Mated Moths, Spermatophore Passage and

Acceptance, and Fecundity 58

Materials and Methods 59

Results and Discussion 60

Time of Oviposition 76

Materials and Methods 77

Results and Discussion 77

Response of Adults to Sound 77

Materials and Methods 80

Results and Discussion 82

SUMMARY 85

LITERATURE CITED 88

BIOGRAPHICAL SKETCH 95

LIST OF TABLES

Table Page

1 Reported host plants of the lesser cornstalk borer 6

2 Composition of medium for lesser cornstalk borer larvae 16

3 Color fluid in the 1st secretory area of the primary simplex of 3-

day-old mated and unmated lesser cornstalk borer males at dif-
ferent periods of the day following mating the previous night. . . 36

4 Cage conditions and spermatophores passed by 2-dcy-old fed and

unfed lesser cornstalk borer adults, tested for 4 nights in 40-dr

vials, 1 pair per vial, 22 replicates per test 47

5 Longevity of lesser cornstalk borer adults 61

6 Spermatophore passage and acceptance during the lifetime of various

Lepidoptera 63

7 Fecundity of the lesser cornstalk borer. 69

8 Lesser cornstalk borer females showing 2 or more variations from

basic population oviposition patterns 73

LIST OF FIGURES

Figure Page

1 Cages used in rearing technique. A. Matlng-oviposifion cage.

B. Rearing cage 14

2 VeniTal view of terminal pupal abdominal segments of the lesser

cornstalk borer. 18

3 Reproductive system of the male lesser cornsfalk borer 25

4 Reproductive system of the female lesser cornstalk borer. ... 28

5 Spermatophore of the lesser cornstalk borer 32

6 Egg development and position in the reproductive tract of lesser

cornstalk borer virgin females relative to age 38

7 External anterior view of the first abdominal segment of the lesser

cornstalk borer moth illustrating the tympanic organs on the ex-
cised abdomen. 43

8 Internal lateral view of the right tympanic organ of the lesser

cornstalk moth with the lateral wall of the tympanic sac removed . 44

9 Percent mating of 1-6-day-old lesser cornstalk borer adults caged

for 1 day 57

10 Mated lesser cornstalk borer male longevity and spermatophores

passed 64

11 Mated lesser cornstalk borer female longevity, oviposition period,

fecundity, and spermatophores accepted 65

12 Total number of spermatophores passed per day by 25 lesser corn-

stalk borer males, number of males after day 14 as indicated. . . 67

13 Average numbers of eggs laid per day by 25 lesser cornstalk borer

mated females, number of females after day 12 cs indicated. . . 71

vi

F?9ure Page

14 Diurnal and nocturnal response of lesser cornstalk borer adults

to various amplitudes and frequencies 84

INTRODUCTION

The lesser cornstalk borer, Elosmopalpus lignosellus (Zeller), is an important
pest of crops in Florida, causing considerable damage to corn, soybeans, peanuts,
sugar cane, field peas, southern peas, and rye. The moth is widely distributed
throughout the tropical and temperate regions of the New World, including the
southern half of the United States from California to the Carol inas, north on the
East Coast to Massachusetts, and south thru Central America and South America to
Argentina, Chile, end Peru (Heinrich, 1956).

Damage to crops in Florida occurs primarily in areas with muck or sandy soils
(Strayer, J. R. ' 1968. Personal communication.). Luginbill and Ainslie (1917)
and Lyle (1927) found that damage usually seems greater on thin sandy soils in South
Carolina, Florida, and Mississippi. King et al. (1961) in Texcs reported damage is
especially severe during drought periods. Leuck (1966) in Georgia reported larvae
damage seedlings during drought and when late plantings are followed by hot dry
periods. Wide-spread infestations have led to several insecticidal investigations.

However, little is known about the moth's reproductive biology. Basic research
in this area was facilitated by rearing the insect in the laboratory and examining the
reproductive morphology with respect to structure and changes occurring when moths

Assistant Extension Entomologist, Institute of Food and Agricultural Sciences,
University of Florida.

2

mated or aged. In addition the morphology of the tympanic organ is discussed.

Behavioral studies included mating behavior and various factors which influ-
enced this activity: cage conditions, additional females on male mating frequency,
age, and male antennectomy. The longevity of virgin and mated moths, sperma-
tophore passage patterns, and fecundity were studied, as well as time of ovipo-
sition. Lastly, the response of adults to sound was observed.

The above information may facilitate studies on the effects of chemosterilants,
antimetabolites, and predator and parasite relationships.

REVIEW OF LITERATURE

General References

The literature contains considerable research on insecticidal control of the lesser
cornstalk borer, but little is known about its biology. Below are the papers that deal
with reproductive biology and rearing methods.

Luginbill and Ainslie (1917), using moths from South Carolina and Florida, dis-
cussed rearing methods and mating cage conditions, as well as longevity, fecundity,
and time of mating. Sanchez (1960), Dupree (1965), Leuck (1966), and Calvo (1966)
discussed similar factors with moths from Texas, Georgia, and Florida.

Host Plants

The lesser cornstalk borer attacks many weeds and crops, especially legumes and
grasses, throughout the southern half of the United States (King et al., 1961).

Table 1 lists 62 host plants of the lesser cornstalk borer. The following 14
families are represented: Chencpodiaceae, Convolvulaceae, Cruciferae, Cucur-
bitaceae, Cyperaceae, Gramineae, Iridaceae, Leguminosae, Linaceae, Malvaceae,
Pinaceae, Rosaceae, Rutaceae, and Solanaceae. Confusion in the taxonomy of culti-
vated plants and common names complicated compilation of the list, and in some cases,
the same host is listed under different common names to indicate common usage in
different parts of the country. In such cases, e.g. black-eyed beans = black-eyed

3

4
peas, the host is counted only once in the total count of hosts. Where varietal
names are available, each host is counted once. Scientific names were obtained
from standard references (Bailey, 1949; Fernald, 1950; Hitchcock, 1951) and
Hill's (1937) paper on cultivated sorghums.

Most authors consider the pest a subterranean feeder, but some reports suggest
feeding on the aerial parts of plants. Similar feeding behavior of other species
may have misled workers and confused host records. For instance, the phycitid
moth, Ufa rubedinella (Zeller) (=Elasmopalpus rubedinellus (Zeller)), redescribed
by Heinrich (1956) was reported feeding on leaves and fruits of lima beans and
black-eyed peas in Florida (unpublished records, Florida Department of Agriculture,
Division of Plant Industry, 1944-1945). The larva webs debris in a manner similar
to the lesser cornstalk borer, but the insect has not been reported in the DPI files
since 1945. Unidentified pyralid larvae were reported on peach seedlings by Dekle
(1965) with the characteristic sand-debris subterranean tunnels of E. lignosellus;
however, the tunnels also extended up the stems and over leaves.

Table 1 Notes

a U.S. Dep. Agr. , 1952-1968

b Reynolds, Anderson, and Andres, 1959

c Chitfenden, 1900

d Chittenden, 1903b

e Howard, 1900

f Vorhiesand Wehrle, 1946

g Isely and Miner, 1944

h Wilson and Keisheimer, 1955

i Keisheimer, 1955

j Bissell, 1945

k Bissell, 1946

I Lyle, 1927

m Luginbill and Ainslie, 1917

n Sanchez, 1960

o Riley, 1882 (as cited by Luginbill and Ainslie, 1917.)

p Riley, 1882a

q Riley, 1882b

r Dempsey and Brantley, 1953

s Forbes, 1905

t Webster, 1906

u Bissell and Dupree, 1947

v Leuck, 1966

w Chittenden, 1903a

x Heinrich, 1956

y Dupree, 1964

z King, Harding, and Langley, 1961

aa Arthur and Arant, 1956

bb Walton, Matlock, and Boyd, 1964

cc Cunningham, King, and Langley, 1959

dd Harding, 1960

ee Calvo, 1966

ff Cowart and Dempsey, 1949

gg Ash and Bibby, 1957

hh Stahl, 1930

Table l.-Repcried host plants of the lesser cornstalk borer

field

green

Scientific Name

Medicago sativa L.

Hordeum vulgare L.
Phaseolus sp.

Phaseolus I i mens is
Mac fad.

Phaseolus vulgaris L.

Localities

References

Ariz., Kans,
Tex.

Calif.

b.

Ala., Ariz. , Ark. , a,b,c,d,e,
Calif., Dela., f,g,h,i,j,

Fla., Ga., Md., k,l.
Miss., Mo., N.C.,
Okla., S.C.,
Tenn. , Tex. , Va.

N.C.

Vigna sinensis
(L.) Endl.

Calif.

Phaseolus vulgaris L.
var. humilis Alef.

Tex.

Okla. a.

Ala., Fla., Ga. , a.
Md., S.C., Va.

Tex. a.

Phaseolus vulgaris L,

Ariz.

Beta vulgaris L.

Fla.

Ala., Ark.,
Conn. , Ga. , Md.
N.C, Okla.,
S. C. , Tenn. , Va.

Calif., Ga.

Ala.

Table 1 Continued

Common Name

Scientific Name

Localities

References

Cabbage

Brassica oleracea L.
var. capitata L.

Fla.

a.

Cane,

Saccharum officinarium

Fla.

m.

Japanese

L.

sugar

Fla., La. , Miss.

a,l.

Cantaloupe

Cucumis melo L. var.
cantalupensis Naud.

Calif., Tex.

a,n.

Chufa

Cyperus esculentus L.
var. sativus Boeckl.

Fla.

m.

Citrus

Citrus sp.

Fla.

a.

Clover,
crimson

Trifolium incarnatum L.
var. elatius Gibelli
& Belli

Ga.

J-

Clover,
White Dutch

Trifolium repens L.

Fla.

a.

Cole
crops

Brassica sp.

Va.

a.

Corn

Zea mays L.

Ala., Ark.,

a,b,f,g,h,

field
silage

i / ■ /"■/ "/

Conn., Fla., Ga. , o,p,q,r,s.

III., La., Mass.,

Md., Miss., N.C.,

Okla., S.C., Tex.,

Va.

Fla., Ga. , Tex. a.

Ga. a.

Corn,
broom

Sorghum vulgare Pers.
var. technicum
(Koern.) Fiori &
Paoletti

Okla.

Table 1 Continued

Scientific Name

Localities

References

Sorghum vulgare Pers. Calif.

var. caffrorum (Retz.)
Hubbard & Render

Zea mays L. var.
rugosa Bonaf.

Ariz., Calif.,
Fla.

a.

Hibiscus gossypium L.

Calif.

b.

Vigna sinensis
~fL.) Endl.

Ala., Ariz. , Ark. ,
Fla. , Ga. , Miss. ,
N.C., Okla.,
S.C., Tex., Va.

a/d,f,g,h,
i,j,k,l,m,
t,u,v,w,x.

Linum usitatissimum L.

X.

Alopecurus pratensis L.

Ark.

g.

Gladiolus sp.

Fla.

i.

Echinochloa crusgalli
(L.) Beauv.

Ark.

g.

Cynodon dactylon
(L.) Pers.

Calif., Ga.

b,y.

Panicum texanum Buckl.

Tex.

a.

Diqitaria sanquinalis
(L.) Scop.

Ark., Calif.,
Fla. , Ga. , Tex. ,
Md.

a,b,g,h,n,

Sorghum halepense
(L.) Pers.

Ariz. , Calif. ,
Fla. , Miss. ,
Okla., Tex.

a,b,h,n.

Cyperus esculentus L.

Calif., Fla.

b,i.

Digitaria decumbens

Fla.

a.

Stent.

Table 1 Continued

Common Name

Scientific Nar

Localities

References

Grass,
Rhodes

Grass,
rye

Grass,
Sudan

Grass,
water

Chloris gayana Kunth Fla.

Lolium sp. Fla.

Sorghum sudanense Tex.
(Piper) Stapf

Cyperus sp. Calif.

Grass,
wire

Eleusine indica (L.)
Gaertn.

Ga., S.C.

Ground
burnut

Aegilops sp. ?

Tex.

Hegari

Locust,
black

Lupine

Lupine,
blue

Cyamopsis psoralioides Tex.
D.C.

Sorghum vulgare Pers. Ariz., Tex.

Robinia pseudoacacia L.

Lupinus augustifolius L. Fla.,Ga.
var. 'rancher'

Lupinus hirsutus L.

a,n.

Millet

Milo
maize

Oars

Oars,
wild

Panicum miliaceum L. La., S.C. a.

Sorghum subglabrescens Ariz., Tex. a,m.
(Sieud.) A. F. Hill-

Avena sativa L. Ala., Calif., a,b,n.

Miss., S.C. , Tex.

Avena barbata Brot. Calif. b.

or A. fatua L.

Table 1 Continued

10

Common Name

Scientific Name

Localities

References

Papyrus

Cyperus papyrus L.

Calif.

a.

Peach

Prunus persica
(L.) Batsch

Fla.

a.

Peanuts

Arachis hypogaea L.

Ala. , Ariz. ,
Calif., Fla.,
Ga„ , Miss. ,
N.C., Okla.,
S.C, Tex.

a,c,e,f,h,
i,l,n,y,z,

aa,bb,cc,
dd.

Peas

Pisum sativum L.

Ala., Ariz. ,
Ark., Calif.,
Fla., Ga., N.C.,
Okla., S.C, Tex.

a,b.

garden

Ala.

a.

winter

Tex.

a.

Peas,
Austrian

Pisum sativum L.
var. arvense (L.) Poir.

Tex.

a.

winter

field

Ala., Calif. ,
Fla., Ga. , Miss. ,
Tex.

a,n.

Peas,
black-eyed

Vigna sinensis
(L.) Endl.

Ala., Ariz. ,
Calif. , Ga. , Tex.

a,n.

southern

Ala.

a.

southern table

Ala.

a.

Pimento

Capsicum frutescens L.

Dela. , Fla., Ga.

a,j,i,r,ff.

Pine,
loblolly

Pinus toeda L.

Va.

a.

Potato,

sweet

Ipomoea baralas Lam.

Calif., Fla., Ga.

a.

Table 1 Continued

11

Common

Name

Scientific Name

Localities

References

Rice

Oryza sativa L.

Fla., La.

a.

Rye

Secale cereale L.

Fla., Tex.

a.

Sorghum

Sorghum vulgare Pers.
var. vulgare

Ariz. , Calif. ,
Fla., Ga. , La. ,

a,b,f,l,m,
t.

Miss., Okla.,
S.C, Tex.

Sorghum,
grain

Sorghum vulgare Pers. Ala., Ariz.,
var. vulgare Fla., Miss.,

N.C., Okla.,
S.C.

a/gg.

Sorghum,
Sudan

Sorghum almum Parodi Ga.

Soybeans

Stock,
garden

Glycine max (L.) Merr. Ala., Ariz., a, v.

Ark., Fla„, Ga. ,
La., Miss., N.C.,
S.C, Tex., Va.

Mafthiola sp.

Calif.

b.

Strawberries

Fragaria virginiana Ala., Ark., a,g,i,hh.

"Duch. Calif., Fla., Md. ,

N.C., N.Y.,

Tenn. , Va.

Tomatoes

Lycopersicon esculentum Fla., N.C. , Tex. a.
~MiTL

Turnips

Brass ice napus L.

Ala. , Ariz.
Fla., Ga.

i,f,h,m.

Vetch
Wheat

Vicia sp.

Tex.

Triticum oestivum L. Ala., Fla., a,h,m.

Okla. , Tenn. , Tex.

MATERIALS AND METHODS

Rearing Techniques
General Methods

Moths collected by Calvo (1966) in light traps near Gainesville, Florida,
were the original stock for this investigation. Individuals from this stock were
used to start a colony which was maintained for 7 months to establish a large
colony before experimentation began. The colony was maintained for 27 months
thereafter, representing a total of approximately 32 generations.

Several workers reared the insect thru its life history for 1 or 2 generations
(Luginbill and Ainslie, 1917; Sanchez, 1960; KingetaL, 1961; Dupree, 1965;
Leuck, 1966). Calvo (1966) reared several generations on a modification of
Berger's (1963) diet for Heliothis sp. Larvae were reared individually in vials.
Macerated corn seedlings were added to the diet every 3rd generation to avoid
pupal aberrations. Calvo (1966) collected eggs laid on paper thru screen topped
cages — the method adopted here.

Transparent plastic containers, 10x10x7 1/2 cm deep were used as mating-
oviposition cages (Fig. 1 A). Ten male and ten female pupae were placed in each
cage. A 14 x 18 mesh per inch galvanized screen stapled to a rim of wooden strips
was placed over the cage mouth. Two percent sucrose solution was supplied in a
wide-mouth pipette and soft rubber bulb (total capacity 4 ml) placed thru a hole

12

13
in the screen. This supply normally lasted 12 days. Immediately below the pipette
was a dish 4 cm in diameter/ held in place by masking tape in a rear floor corner.
The dish trapped sugar solution that might drop from the pipette. If spilled solution
coated the pupae, the adults could not emerge properly. Four mating-oviposition
cages were prepared on each of 5 days during the week.

Each cage with pupae was numbered and put in a culture room at 47 + 1 C,
30-50% relative humidity, and daily photoperiod of 13 hr light. The pipette bulb
was squeezed daily to release the air bubble that formed at the bottom, thus mak-
ing the solution available to the emerged moths. After 1 of each sex had emerged,
a paper sheet identified with the corresponding cage number was placed daily over
the screen top. One corner of the egg sheet was folded upward to allow space for
the protruding pipette bulb. The plastic cage top was placed diagonally over the
sheet to hold it down. Eggs were laid on the sheet through the screen and were
readily visible on the paper. After 7 of each sex emerged, this procedure was con-
tinued for 9 more days.

Egg sheets were removed daily and set aside on frays in the culture room for
24 hr. Egg color was used to differentiate between fertile and sterile eggs, since
fertile eggs turned from cream white to red, while sterile eggs remained cream color-
ed or turn red at 1 end only. The sheets were arranged in order on the basis of
mating cage number and those with less than 30 eggs or more than 10% sterile eggs
were discarded. To preserve genetic variability, the following system was used.
Sixteen sheets were selected from the remaining egg sheets and divided into 4 groups
of 4 each, with the lowest numbered sheet going to the 1st group, the next highest
to the 2nd group, and so on until distributed. Then 25 fertile eggs were cut from

14

Fig. 1. -Cages used in rearing technique. A. Maring-oviposition cage.
B. Rearing cage.

15

each sheer and each group was pur into a transparent plastic rearing cage. This
cage (Fig. 1 B), 12 1/4 x 17 1/4 cm by 6 cm deep was filled to about 12 mm depth
with medium, modified from Berger (1963).

A duo-speed Waring^blender, model 1002, with 1 liter containers was used
in media preparation. A blend was mixed in the order listed in Table 2. Blending
was at low speed thru and including addition of alphacel. Previously measured
ingredients were added without pause to avoid a highly viscous mixture. While the
agar cooled to about 41 C after removal from the autoclave (about 3 min, running
cool tap water over the flask containing the agar), the blender was run continuously.
The agar was then added with the blender running at high speed for the remaining
blending. The total mixing process took 6-8 min.

Medium prepared the day before use and placed under refrigeration was best,
as fresh medium had somewhat more moisture than optimum. Any moisture that con-
densed on the sides of the container when it was removed from the refrigerator was
wiped off. Otherwise, the water would cover the medium and ultimately kill the
eggs, young larvae, or both. About 250 ml of sifted, white, sterilized sand was
poured down the long axis of each cage, and the sand ridge was leveled off, leav-
ing the medium free of sand along the cage sides. The papers with 100 eggs of each
group were placed on the sand ridges. Next a sterilized paper towel was placed
over the cage rim, and a screen top was placed firmly over the towel. The screen
top was made by cutting out the center of the plastic container top and replacing
it with screen of the same mesh as used for the mating cages. The towel reduced
evaporation and the screen top prevented larval escape. To reduce evaporation
further, a 1.3 cm thickness of sterilized cellucotton was put over the screen top and
heid on with a large rubber band.

16
Table 2. -Composition of medium for lesser cornstalk borer larvae.

Distilled water 190.0 ml

KOH, 22.5% 4.3 ml

Casein, vitamin free 40.0 g

Wesson's salts 8.5 g

Sucrose 22.7 g

Formaldehyde, 10% 3. 1 ml
Solution of: 7 g methyl p-hydroxybenzoate and

7 g sorbic acid in 50 ml 95% ethyl alcohol 12.5 ml

Wheat germ 25.6 g

Alphacel (hydrolyzed purified cellulose, powder) 4.3 g

Agar, dissolved in 515 ml water 21.3 g

Vitamin diet fortification mixture0 8.5 g

Ascorbic acid 13.6 g

Streptomycin sulfate (700 micrograms/ml) 118.0 mg

a Nutritional Biochemicals Corporation, Cleveland, Ohio

17

After 21 days, the cage was opened, and the cellucotton, paper towel, and
medium were removed. The screen top was replaced and used as a sieve for rapid
separation of cocoons from the sand. The cocoons were hand picked from the re-
maining debris and placed in a small household sieve.

The sieve with the cocoons were dipped in dilute Chlorox^ solution (1 part
chlorox to 1 part water) for 45-60 sec and agitated to dissolve the silk and free
the pupae (Bartlett and Martin, 1945). After rinsing the pupae in water, the pupae
were dipped for 15-30 sec in 60% isopropyl alcohol. The pupae sank and the lar-
val exuviae were floated off. The pupae were spread on a paper towel to dry.

Separation plus extraction took about 15 min per cage.

After extraction and drying, the pupae were sexed by examining the terminal
abdominal segment (Fig. 2). Sexing was completed in 15 min per cage. Pupae
were then selected for mating-oviposition cages. No more than 5 pupae and no
more than 3 of 1 sex from a given rearing cage were put in 1 mating-oviposition
cage. Pupae at the same developmental stage, judged by color, were placed in a
given mating-oviposition cage so that adults would emerge about the same time.
Four cages per day 5 days a week were prepared, numbered, and put in the culture
room .

Females began ovipositing on the 2nd night after emergence. During the 9
days that a mating-oviposition cage was kept, about 80% of the eggs that would
be laid v/ere deposited on the egg sheers. Colony daily egg production was about
5000. Duration of egg, larval, or pupal stages was not recorded as production of
adults was the primary goal. Total time from egg deposition to adult emergence
was 24-28 days. Larvae consumed about 1/10 of the media. Production was low

Fig. 2. -Ventral view of terminal pupal abdominal segments of the lesser
cornstalk borer

19

for the 1st few generations, but after a few generations, 60 to 80 pupae were ob-
tained per cage.

The average duration from egg to adult, 26 days, was as short or shorter than
results reported to date. Luginbill and Ainslie (1917) in South Carolina recorded
38.5 days for the spring generation, and 64.6 days for the fall generation under
unspecified laboratory conditions, feeding larvae cowpea leaves. Spring temper-
atures ranged somewhere between 80-90 F diurnally and reached 80 F noctur-
nally. Sanchez (1960) in Texas reported 24.3 days during August, and 46.3 days
during September-October, feeding larvae peanut roots. Eggs were exposed to
70-100 F. Larvae were exposed to the following average daily minimum and
maximum temperatures: June, 77 and 92.3 F; July, 79.5 and 9o F; August,
79.5 and 94.5 F; September, 74 and 89 F. Pupae were exposed to temperature
ranges between the following minimum and maximum temperatures: July, 76-100
F; August, 66-102 F; September, 64 and 98 F. No temperature ranges were
mentioned for October. King et al. (1961) relied heavily on Sanchez for data and
gave little detail on methods. Dupree (1965) in Georgia recorded 47.8 days and
55 days during June-September in 1957 and 1958, respectively, feeding larvae
foliage and stem sections of seedling southern peas. Average minimum and maxi-
mum temperatures were 66.6 and 86.4° F in 1957, and 66.8 and 88.2° F in 1958.
Leuck (1966) in Georgia reported 32.8 4- 2.3 days, feeding larvae soybeans or
cowpea leaves. Monthly mean minimum temperatures ranged from 57.4 and 72.7°
F, monthly mean maximum 79.7 and 96.2 F.

Aberrant Pupae

Calvo (1966) found after rearing 3 successive generations, a small but unspecified

20
percentage of pupae appeared with poorly developed wing pads and light scleroti-
zation over the pupal 3rd and 4th abdominal segments posterior to the wing pads.
He found that the addition of macerated corn seedlings to the diet every 3rd gen-
eration eliminated pupal aberrations.

To determine the percent pupal aberrations and percent successful emergence
from aberrant pupae occurring with my rearing technique after 23 generations, the
following experiment was conducted.

Groups of pupae extracted on each of 6 days were examined. Aberrant pupae
were described as below and place in numbered 4-dr vials, and the vials with pupae
were placed in the culture room until adult emergence or death. Dead pupae be-
came discolored and shriveled. Normal pupae not used in colony maintanence were
used as controls and were handled in the same manner but not numbered.

All aberrations were on the pupal venter. These 4 categories v/ere recognized:
(A) a lightly sclerofized area between the 3rd ana/or 4th abdominal segment and
the wing pads and appendages; (B) a lightly sclerotized area between the 3rd and/or
4th abdominal segment and 1 or more appendages but not wing pads; (C) a lightly
sclerotized area between 2 or more appendages or between a wing pad and append-
age; and (D) 1 or more bright green appendages in an otherwise uniformly colored
pupa.

Of 1721 pupae extracted, 5% of the male and 6% of the female pupae had
aberrations. Fifteen percent of aberrant pupae exhibited 2 or more aberration types.
Seventy-two percent of the males and 84% of the females emerged successfully, i.e.,
with wings fully expended and with normally formed appendages. In the controls,
93% of the males and 92% of the females emerged successfully.

21

The low percent pupal aberrations and the high percent successful emergence
from aberrant pupae indicated the rearing technique was adequate.

Other Materials and Methods

Specific materials and methods are outlined under the appropriate sections be-
low. However, a few general procedures that were used in several experiments
are mentioned here.

Pupae not used to maintain the colony were placed in 4-dr 20 x 70 mm glass
shell vials, each with a small wad of cotton, and the vials were stoppered with
cotton plugs. When moths emerged, the cotton wad was saturated with 2% sucrose
solution. Adults were used the same day they emerged or were held in the 4-dr
vials until they reached an age desired for experimentation.

In experiments involving mating and longevity of virgins, moths were placed
in 4.7 cm x 8.5 cm 40-dr clear plastic vials. A wad of cellucotton was placed
in the vial bottom and was saturated with 2% sucrose solution. The vial mouths
were closed with squares of cellucotton 1/2 mm thick held in place with rubber
bands. The vials with moths were then placed vertically in enameled pans and the
pans with vials were placed in the temperature-controlled culture room. In experi-
ments in which the moths were held for more than 4 days, clean vials and saturated
cellucotton wads were provided daily.

All experiments were conducted in the same controlled temperature room at
47 4 1° C, 30-50% RH, and a daily photoperiod of 13 hr light beginning at 7:00
AM.

With all morphological drawings, a stereoscopic microscope with an eyepiece
grid was used in making measurements.

MORPHOLOGICAL STUDIES

Morphology of the Reproductive System
In order to fully understand certain aspects of mating behavior, the infernal
reproductive morphology of the lesser cornstalk borer needed examination. The
literature contains no reference to the subject. However, other workers have
examined several related species, which are compared with E. lignosellus below.

Materials and Methods

Five 1 -day-old adults of each sex were dissected in physiological saline con-
sisting of NaCI 8 gm, KCI 0.2 gm, CaCI2 0.2 gm, H20 to liter.

Results and Discussion

Male

The male reproductive systems of E. lignosellus and the phycifid species
Anagasta kuehniella (Zeller) (Mediterranean flcjr moth), Ephestia cautella (Walker)
(almond moth), Ephestia ellutella (Hubner) (tobacco moth), and Plodia interpunctella
(Hubner) (lnd;an-meal moth) (Norris, 1932) are very similar, but the ductus ejacu-
latorius simplex and cornutus of E. lignosellus differ from the others.

The unpaired ductus ejaculatorius simplex extends from the caudal end of the
ductus ejaculatorius duplex (Fig. 3, D.e.d) to the aedeagus (Fig. 3, A). In the
Noctuidae, Callahan (1958b) and Callahan and Chapin (1960) divided the duct

22

23
into a cephalad primary secretory region and a caudad cuticular region where sperma-
tophore precursors are molded. Later Callahan and Cascio (1963) divided the primary
secretory region into the 1st and 2nd secretory areas. Norris (1932) histologically
determined 4 secretory regions in the ducts of A. kuehniella, Ephestia spp. , and P.
interpunctella, while Musgrave (1937) recognized 8 regions in A. kuehniella.

In E. lignosellus, 4 regions are present in the duct, based on exterior gross
morphology (Fig. 3). They are described below using the terminology of Norris
(1932) with the terminology of Callahan and Cascio (1963) in parentheses.

The 1st region, which appears to include the 1st 3 unpaired glands, (=2nd
secretory area of the primary simplex) extends approximately 11.5 mm (diameter,
0.15 mm) from the ductus ejaculatorius duplex (Fig. 3, P.s.2).

The 2nd region or 4th unpaired gland (-1st secretory area of the primary sim-
plex) extends 2.0 mm (diameter 0.2 mm) (Fig. 3, P.s. 1). The region is not as great-
ly inflated with respect to the 1st 3 unpaired glands in A. kuehniella, Ephestia spp.,
and P. interpunctella.

The 3rd region or ductus ejaculatorius is 4 mm long (Fig. 3, D.e). The in-
flated 4th region is the bulbus ejaculatorius (=cuticular simplex) (Fig. 3, B.e). The
elongated horns of the ductus ejaculatorius of A. kuehniella, Ephestia spp., and
IP. interpunctella are replaced in E. lignosellus by 2 swollen structures in the same
position as the horns (Fig. 3, l.c), adjacent to the aedeagus (Fig. 3, A).

The cornutus of E. lignosellus is a slender curved tooth (Fig. 3, C) differing
from the thickened teeth of various shapes of A. kuehniella, Ephestia spp., and P.
interpunctella.

The morphology of the testes of E. lignosellus is the same as in A. kuehniella,

Explanation of Fig. 3

Terminology mostly after Norris (1932)
Terminology after Callahan and Cascio (1963) in parentheses

A Aedeagus

A.g Acessory glands

B.e Bulbus ejaculatorius (of cuticular simplex) of ductus ejaculatorius simplex

C Cornutus

D.e Ductus ejaculatorius of ductus ejaculatorius simplex

D.e.d Ductus ejaculatorius duplex

E Endophallus

I.C Inflated chambers of ductus ejaculatorius (of cuticular simplex) of ductus
ejaculatorius simplex

P.s. 1 (1st secretory area of the primary simplex) of ductus ejaculatorius simplex

P.s.2 (2nd secretory area of the primary simplex) of ductus ejaculatorius simplex

S.v Seminal vesicle

T Testes

V.d Vas deferens

25

Fig. 3. -Reproductive system of the male lesser cornstalk borer

26
Ephesfia spp., and P. interpunctella. Cholodkovsky (1884) recognized 4 groups of
Lepidoptera based on testes types: (A) testes completely separate and 4-lobed, as
in Hepialus; (B) testes separate but rounded and 3-lobed, as in Saturnia; (C) dis-
cernibly separate testes enclosed in a single scrotum, as in Lycaena; and (D) testes
fused and appearing as a single round organ in a common scrotum, as in Pieris. All
phycitid species previously mentioned belong to group D.

Female

The female reproductive system of E. lignosellus differs in several details from
the phycitid species by Norris (1932).

The bursa copulatrix of the lesser cornstalk borer consists of a sac, the corpus
bursae (Fig. 4, C.b), and a neck, the ductus bursae (Fig. 4, D.b), and opens ex-
ternally andventrally thru the ostium bursae (Fig. 4, O.b) on the 8th sernite. The
corpus bursae bears a large dorsal and small ventral plate bearing approximately 25
and 53 teeth or signa respectively (Fig. 4, D.p.s and V.p.s), which project into
the corpus lumen and oppose each other. In P. interpunctella, the 3-8 signa are
arranged on the dorsal wall of the corpus, while A. kuehniella has 2-4 signa on the
ventral wall only.

The ductus seminalis in E. lignosellus (Fig. 4, D.s) is of uniform diameter for
its entire length and apparently lacks a bulla seminis. The duct enters the corpus
bursae at a projection on the caudal end of the corpus. In A. kuehniella, Ephestia
spp., and P. interpunctella the duct winds around the corpus bursae in close asso-
ciation with the corpus wall and opens into the corpus adjacent to the signa, about
1/3 the corpus length from the cephalad end.

The glandula recepfaculi of E. lignosellus (Fig. 4, G.r) is an elongate simple

Explanation of Fig. 4
Terminology after Norris (1932)

A.g Accessory gland "

C Calyx

C.a.g Common duct of accessory gland

C. b Corpus bursae

Co Common oviduct

D.b Ductus bursae with longitudinally ribbed scleroiization

D.p.s Dorsal plate with signa

D.r Ductus receptaculi

D.s Ductus seminal is

G.r Glandula receptaculi

l.v Inflated part of vestibulum wall

L.a.g Lateral duct of accessory gland

L.o Lateral oviduct

M Membrane surrounding the bursae copulatrix and the ductus seminalis

O. b Ostium bursae

Ovar Ovariole

Ovip Ovipositor

R.a.g Reservoir of accessory gland

T.v Terminal vesicle

Va Vagina

Ve Vestibulum

V.p.s Ventral plate with signa

28

V.p.

Fig. 4. -Reproductive system of the female lesser cornstalk borer

29

structure tapering caudally and leading to the coiled ductus receptaculi (Fig. 4,
D.r) which in turn opens into a hemispherical inflated portion of the dorsal ves-
tibulum wall (Fig. 4, l.v). In P. interpunctella/ the gland is nearly always simple.
In A. kuehniella it is often bifurcated at the tip, and one branch may be shorter
than the other. In both species, the gland opens into a caudal sac, the recepta-
culum seminis, which leads to the ductus receptaculum.

The lesser cornstalk borer accessory glands (Fig. 4, A.g) are elongate struc-
tures leading to a series of convolutions that ultimately open into the oval-shaped
reservoirs (Fig. 4, R.a.g) which in turn open into narrow ducts leading to the
common accessory gland duct (Fig. 4, C.a.g). ln_A. kuehniella, Ephestia spp.,
and P. interpunctella, the reservoirs are elongate structures with the greater part
of the caudal lengths dilated.

The Spermatophore

During a successful mating, the Lepidoptera transfer sperm in a spermatophore
formed from secretions in the male ductus ejaculatorius simplex (Callahan, 1958b).
Even within families, the spermatophore shape varies greatly (Williams, 1941), and
formation and transfer mechanisms are sometimes highly complex (Callahan, 1958b).

A spermatophore of A. kuehniella, E. cautella, E. elutella, or P. interpunctella
consists of a rounded corpus with a narrow twisted collum ending in a frenum. Solid
horns on the frenum correspond exactly in number and arrangement with species
specific structures of the ductus ejaculatorius. The sperm escape thru an oval aper-
ture in the frenum with the aperture at the ductus seminal is entrance (Norris, 1932).

Petersen (1907) found that Lepidoptera with ductus seminalis apertures distal
on the ductus bursae produce spermatophores with long collums. Where the aperture

30
appears in the corpus bursae, collums are either short or twisted beside the sperma-
tophore corpus, as in Anagasta, Ephestia, and Plodia (Norris, 1932).

Williams (1941) divided the Heterocera into 3 groups based on spermatophore
communication in the female reproductive system: (A) spermatophores in direct
communication with the ductus seminalis, which are found in the majority of the
moths; (B) spermatophores communicating with a duct leading to a secretion filled
reservoir opening into the ductus seminalis which leads from the reservoir to the
vagina, which are found in some arctiids and tortricids; and (C) spermatophores
opening into the ductus bursae which extends to the vagina, which are found only
in the primitive prodoxids.

Stitz (1901) believed the signa punctured the spermatophore, but Williams
(1938) believed spermatophores were dissolved by enzymes in the ductus bursae.
Callahan (1958b) stated that there is no evidence for either of these beliefs. He
felt Petersen's (1907) theory that the signa serve to hold the smooth plastic-like
spermatophore in place is probably correct.

The empty spermatophores in female potato tuberworm moths, Phthorimaea
operculella (Zeller), are forced anteriorly in the corpus bursae when multiple
mating occurs (Hughes, 1967). Several are found collapsed and nested within
each other, while the most recently deposited spermatophore occupied ihe corpus
bursae posteriorly.

The purpose of this section is to present the spermatophore morphology of E.
lignosellus, its position in the corpus bursae, the probable mode of sperm escape
from the spermatophore, and the fate of empty spermatophores.

31

Materials and Methods

Five spermatophores representing 1st matings by both males and females were
dissected from females and placed in physiological saline. During dissections, the
spermatophore orientation in the corpus bursae was observed.

The spermatophores in multiple mated females were observed in moths taken
from 4 mating-oviposition cages. Thirty-two females had 2-5 spermatophores in
the corpus bursae.

Results and Discussion

The spermatophore is illustrated in Fig. 5. The frenum bears 2 small rounded
projections that seem to correspond to the inflated chambers on the male ductus
ejaculatorius (Fig. 3, l.c). The aperture thru which sperm escape is terminal and
between the 2 rounded projections.

The 2 toothed plates of the corpus bursae walls tightly hold the spermatophore
in place. The collum is twisted and pressed against the posterior lateral wall of
the corpus bursae, and the frenum with its aperture is in direct contact with the
ductus seminalis. Thus the lesser cornstalk borer belongs to Williams' (1941) group
A.

As in the potato tuberworm moth (Hughes, 1967), when multiple mating occurs,
empty spermatophores are forced anteriorly in the corpus bursae flattening ana/or
nesting into one another. The most recently deposited spermatophore is held tightly
between the 2 plates of signa, which seems to support Petersen's (1907) theory of
signa function. No spermatophores were punctured and none showed evidence of
being dissolved. Callahan (1958b) found striated muscle tissue surrounding the
corpus bursae wall of Heliothis zea (Boddie) and theorized constriction of the muscle

32

Corpus

Collum
Terminal aperture

Rounded projection
Frenum

Fig. 5.-Spermatophore of the lesser cornstalk borer

33

exerted pressure on the spermatophore corpus, thereby forcing sperm out of the struc-
ture. This may be the mode of sperm escape from lesser cornstalk borer spermato-
phores.

Primary Simplex and Spermatophore Color
Snow and Carlysle (1967) reported that the 1st secretory area of the primary
simplex in a virgin male fall army worm, Spodoptera frugiperda (J. E. Smith), Is
filled with a light brown to black fluid. During mating, portions of the pigment are
passed to the female corpus bursae, while the remainder is incorporated into the
spermatophore, resulting in a darkly pigmented spermatophore. The simplex is left
transparent and colorless-to-yellow. A darkly pigmented spermatophore and a trans-
parent, colorless-to-yeilow simplex together indicate a 1st mating for the male.
Subsequent spermatophores are clear to yellow.

The technique is limited by age. Newly emerged males have light to medium
brown pigment in the simplex. Males mating once and retained 4 days after removal
of females have transparent, yellow, or light brown pigment. Virgins of this age
have dark brown to black pigment in the simplex and hence are distinguishable from
mated males.

The purpose of this experiment was to determine if a color change of the primary
simplex fluid indicates a male has mated within 24 hr, and if so, how long the re-
sulting color is retained. Spermatophore color was checked to see if those passed
1st differed from those passed subsequently.

Materials and Methods

Each of 182 3-day-old males were caged with two 3-day-old females for 1

34
day. The females were dissected for sperrnatophores. Males were dissecfed for de-
termination of simplex color in the morning, afternoon, or evening.

The above experiment indicated virgin males tend to have translucent yellow
simplex fluid, while mated males had transparent, colorless-to-yellow fluid. To
test this further the following experiments were conducted.

Twenty-five each of 1-, 2-, and 3-day-old virgin males and 10 each of 4-,
5-, and 6-day-old virgin males were dissected for determination of simplex fluid
color and light transmission.

Thirty 1-day-old virgin males were caged individually with two 1-3-day-old
virgin females for 1 day. Females were dissected for sperrnatophores. Ten mated
males were retained 2, 4, and 5 days after removal of females. Five males of each
group were dissected for determination of simplex fluid color and light transmission
between 9-11 AM and 5 were dissected between 9:30-11 PM.

Ten 1-day-old virgin males were individually caged with two 1-3-day-old
virgin females. Females were replaced daily by two 1- to 3-day-old virgin fe-
males for 3 days. Females were dissected for sperrnatophores and the color of 1st
and subsequent sperrnatophores was compared. Five males were dissected for de-
termination of simplex fluid color and light transmission at 1 1 AM and 5 at 9:30
PM.

Materials and methods for further data on simplex color and light transmission
and spermatophore color are presented in the section below dealing with mating
behavior.

Results and Discussion

Table 3 indicates a progressive color change in simplex fluid color of 3-day-old

35
males within 24 hr after mating. All spermatophores were clear and transparent.

Simplex fluid color was translucent cream-yellow to yellow in 1- to 3-day-
old virgin males and trcnslucent yellow in virgin 4- to 6-day-old males.

All mated males retained for 2, 4, and 5 days after removal of females had
transparent yellow simplex fluid. Six males not mating the day of caging had
translucent yellow fluid the following day.

Nine males mated on each of 3 days when caged with females 3 days. Four
males dissected in the morning had transparent colorless simplex fluid. One male
failed to mate the 3rd night and had transparent pale yellow simplex fluid. All
males dissected in the evening had transparent pale yellow simplex fluid. All
spermatophores passed on the 3 nights were clear and transparent.

The above indicates that mated males can be distinguished from virgin males
by transparent versus translucent simplex fluid for at least 5 days after mating. A
mating during the previous night is indicated by transparent colorless simplex fluid.
Color of 1st, 2nd, and 3rd spermatophores passed successively on 3 nights is iden-
tical and does not distinguish between 1st and subsequent matings.

Data from the section below dealing with mating behavior indicated the pri-
mary simplex fluid of 1-day-old males was colorless and transparent in all mated
males and translucent yellow in 2 unmated males. Apparently 1-day-old meted
males can be distinguished from unrnated males of the same age within 3 hr of mating.

Egg Development and Position Relative to Age
The Lepidoptera show considerable variation in egg development at emergence.
Eidmann (1931) placed the Lepidoptera in 3 groups based on the number of full-
sized eggs in the ovaries at adult emergence: (A) species with very few full-sized

36

Table 3. -Color of fluid in the 1st secretory area of the primary simplex of

3-day-old mated and unmated lesser cornstalk borer males at different

periods of the day following mating the previous night.

Mated Males Unmated Males

Color of simplex (%)
low

Time of

Sample

Col

or of :

iimplex (%)

dissection

Size

Clear

Pale

-yellow

7-12 AM

51

84

2- 3 PM

21

57

5

7- 9 PM

46

33

35

9-11 PM

64

50

Yellow Pale-yellow Yell

16

38

8 2 22

23 27

37

eggs at emergence, typical of butterflies and moths with a long adult life; (B)
species having a 2-or 3-fold increase in full-sized eggs in the imago, as with most
Heterocera; and (C) species with all eggs fully developed at emergence, as in the
Bombycidae and Lymantriidae,

Full-sized eggs are present in ovaries of newly emerged A. kuehniella fe-
males, but none are present in P. interpunctella females at emergence (Norris,
1932).

The purpose of this experiment was to determine the stage of egg development
and egg position in the reproductive tract of virgin females relative to age.

Materials and Methods

Moths 0-8 hr old and 1 and 2 days old were retained individually in 4-dr
vials until dissected in distilled water. Moths were classified into 4 groups; (A)
moths with full-sized eggs in the common oviduct, lateral oviducts, calyx, and
ovarioles; (B) moths with full-sized eggs in the lateral oviducts, calyx, and
ovarioles only; (C) moths with full-sized eggs in the calyx and ovarioles only;
and (D) moths with no full-sized eggs. The number of visible eggs in the ovarioles
of 0-8-hr-old females were recorded.

Results and Discussion

No full-sized eggs were present in 0-8-hr-old females (Fig. 6) which would
place the lesser cornstalk borer in Eidmann's (1931) group A. However, the moth's
life span is relatively short (8-22 days) under outside conditions (Dupree, 1965;
Leuck, 1966). An average of 26 eggs were visible per ovariole.

Unlike H_. zea (Callahan, 1958b), some E. lignosellus virgin 1-day-old females

38

N =

100

23

90

_

80

-

70

-

60

50

40

-

30

-

20

10

-

0

0-8 hr

N=
56

1 day
Age

2 dQN

| Group A. Full-sized eggs In common oviduct, lateral
oviducts, calyx, and ovarioles

\Ua Group B. Full-sized eggs in lateral oviducts, calyx,
and ovarioles only

b^j Group C. Full-sized eggs in calyx and ovarioles only
[ I Group D. No full-sized eggs

Fig. 6. -Egg development and position in reproductive tract of lesser cornstalk
borer virgin females relative to age

39

developed full-sized eggs which appeared in the common oviduct, lateral oviducts,
ana/or calyx (Fig. 6).

Morphology of the Tympanic Organ
The lesser cornstalk borer has tympanic organs. Thoracic and abdominal
tympanic organs are found in 11 families of Lepidoptera within the Noctuoidea,
the Geometroidea, and the Pyraloidea. As far as known, they are lacking in all
other groups (Bourgogne, 1951). The thoracic type is confined to the Noctuoidea,
and is considered monophyletic by Kiriakoff (1963). The abdominal organs are
divided into 3 groups and appear on the 1st or 2nd segments in the Pyraloidea,
the Geometroidea, and the Drepanoidea. The abdominal types ere poorly known
but appear polyphyletic in origin. Eggers (1919, 1925, 1928) and Kennel and
Eggers (1933) published extensive works on the abdominal organs, but in recent
years, these organs have been ignored (Kiriakoff, 1963).

In the Pyraloidea, tympanic organs are found in the 1st abdominal segment,
and are often obscure externally since the tympani face the thorax (Bourgogne,
1951). Tympanal cavities are shallow or essentially absent. Principal tympani
are situated ventral!-/ on the modified anterior portion of the 1st abdominal ster-
nites (sternites 1 and 2), and are separated by a strongly scaled and sclerified
longitudinal band. The band frequently continues posteriorly in 2 large projecting
lobes that sometimes serve as tympanal opercula. Each tympanic organ has a
tympanal sac enclosed in a chitinous hemisphere formed by integumental invagi-
nation. Its walls are formed by 2 lamellae which remain completely separated, or
may be partly or completely closed. The scolophore (=scolopophorous organ), con-
taining 4 scolopalia, may extend from the tympanum to the hemisphere surface

40
or to an internal ridge. In some subfamilies, as many as 5 accessory tympani may
be present: (A) a single dorsal tympanum composed of a thin metapostnotal ridge;
(B) a pair of lateral tympani on the metathoracic epimera or on either side of the
metapostnofum; and (C) a pair of coxal tympani on the posterior face of the meta-
thoracic coxae.

Materials and Methods

Five 1-day-old adults of each sex were dissected in distilled water. The
thorax was separated from the abdomen, and the 1st abdominal segment bearing
the tympanic organs was separated from the remaining abdominal segments. This
permitted an unobstructed view of the anterior surfaces. To expose internal struc-
ture, an incision was made just posterior and lateral to the anterior margin of the
right organ.

Results and Discussion

Figs. 7 and 8 illustrate the external and internal structure of the organs.

There is no sexual dimorphism in the organ structure. The tympanal cavity
is essentially absent since only narrow ridges (Fig. 7, S.r) circumscribe the
anterior surface of the 1st abdominal segment. The tympanal sacs (Fig. 8) and
tympani (Fig. 7, T) are separated by a strongly scaled and sclerified longitudinal
band (Fig. 7, S.l.b) which terminates ventral to the oriface thru which the internal
organs pass (Fig. 7, O). The metathoracic coxae and the scales on the longi-
tudinal band obscure the tympanal surface externally. The principle tympani are
ventrally located, and the presumed scolopophorous organs, easily seen thru the
thin tympanal integument, pass ventrally from the tympanic surface to an internal

41

ridge (Fig. 8) which leads to the mesal surface of the tympanal sac. Two com-
pletely separate lamellae form the tympanal sac wall. Integumentary folds possi-
bly formed from the metathoracic epimera overlap the tympanic surfaces and form
presumed accessory tympani (Fig. 7, A.t).

The tympanic organ structures of E. lignosellus agree with the general
pyraloid described above.

Explanation of Fig. 7

A.t Accessory tympanum

O Orifice for internal organs

T Tympanum

S.r Sclerotized ridge

S.o Scolophophorous organ

S.l.b Sclerotized longitudinal band

43

7. -External anterior view of the first abdominal segment of the lesser
cornstalk borer moth illustrating the tympanic organs on the excised
abdomen

44

Tympanum

Ridge on tympanal sac wall

Tympanal sac
Scolopophorous organ

.5

Fig. 8-lnternal lateral view of the right tympanic organ of the

lesser cornstalk borer with the lateral wall of the tympanal
sac removed

BEHAVIORAL STUDIES

Mating Cage Conditions

Workers used various mating cage conditions. Luginbil! and Ainsiie (19] 7) used
glass lantern chimneys of unspecified size in mating and oviposition studies with single
pairs. They stated that fed moths lived longer than starved, but did not distinguish
between the 2 groups in their data. Dupree (1965) mated pairs of moths in 30 x 100
mm shell vials with about 30.0 cc/moth, and fed them honey diluted with 1 part
water adding sodium benzoate to prevent spoilage. Leuck (1966) retained an un-
specified number of moths in a 1 cu ft polyethylene covered mating cage, and fed
them 10% honey-water. Calvo (1966) retained 35 moths of each sex in a screen cage
with 113.8 cc/moth. No mating occurred unless there were 5 moths of each sex per
cu ft. Stone (1968) used 10 moths of each sex per mating-oviposition cage with 30.3
cc/moth. Both Calvo and Stone fed moths 2% sucrose solution.

The purpose of this experiment was to find a convenient cage size with accept-
able top material and cage placement for mating behavior studies, and to determine
if fed and unfed moths mated with equal frequency.

Materials and Methods

Vials of 4- and 40-dr were tested as mating cages. In each of ten 4-dr vials,
1 pair of 1 -day-old (0-24 hr) moths and a cotton wad were placed. The cotton wads

45

46
were left dry in 5 vials and saturated with 2% sucrose solution in 5 vials. Satu-
rated cotton wads were resaturated when nearly dry. All vials were stoppered
with cotton plugs, placed horizontally, and held for 6 days. Further tests with
fed moths in 4-dr vials involved 6 pairs of 1-day-old moths for 5 days, 4 pairs of
2-day-oId moths for 7 days, and 4 pairs of 3-day-old moths for 7 days.

In the 40-dr vials, mating frequency of fed versus unfed moths was com-
pared. In addition, screen versus cellucotton tops and vertical versus horizontal
vial placement were tested concurrently using a series of 176 vials. The influ-
ence of water versus the 2% sucrose solution on mating frequency was not tested.
In each of the 176 vials, 1 pair of 2-day-old moths was held 4 days. In 88 of
these vials, the cotton wad was saturated with 2% sucrose solution, in the other
83 vials they were left dry. Forty-four of each set of 88 were closed with squares
of 14 x 18 mesh/in fiberglas screen held in place with rubber bands, while the
other 44 v/ere closed with squares of celiucotton 1/2 rnm thick held in place with
rubber bands. Lastly, each set of 44 vials was again divided with 22 held verti-
cally and 22 held horizontally.

At the end of each test, females were dissected for spermatcphores.

Results and Discussion

No mating occurred in 4-dr vials, where available space was 7.2 cc/moth.
Under fed versus unfed conditions, 1 fed female, 3 unfed males, and 1 unfed
female died.

Mating occurred in the 40-dr vials, where available space was 29.5 cc/moth
(Table 4). Chi square analysis of the multiple factor test indicated no significant
difference at the 1% level among position, cage top material, and fed versus

47

Tabie 4. -Cage conditions and spermatophores passed by 2-day-old fed and unfed
lesser cornstalk borer adults, tested for 4 days in 40-dr vials, 1 pair per vial, 22
replicates per test.

Conditions

No.
moths
dead

Cages
without
mating

Cages

with 1 or

mere sprmts.

Multiple

matings

sprmts. cages

Total

sprmts.
passed

Fed (2%

sucrose)

Screen top,

0

10

12

2

2

20

vertical

4

2

Screen top,

l$ma(2)b

10

12

2

5

19

horizontal

3

1

Cellu. top,

0

6

16

2

4

27

vertical

3

4

2

1

Cellu. top,

0

8

14

2

5

22

horizontal

4

1

Screen top,

8 66

vertical

19(0)'

Screen top,

10 66

horizontal

Cellu. top,

6dc5

vertical

Cellu. top,

5 66

horizontal

Unfed (No sucrose)
12 10

10

12

mates attached when cage dismantled
number of spermatophores accepted

12

16

10

2 2

2 1

12

12

16

48
unfed moths for a single mating per pair. Fed moths had highly significantly more
multiple matings than unfed moths. Twenty-nine unfed males died while no fed
males died during the tests.

Forty-dr vials were thus considered adequate for mating studies. Moths should
be given sugar solution to avoid death within 4 days if the moths are retained for
several days, or if multiple matings are desirable.

Mating Behavior

The mating behavior of the lesser cornstalk borer has not been reported in the
literature. Luginbill and Ainslie (1917) assumed mating occurred the 2nd night
after emergence. Leuck (1966) stated that moths were most active in the field
after dark in still air with low humidity at temperatures exceeding 80 F. He felt
these conditions were optimum for mating and oviposition.

A. kuehniella and P. interpunctella females "call" prior to mating, that is,
the abdomen is bent dorsally between the wings and the ovipositor is alternately
protruded and retracted. Calling by P. interpunctella females is not correlated
with egg development since it occurs before and after full- sized eggs are pre-
sent, and after all eggs are laid (Norris, 1932).

Richards and Thomson (1932) reported mating behavior in a general discussion
of the genera Ephestia, Anagcsta, and Plodia, but made no reference to behavior
of a given species. Receptive females begin calling with the apical half of the
abdomen bent dorsally between the wings. The ovipositor is alternately protruded
and retracted. A male begins fluttering around the female which does not respond
or runs away. Eventually the female stops, the male faces her head to head and
bends his abdomen dorsally and anteriorly to grip the female abdomen tip. Quickly

49
the pair twists around and assumes an end to end copulatory position.

Williams (193S) stated that the A. kuehniella female calls with the wings
spread and the abdomen curved upward until mating occurs. Females are quiet
(=stationary?) when calling. The male moves about vibrating his wings until he
meets a female. He then curls his abdomen towards her and couples.

Schwink (1953) reported that A. kuehniella and P. interpunctella males re-
spond to their respective females with long-lasting whirrings. Whirs lasting 40
sec to several minutes are separated by short pauses and occur many times within
several hours.

Brindley (1930) stated that copulation of A. kuehniella occurs after midnight
the day of emergence, and lasts 4-6 hr. Norris (1932) reported that copulatory
duration of A. kuehniella is 3-4 hr, and 1-1 1/2 hr for P. interpunctella. Williams
(1938) reported that copulation lasts 3-5 hr for A. kuehniella.

The purpose of this experiment was to observe pair formation and courtship of
E. lignosellus, time of coupling, duration of copulation, uncoupling of mates, and
post copulatory activity. In addition the following factors were observed: number
of spermatophores passed per mating; and egg development and plccement of full-
sized eggs in the reproductive tract of mated and unmated females.

Materials and Methods

Pairs of 1 -day-old moths were placed in each of 5 clear plastic containers,
12 1/4 cm x 17 1/4 cm x 6 cm deep. Cellucotton squares, 3 mm thick and 4 cm
on a side, were folded in 3rds, saturated with 2% sucrose solution, and placed in
the left back corner of the cage floors. The cage mouths were covered with 2-mm-
thick cellucotton held to the uppermost cage perimeters with rubber bands to permit

50
maximum visibility. Cages were set on platforms composed of 2 containers, iden-
tical to the cage, stacked on top of each other and separated from other platforms
by 28 cm. One ft behind each cage was a 7 1/2 watt red light with a reflector
which illuminated the cages at about 1 ft-candle. The main lights were turned out
and the red lights turned on at 8:00 PM.

The laboratory temperature during experimentation was 45.5 4- 3° C both
nights. The 1st night, the relative humidity control was turned to capacity at
8:00 PM and turned off at midnight. Before the experiment, humidify was 46%
RH, at midnight 70 4- 4%, and at 8:00 AM 46 + 5% RH. The 2nd night, humidity
was 46 4- 5%RH.

Five pairs of moths were observed each of 2 nights, from 8:00 PM to 1 1:00
PM at 15 min intervals, and continuously from 11:00 PM to 6:40 AM the 1st night,
and from 1 1:00 PM to 5:20 AM the 2nd night. Thereafter, observations were made
every 5-40 min until 8:06 AM the 1st night and 6:45 AM the 2nd night. During
breaks between the final observations, females were dissected for spermatophores
and for observations of egg development and placement in the reproductive system.
Males were dissected and the color of the 1st secretory area of the primary simplex
recorded; these results are reported in the section above dealing with primary sim-
plex and spermatophore color.

Results and Discussion

Until midnight the moths remained still or ran and/or flew about the cage with
no seeming orientation to each other. If a pair met, they avoided each other by
turning aside or dropping to the cage floor. Females were generally more active
than males up to midnight, in contrast to daylight hours when the reverse is true,

51

as seen in mating-oviposition cages in the culture room and in handling moths in
other experiments.

In the description below, "calling" by females refers to a posture in which the
abdominal tip is thrust between and above the wings, and the ovipositor is inter-
mittently protruded and retracted. "Whirring" by males refers to the wings raised
vertically over the thoracic dorsum, and forming a blur describing arcs of an esti-
mated 30°. At the same time, the abdomen is raised dorsal ly with the tip between
the wings, except immediately before attempted coupling.

The female initiates pair formation by calling as she remains stationary on the
horizontal lower surface of the cellucotton cage top or on the vertical cage side.
The male begins vibrating his antennae up and down asynchronously, makes a circle
in place, and approaches the female with his wings slightly parted. If the male
approaches the female from behind, he flails her abdomen tip with his antennae,
the female makes a half circle in place, and the moths flail each others' antennae
head to head. If on the other hand the male approaches the female head to head,
the moths flail each others' antennae. The male then whirs his wings. The female
may make no, 1 , or several circles in place. The moths continue flailing each
others' antennae if the female does not circle, or the male flails her body with his
antennae if she circles. During this time the male continues bursts of whirring,
separated by brief pauses. With the female facing the male, the male continuously
whirs his wings as he curls his raised abdomen with claspers extended towards the
female, quickly twists toward her right or left, and strikes at her abdomen tip. If
coupling is successful, the male stops whirring and pivots in a half circle as the
female pivots slightly placing the body axes in a straight line, end to end, flat to

52

the surface. If the pair fails to couple, the female continues calling while the
male pauses, the moths flail each others1 antennae, and the male whirs continuous-
ly as he strikes again. This procedure is repeated 3-5 times until coupling occurs
or the female walks away. After coupling and pivoting to the end-to-end position,
the pair remains stationary and oppressed to the surface.

Uncoupling begins with the mates gradually raising the abdomens to form a
130-140 angle to each other. The male pumps his abdomen, finally raises his
wings several times, and sometimes vibrates them briefly. The female may pump
her abdomen as she grasps the surface. The pair may turn a half circle end back
again while pulling alternately, or the male may turn about 40 and then back
again. The male abdomen may be bent into a vertical "S" shape during this process
or remain straight but raised vertically. The mates ultimately uncouple either from
a straight line position or at a 140 angle to each other laterally.

After uncoupling, the mates tend to be active for 5-10 min moving about the
cage and feeding, but finally settle down for the rest of the night.

Eight of the 10 pairs mated. Calling occurred from 1:15 AM to 6:40 AM the
1st night, and from 1:45 AM until continuous observation was terminated (6:45 AM)
the 2nd night. Of 73 callings recorded, 19 initiated courtship, i.e., the attracted
males whirred at least once next to the females. Of the 19 courtships, 7 led to
coupling. In addition, 12 courtships occurred with females not observed calling
immediately prior to courtship. However, half of these were in a single cage that
was not observed as closely as the other cages, and calling could have occurred.
In addition, courtship was sometimes initiated within minutes after calling began,
and could easily be missed. Accepting these possibilities, apparently only calling

53

females attract males.

In 4 matings, females called only once during the night, from 1/2 to 5 min,
and were coupled within 1-7 min after initiating calling. Two other females
called intermittently over periods of 100 and 47 min in intervals lasting 2-54 min
and 2-8 min, respectively, before coupling. The 1st was courted only once while
the 2nd was courted 4 times, once before she was observed calling during the
night, and 3 times when she called.

The pair formation and courtship behavior of E. lignosellus include activities
suggestive of olfactory stimuli. Norris (1933) stated calling P. interpunctella fe-
males stretch the intersegmental membrane bearing secretory tissue near the ductus
bursae orifice. P. interpunctella males become highly excited in the presence of
calling females, but never become sexually excited in the presence of non-calling
females (Norris, 1933; Barth, 1937). Dickens (1936) described scent scales aris-
ing from glandular areas on the 8th abdominal segment of A. kuehniella, E. cautella,
E. elutella, and F\ interpunctella. Females of all 4 species had glandular inter-
segmental folds between the 8th and 9th segments. E. cautella females also have
2 internal odoriferous glands which open into the oviduct near the genital pore.
Gotz (1951) stated female calling in Lepidoptera exposes glands secreting sex phero-
mones. Evidence does not contradict that E. lignosellus males court and couple
with females that are calling. Barth (1937) stated glands of E. elutella males se-
crete an odorous substance that increases female excitement in copulation. Vibra-
tion of the wings disperses the odor. Courting E. lignosellus males whir with the
abdomen tip, with claspers extended, held between the wings.

Coupling of E. lignosellus occurred from 1:40 AM to 6:40 AM with 7 of the 8

54
couplings occurring by 4:40 AM. Average time in copulo was 102 min (range 81-
134) including 5-10 min for uncoupling.

In unmared females, the membranous portions of the corpus bursae wall were
pressed together and no visible fluid was present within the bursae. All mated
females had a greenish fluid in the corpus bursae anterior to the spermatophore.
Not more than 1 spermatophore was passed per mating.

Among mated females, 3 had full-sized eggs in the common and lateral ovi-
ducts, 4 had full-sized eggs in the lateral oviducts but not in the common oviduct,
and 1 had only immature eggs, located in the ovarioles. The 2 unmaied females
had full-sized eggs in the lateral oviducts but not in the common oviduct. It
appears E. lignosellus females, like P. interpunctella (Norris, 1932) mate without
regard to egg development.

Influence of Additional Females on Male Mating Frequency
The presence of receptive moths was an important factor in mating studies.
Mating cage sizes used by Luginbill and Ainslie (1917), Dupree (1965), Leuck
(1966), Calvo (1966) and Stone were summarized in the preceding experiment.
Mating occurred in all cages except 4-dr vials used by Stone. Pairs of moths
mated in 40-dr vials, but to assure that receptive females were present for test
males in other experiments, I decided that greater female numbers per cage
might be desirable. The purpose of this experiment was to determine if additional
females per male influenced mating frequency.

Materials and Methods

Tv/o-day-old males and females were caged in 40-dr vials for 1 day using

55
the following numbers of individuals, male:females, with the space available per
moth in each case: 1:1, 73.5 cc; 1:2, 49.0 cc; 1:3, 36.8 cc; 1:4, 25.4 cc. Equal
numbers of each ratio were run on a given day until the ratios were replicated 100
times. At the end of each test, females were dissected for spcrmatophores.

Results and Discussion

Males mated with approximately equal frequency at all 4 ratios: 1:1, 60%;
1:2, 61%, 1:3, 75%; 1:4, 70%. Chi square analysis indicated no significant
differences at the 5% level. Either the lack of successful mating is principally
attributable to the male or else additional females resulted in inhibiting factors
approximately equal to the increased probability that at least 1 female would be
receptive. Not more than 1 spermatophore was passed per night per male.

Influence of Age on Mating
There is much variation in the Lepidoptera as to age of mating. Richards
and Thomson (1932) found that moths of the genera Ephestia and Plodia adults are
ready to mate soon after emergence, almost as soon as the wings are dry. The
corn earworm, H. zea, never copulates the 1st night after emergence or on the
emergence night, and all copulations occur between the 2nd and 7th complete
nights after emergence (Callahan, 1958a). The cabbage looper, Trichoplusia ni
(Mubner), most frequently mates the 2nd and 3rd nights after emergence. Males
never mate on the 1st night after emergence, but a small percentage (7%) of fe-
males mated the 1st night (Shorey, 1964). However, Henneberry and Kishaba
(1967) reported male cabbage loopers mated infrequently the 1st night after emer-
gence and most frequently the 3rd and 4th nights after emergence. The pink

56

boilworm, Pectinophora gossypiella (Saunders), mates most frequently at ages 5-6
days (Ouye etal., 1964). The oriental fruit moth, Grapholitha molesta (Busck),
mates within 24 hr of emergence, and males mate daily during the 1st 7 days after
emergence (Dustan, 1964). The granulate cutworm moth female, Feltia subterranea
(F.), mates most frequently the 3rd night after eclosion (Cline, 1967).

The purpose of this experiment was to determine the influence of age on mat-
ing of 1-6-day-old lesser cornstalk borer males and females.

Materials and Methods

Moths 1-6 days old were tested at 1 maie:4 females and vice versa for 1
day. All combinations of ages and both sex ratios were replicated 5 times each,
making a total of 360 test cages. At the end of each test, females were dissected
for spermatophores.

Results and Discussion

The data were pooled as indicated in Fig. 9. The overall average for the
experiment was computed since mating frequency under the 4 conditions plotted in
Fig. 9 was essentially the same (average 61%, range 60-62%). Mating frequency
of each age group was compared with the overall average using a 2-failed "t" test.

None of the 24 mating frequencies were significantly different from the over-
all average at the 1% level. Thus the lesser cornstalk borer mates equally well at
age 1-6 days under the above conditions.

Influence of Male Antennectomy on Mating
Defhier (1953), Schneider (1964), and Jacobson (1965) include many re-
ferences establishing the antennae of insects as the principal site of olfactory

0 O

1 Ov

57

D

2 o

0) I

O) o

O ^

E g>

.9 9

o
Q

^o

LO

1

^r

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CM

1

1

-

1 1 1 1 1 1

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o "5

o >o

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4)

-o i

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E O

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£ s

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58
receptors. This may explain why male moths deprived of their antennae or having
antennae coated with various substances either do not mate or mate infrequently.

The purpose of this experiment was to determine the influence of bilateral
antennectomy of the male on mating.

Materials and Methods

Two 2-day-old females were caged with two 2-day-old males handled in 1
of 3 ways. Group A males were caged untreated. Group B males were knocked
down by a 5 sec exposure to COo and the left meso- and right metathorccic legs
were excised between the thorax and the coxae. Group C males were also knock-
ed down with CO2 as in Group B and both antennae were excised between the
head and the scape. All excisions were done with the aid of a microscope.

Groups were run concurrently and replicated 25 times. Cages were retained
2 days.

Results and Discussion

In Group A, 47 spermatophores were passed, in Group B, 43, and in Group
C, 1.

Complete bilateral antennectomy inhibits mating of E. lignosellus males.
Based on behavior of other Lepidoptera, this is possibly due to removal of olfactory
receptors which trigger pair formation, courtship, and mating on reception of the
female sex arrractant.

Longevity of Virgin and Mated Moths, Sperrnatophore Passage and Acceptance,
and Fecundity

The purpose of this research was to determine the longevity of virgin and
mated moths, male and female mating frequency, the number of eggs laid per

59
mated female, and the temporal oviposition pattern during the total oviposition
period of mated females.

Materials and Methods

Twenty-five each virgin males and females were retained for life. Newly
emerged moths were placed singly in 40-dr vials and assigned an identification
number. Four to 8 moths of the same sex were caged as available on a given date.
Males were caged on 5 days, every 3rd day, and females were caged on 4 days,
2, 6, and 5 days apart.

Newly emerged moths used concurrently for longevity, mating frequency,
and fecundity records were placed in 40-dr vials and assigned an identification
number. Three 1- to 3-day-old virgin moths of the opposite sex were placed in
each vial and were replaced daily for the life of the retained moths. As the re-
tained moths died, they were replaced until 25 of each sex were tested. Dead
retained mated females were dissected for spermatophores and retained eggs. A
moth was considered dead when it failed to move appendages or pump the abdomen
when gently probed. Females caged with single retained males were dissected for
spermatophcres when replaced by virgin females.

The research was conducted from January to March, 1967. On 10 February,
cotton wads were replaced by cellucotton wads in the 40-dr vials, since older
moths tended to entangle themselves in the cotton fibers. To statistically examine
the influence of this change, using analysis of variance, all retained mated moths
dying prior to the change and exposed to no more than 6 days to cellucotton wads
were assigned to group 1. Males with identification numbers 1-14 (excluding male
no. 11 which was exposed to cellucotton wads for 11 days) and females no. 1-6

60
(excluding female no. 4 which was exposed to cotton wads for 7 days) were in group
1. All other moths were in group 2 except male no. 11 and female no. 4.

Since nearly all virgin moths survived beyond 10 February, moths were assign-
ed to groups based on the dates they were initiated in the experiment. Longevity,
spermatophores passed or accepted, total, viable, and sterile eggs laid, number of
eggs retained at death, length of oviposition period, and longevity alone were
checked statistically using correlation coefficients for mated and virgin moths,
respectively.

Eggs laid by retained mated females on the cellucotton tops, vial sides and
bottoms, were set aside for 24 hr before counting fertile and sterile eggs. Fertile
eggs turn from cream white to red, while sterile eggs remain cream colored or turn
red at one end only.

Results and Discussion

Differences in longevity and fecundity when compared with other workers
(Tables 5 end 7) may result from rearing history, summarized under rearing proce-
dures above, meihods of handling adults, and genetic differences. Luginbill and
Ainslie (1917), Dupree (1965), and Leuck (1966) retained adults in unregulated
rooms or ouidoor screened insecfaries, while Calvo (1966) maintained adults at
constant temperatures and humidities. Sanchez (1960) worked with laboratory in-
sects at unspecified conditions, except for a few observations discussed below.
King et al. (1961) did not indicate what conditions were involved with his data.
At the time of experimentation, my colony had passed thru 7 generations. Thus
the genetic pool may have changed from that of the original stock that Calvo (1966)
used and influenced the results.

61

Tcble 5. -Longevity of lesser cornstalk borer adults.

Reference

Sex

Sample
Size

Fed

Days life

and State

Mean4-SE

Range

Median

Stone. Fla.

ma<$

25

2% sucrose

24.2-1-1.5

13-46

24

vbd

25

»

42.44-1.7

25-64

42

m 2

25

ii

18.14-1.7

12-31

17

v 2

25

n

37.6+1.8

22-55

35

Luginbill &

<5

7

some fed sugar

12.1+0.5

7-18

10

Ainslie. 1917.

sirup

Fla. &S.C.

2

7

ii

12.7+1.8

5-18

13

Sanchez. 1960. 6* 12 ? 7.5+0.3 4-12 6.5

Texas 2 7 ? 7.1+0.5 4-16 6

KingetaL 6 & 2 ? ? 8 4-19

1961. Texas

Dupree. 1965. rncJ 17c(1957) dilute honey & 11.4
Ga. mo* (1958) sodium benzoate 17.9

m2 1 7C ( 1 957)
m2 (1958)

Leuck. 1966. v <5 ? 10% honey

Ga. m$ ? "

v 2 ?

11.4

2-23

17.9

11-23

14.5

3-26

19.5

7-33

22.2+1.3

3-29

10.3+0.7

4-16

21.4+3.6

10-31

a mated

b

virgin
c Dupree used at least 17 pairs in 1957-1958 combined.

62

Longevity of individual mated males and females are shown in Figs. 10 and 11,
respectively. Males exposed to cotton wads lived an average of 4.0 days shorter
and females lived 2.5 days shorter than moths exposed to cellucotton wads. How-
ever, these differences were not statistically significant.

Mated males lived an average of 12.7 days (range 5-23) after passing the last
spermatophore (Fig. 10). Males no. 17 and 20 are not included in the average
since male no. 17 may have died prematurely in copulo and male no. 20 failed to
pass a spermatophore. Mated females lived an average of 4.7 days (range 1-13,
median 4) after the last oviposition day. Virgin females lived roughly twice as
long as mated females, thus agreeing with Leuck's data (1966) (Table 5).

Callahan (1958a) concluded that once a corn earworm moth mates, it be-
comes less active than a virgin moth and hence lives longer on the average than a
virgin. However, virgins held in holders for life lived longer than mated moths.
He acknowledged his conclusion did not seem to hold for E. kuehniella (Zeller).
The adults do not ordinarily feed and virgins possibly live longer by absorbing
retained eggs.

Norris (1933) indicated that unfed virgin E. kuehniella females lived as long
as mated females fed sugaF solution. Perhaps virgin femaies might live longer than
mated females if fed, as was the case for E„ lignosellus. Feeding versus starvation
is probably the decisive factor in E. lignosellus longevity, not degrees of activity
at least in males, as seen in 29 deaths of mated unfed males in the mating cage
conditions experiment versus no deaths of mated fed males.

Spermatophore passage and acceptance results are shown and compared with
other species in Table 6. Figures 10 and 1 1 show spermatophore passage patterns.

63

Table 6.-Spermatophore passage and acceptance during the lifetime of
various Lepidoptera

Individuals

Reference

Scientific and
common name

Sex

Mean
+ SE

Range

per mating
cage

66 : 99

Shorey et al.

Trichoplusia ni

9.

2.0

0-6

?

1962.

Cabbage looper

Shorey. 1964.

ii

6

2.0

0-10

1:2

Dustan. 1964.

Grapholitha molesta
Oriental fruit moth

2

1.5

1-4

20:20 &
25:25

Ouye et al.

Pectincphora gossypiella

<5

4.2

0-10

l:3a

1965.

Pink boolv/orm

2

2.3

0-8

6:lab

Cline. 1967.

Feltia subterranea
Granulate cutworm moth

6*

4.9

0-8

1:3

Henneberry &

Trichoplusia ni

9

1.2-1.4

?

3:3

Kishaba. 1967.°

Hughes. 1967.

Phthorimaea operculella

6

4.24-0.3

1-10

1:2

Potato tuber moth

9

2.64-0.2

1-6

2:1

Stone

Elasmopalpus lignosellus

6

7.2+0.8

0-14

1:3

Lesser cornstalk borer

2

1.7+0.2

1-3

3:1

Three virgin moths age 2-5 days, and virgins no more than 2 days old replacing
dead moths, were added every 3-4 days for life of test moths.

When 75:25 66 :22 were caged, comparable results were obtained.

c The authors were checking temperature effects concurrently.

64

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65

no

CM

£0

ID
S LAID

1 354 (24)

_co

"CN

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DAY EGGS LA
DAY NO EGG

2

29) 1
7)2

8(3) 1
294 (34) 1

"o

00

CN

0 □ "SS

-o o

CN CN

CO ■«*

"*

I

(

CN

Z — n^T

IT) CO

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66
Figure 12 indicates the total number of spermatophores passed by 25 males per day.

Mated males dying prior to replacement of cotton wads with cellucotton wads
passed an average of 3 spermatophores fewer than males after replacement, but the
difference was not statistically significant.

No more than 1 spermatophore was passed per day per male except for male no.
16 which passed 1 spermatophore to each of 2 females the 1st day of caging.

Authors included in Table 6 used various methods to determine spermatophore
passage end acceptance during moth life span. Shorey (1964), Cine (1967),
Hughes (1967), and Stone replaced virgins of the opposite sex daily for life of test
moths. Shorey et al. (1962), Dustan (1964), and Henneberry and Kishaba (1967)
caged moths at various ratios for life of females with no daily replacement of virgin
males. Ouye et al. (1965) initiated studies with 3 virgin females per male and
6 virgin males per female to determine potential mating frequency of males and fe-
males caged for life. Three more virgins were added every 3-4 days during the
test moths1 lives, and dead moths were replaced by virgins to assure receptive moths
of the opposite sex were present.

The average reproductive life of E. lignosellus males, counting from day 1 to
the day the last spermatophore was passed (male no. 20 was not included since it
passed no spermatophore) was 10.2 days (range 3-18, median 11) (Fig. 10). Within
3 days, a!! males except male no. 20 had mated at least once. In 5 days 49% of
all spermatophores were passed, in 14 days 99% (Fig. 12).

The lesser cornstaik borer showed no significant correlation between male mating
frequency (spermatophores passed) and longevity. In contrast, Shorey (1964) reported
the principal factor limiting copulation frequency of T. ni males was longevity.

67

Fig. 12. -Total number of spermatophores passed per day by 25
lesser cornstalk borer males, number of males after
day 13 as indicated

a 24 live males in sample

b 23

c 22

d 21

e 20

68

Shorey (1964) speculated the female may be the limiting partner, determining
the average mating frequency in a population having an equai sex ratio. The
lesser cornstalk borer female is the limiting partner, since males passed an average
of 7.2 4- 0.8 spermatophores during a lifetime when caged daily with 3 virgin fe-
males, while females accepted only 1.7 4- 0.2 spermatophore under comparable
conditions.

Male no. 17 and female no. 8 remained continuously coupled to mates for 3
nights and 2 days before dying. In contrast, male no. 25 coupled on day 5 and
remained coupled with 1 female until day 6, when it uncoupled and mated with
another female. On day 7, it coupled again with 1 female thru day 8 when it un-
coupled. The observations indicated an E. lignosellus male can disengage after
prolonged coupling. Shorey (1964) and Callahan and Chapin (1960) reported that
T. ni and H. zea remaining coupled during the day were unable to disengage and
died coupled. Hughes (1967) mentioned mating pairs of P. operculella unable to
sepcrate. Luginbill and Ainslie (1917) reported a caged pair of lesser cornstalk
borer moths found in copulo unable to uncouple.

Dissections of prolonged coupled moths, in this experiment and in mating-
oviposition cages used in colony maintanence, showed the cornutus, the chitinous
tooth on the everted endophalus, was inserted into the bursa copulatrix and bent
at a right angle to the endophalus where it entered the bursa, thus preventing re-
traction of the endophalus thru the ductus copulatrix. In some cases, a malformed
spermatophore collum and corpus entangled the endophalus and cornutus within the
bursa and ductus copulatrix.

Table 7 compares fecundity results with those of other workers. Fig. 13

69

Table 7. -Fecundity of the lesser cornstalk borer

References
and states

Sample
size ($9)

Mean 4- SE

Eggs laid/female

Range

Stone. Fla.
Luginbill & Ainslie.

1917. Fla. &S.C.
KingetaL 1961.

Texas.
Dupree. 1965.

Ga.
Leuck. 1966.

Ga.
Calvo. 1966.

Fla.

25

35

419.5+ 14.7
192

124

67

293-562
91-342

/(1957)

123.9

11-261

7a(1958)

61

5-221

?

125.7+20.5

2-314

Dupree used 17 55 in 195/- 1958 combined.

70
illustrates the average number and standard error of eggs laid per day. No signifi-
cant correlations were found among longevity, spermatophores accepted, total eggs
laid, sterile eggs laid, and length of oviposition period. Correlation between
number of eggs laid and the number of fertile eggs v/as significant at the 1% level
(r=.8089).

Callahan (1958a) and Shorey (1963) found no correlation between longevity
and total eggs laid for H. zea and T. ni. Shorey (1963) also found egg production
increased as numbers of spermatophores increased for females laying viable eggs,
but percent viability was not markedly correlated with mating frequency.

In the discussion below, day refers to time of pairing, but oviposition day
refers to a day counting from the 1st day eggs were laid by a particular female or
by females. Once eggs are laid, even days without additional egg laying are
counted as "oviposition days" within the oviposition period. This happened only
4 times (Fig. 11).

Of the eggs laid by 25 females, 56% were laid by the 4th oviposition day,
or 48% by the 4th day.

The average oviposition period for 25 females, counting from the 1st through
the last oviposition day was 11.8 oviposition days (range 7-19, median 10) or
14.6 days (range 8-23, median 12) counting from the 1st day of caging through
the last oviposition day. Females delaying oviposition no more than 1 day aver-
aged 11.5 oviposition days (range 7-19), while 5 females delaying oviposition more
than 1 day averaged 13.0 oviposition days (range 10-17). Dupree (1965) found
that the oviposition period was 7U8 days (range 1-18) 1 year and 4.1 days
(range 1-9) the following year. Luginbill and Ainslie (1917) recorded 5 females

71

10 12 14 16

Oviposition Days

Fig. 13. -Average numbers of eggs laid per day by 25 lesser cornstalk borer
females, number of females affer day 12 as indicated. Standard
errors shown with horizontal lines

a

22

b

18

c

17

d

13

e

12

f

9

femal

males in sample

72

oviposited an average of 10.4 oviposition days (range 7-14).

Leuck (1966) staled that caged females oviposited nightly all their lives, but
females in the work reported here lived an average of 4.7 days (range 1-13, median
4) after the last oviposition day. Dupree (1965) stated oviposition usually occurred
on alternating days, rarely on consecutive days. Only female no. 2 laid larger
egg numbers every other day thru day 9, with differences of 50-70 eggs on suc-
cessive days. Perhaps Dupree's moths reflected temperature effects in ihe outdoor
insectary, as he mentioned the average minimum and maximum temperatures during
experimentation were 66.6 and 86.4 F in 1957 and 66.8 and 88.2 F in 1958.
Luginbill and Ainslie (1917) stated oviposition did not occur when the temperature
"fell much blow 80 F," but did not state clearly under what condition moths were
kept. Sanchez (1960) stated field collected adults maintained at 65° F continued
ovipositing, but adults kept at 35 F were inactive. Hov/ever, he did not study
oviposition patterns. Perhaps these discrepancies in responses to temperature re-
flect differing genetic strains.

The variation in numbers of eggs laid on oviposition day 1 (range 2-135,
median 86) might result from varying times of mating and/or varying rates of sperm
passage from the bursa copulatrix to the recepfaculum seminis.

Table 3 summarizes variations from basic oviposition patterns, and includes
only females showing at least 2 of the variations listed. All females laying more
than the average percent sterile eggs of total eggs laid are included (population
average 5.5%, range 0-30.4%). Four of 5 females delaying oviposition more than
1 day, 5 of 8 females retaining more than 10 eggs (population average 8.7, range
1-26), and 3 of 7 females ovipositing in daily numbers differing from the usual

73

Table 8. -Lesser cornstalk borer females showing 2 or more variations from basic
population oviposition patterns.

Female Ave. % Delayed ovipo- Retained 10 Irregular daily

no. sterile eggs sition (days) eggs at death oviposition pattern

+
15

11

26 +

19 +

21

14

30%

-

22

29%

-

21

16%

5

19

13%

-

4

12%

5

11

8%

3

13

7%

7

Laid 2 fertile eggs on day 1.

74
daily decreasing pattern (Fig. 13) are included. Only females no. 21 and 22 laid
more than the average total number of eggs. Females no. 4 and 19 represent the
2 lowest fecundity records obtained.

The data indicate females laying more than the average percent sterile eggs
of all eggs laid tend to show other variations. Seven females not included in Table
8 showed only 1 variation of the 4 Usted.

Nineteen females began ovipositing on day 2. Female no. 22 laid eggs the
1st day of caging, while 5 females delayed oviposition more than 1 day (Fig. 1 1).
A. kuehniella females underwent periods of quiescence after mating, usually 12 to
24 hr. During this time the sperm passed from the bursa copulatrix to the recepta-
culum seminis. Then oviposition began, lasting to within the last day or 2 of life
(Norris, 1933). If this is the case in E. lignosellus, then one could assume the
19 females probably mated on day 1 and were ready to oviposit on day 2. Female
no. 22 must have mated on day 1, as the 2 eggs laid were fertile. The 5 females
delaying oviposition may have mated the day before they initiated oviposition or
perhaps they indicated a wide range of sperm passage rate from the bursa to the
glandula receptaculum.

Thirteen females laid decreasing numbers of eggs from oviposition day 1, dis-
regarding increases of less than 10 eggs in production on 2 successive days. If
oviposition day 1 is disregarded due to the variation in egg numbers laid, then 18
females laid decreasing numbers of eggs daily. Norris (1933) found A. kuehniella
females laid the greatest number of eggs during the 1st 2 days and then decreased
production gradually until the last day or 2 of life, when 1, 2, or no eggs were
laid. This agrees with lesser cornstalk borer egg production, except that E.

75
lignosellus females live longer on the average after the last oviposition day.

Of females differing from the daily decreasing oviposition pattern, 1 tended
to oviposit on alternate days (female no, 2 discussed above), 1 reached peak
production on oviposition day 3, and another on oviposition day 4. Four females
reached a 2nd peak production (at least 15 more eggs laid' than on the previous
oviposition day) after the 1st 2 oviposition days — 2 on oviposition cay 4, 1 on
5, and 1 on 6.

A. kuehniella females laid sterile eggs at any point in life (Norris, 1933).
All gradations in fertilization reduction occurred and oviposition of no viable eggs
was associated with the absence of sperm from the receptaculum seminis of mated
females or with the presence of small quantities of sperm, much smaller than in
normally mated females- When spermatozoa were present, they were less violent-
ly motile than usual, and in some cases they were motionless, perhaps due to re-
tarded spermatogenesis, which also might cause the male to pass reduced quantities
of sperm. Altho the above factors were not checked in my research, they might
have influenced sterile egg production.

Twenty-two females laid less than 10% sterile eggs of all eggs laid on ovi-
position day 1. The 3 females laying more than 10% laid 20, 49, and 66%. Two
females laid sterile eggs every oviposition day (females no. 21 and 22), while 2
females Icid no sterile eggs during the entire oviposition period (females no. 6
and 23).

Concerning spermatophores accepted by females listed in Table 8, 4 females
delaying oviposition accepted 1 spermatophore each. A 5th moth delaying ovi-
position accepted 2 and oviposited in a daily pattern of decreasing numbers of

76
eggs as shewn in Fig. 13. Assuming no pcrthenogenesb occurred, all 5 females
mated on or by oviposition day 1, since each laid some fertile eggs on oviposition
day 1. The other 3 females in Table 8 accepted 1, 2, and 3 spermatophores (fe-
males no. 19, 14, and 22, respectively). Females no. 4, 11, 19, and 21 tended
to lay increasing percentages of sterile eggs daily as fewer eggs were laid. Per-
haps the sperm supply was becoming exhausted with time.

The 3 of 25 females accepting 3 spermatophores retained 14-19 eggs at death.
Five other females (Table 8) (4 accepted 1 spermatophore, 1 accepted 2) retained
more than 10 eggs at death. Correlation between the number of spermatophores
accepted and the number of eggs retained at death was significant at the 5% but
not at the 1% level (r=.5006).

Of females ovipositing daily eggs numbers varying from the basic curve
(Fig. 13), 3 females accepted 1 spermatophore and 4 females accepted 2.

No record was kept of how many eggs were laid by virgin females retained
for life, nor were the eggs retained for hatch. However, other workers hove not
reported that parthenogenesis occurs among the Phycitidae.

Time of Oviposition
Few workers have reported the time of oviposition of the lesser cornstalk
borer. Luginbill and Ainslie (1917) stated that oviposition of caged females be-
gan shortly after dusk and continued until the early morning hours. The majority
of eggs were laid during the forepart of the night. No eggs were laid diurnally
or in bright light at night. Leuck (1966) reported that caged femalss oviposited
shortly after dark and throughout the night.

77

Materials and Methods

Paper sheers were placed on screen tops of 3 mating-oviposition cages as de-
scribed under rearing techniques. The sheets were replaced every 4 hr starting at
3 PM 1 day and ending at 7 PM the following day. To determine if oviposifion
occurred during the hour before the lights fumed off (at 8 PM), sheets v/ere left
on the cages from 7-8 PM at the end of the experiment. All sheets were set aside
for at least 30 hr. The eggs were then counted with the aid of a microscope.

Results and Discussion

All 3 populations oviposited over 90% of all eggs laid from 7-1 1 PM (92,
95, 98%). From 11 PM to 3 AM, the 3 populations oviposited 8, 3, and 2% of
all eggs laid, respectively. The remaining eggs were laid between 3 AM and 7
AM, except for 1 sterile egg laid between 7-8 PM on the 2nd day. Thus moths
oviposit primarily during the 1st 3 hr of total darkness.

Response of Adults to Sound

Sound reception by moths has attracted considerable attention in recent
years. The tympanic organs of noctuid moths are sensitive to sounds ranging
from 3-240 kc/sec with maximum sensitivity between 15-60 kc/sec (Roeder and
Treat, 1957). Tympanic nerve preparations defect bat cries at a distance of 30 m
or more (Roeder and Treat, 1960).

Insectivorous bats use ultrasonic cries to echolocate night flying insects
(Griffin, 1953; Griffin and Novick, 1955; Novick, 1965). Roeder and Treat
(1960) found that many free flying moths perform evasive behavior in the pre-
sence of bats. The same is true when moths are subjected to an artificial

78
approximation of bat cries (Roeder, 1962; Agee, 1967). The intensity of the sound
stimulus is directly related to the type of moth response (Roeder, 1964); diving re-
sponses are most prevalent around 75-85 db, while turning-away responses are
most prevalant around 45-55 db. No evidence indicates tympanate moths can dis-
tinguish differences in sound frequency (Roeder, 1966). It was concluded that the
evasive behavior had a selective advantage and that probably the major function
of moth tympanic organs was to warn night flying moths of approaching bats
(Roeder and Treat, 1960).

Several workers examined practical application of moth response to sound.
Belton and Kemps ter (1962) broadcast ultrasonic sound at 50 kHz and obtained
more than 50% reduction of sweet corn infestation by the European corn borer,
Ostrinia nubilalis (Hubner). Treat (1962) captured more than twice as many tym-
panate moths in silent light traps than in light traps broadcasting recorded ultra-
sonic bat cries. Agee (1967) attempted to reduce oviposition of bollworm moths,
H. zea, and tobacco budworm moths, Heliothis virescens (F.), in cotton fields
with ultrasonic sound. He felt the negative results obtcined were due to equip-
ment failure during the moths' most active periods. Payne and Shorey (1968)
found that pulsed ultrasonic sounds, especially at high intensities, reduced ovi-
position by the cabbage looper moth, T. ni, on lettuce and broccoli crops.

The tympanic organs might have other auditory or proprioceptive functions
unconcerned with bat detection (Trect, 1955), such as echo-location (Roeder and
Treat, 1957). However, Treat (1955) suggested diurnal Lepidoptera possessing
tympanic organs might have recently acquired the diurnal habit, and the organs
have persisted without survival value. On the other hand, perhaps the diurna!

79
fliers also fly at night when an auditory sense might be of more benefit. He men-
tioned the typically diurnal butterflies have a poorly developed auditory sense,
if it exists at all.

Roeder and Treat (1960) inferred that most moths with known auditory organs
are medium sized (10-40 mm wing span). Few of these moths escaped attack by bats
but many escaped capture.

In addition to the tympanic organs, Lepidoptera have several other organs or
structures which may assist in sound perception (Haskell, 1961). These include:
(A) Johnston's organ in the 2nd antennal segment; (3) the subgenual organs,
generally found in the proximal region of the tibiae of all legs; (C) chordoronal
sensillia, scattered about the body; and (D) hair sensillae, scattered over the body
but especially on the thorax and abdomen. All of these structures respond to 10
kc/sec or less so far as is known among the Insecta, but little research has been
done with the Lepidoptera. Functions attributed to the tympanic organs might in
fact be carried out by the above structures in combination with each other and/or
with the tympanic organs, since no one has reported bat avoidance by deafened
moths.

Further, adult Lepidoptera themselves produce sound by various means, but
little is known about their behavioral significance (Haskell, 1961; Alexander,
1967). Haskell (1961) catagorized the principal types of sound producing mech-
anisms into 2 groups. The 1st group includes sounds produced by products of some
usual moth activity, as the ultrasonic sound of 15 kc/sec and possibly higher pro-
duced in the flight of Prodenia eridania. Roeder and Treat (1957) suggested the
sound might be associated with precopulatory behcvior. Shorey (1964) found that

80
bilateral tympanectomy of both sexes of T. ni possibly reduced but did not prevent
successful copulation.

The 2nd major group includes several mechanisms such as factional mecha-
nisms, vibrating membranes, and mechanisms directly involving air movement
(Haskell, 1961). These mechanisms include: (A) scraping raised fore and hind
wing veins together producing frequencies up to 14 kc/sec, as in the Peacock
Butterfly (Nymphaiis jo); (B) rubbing wing ridges with some part of the leg, as in
many noctuid moths; (C) clicking of wing membranes which pop in and cut when
the wings are knocked together, as in Hecatesia; (D) rubbing a ribbed and a
pegged wall of an abdominal cavity together, as in certain Lymantriid male moths;
(E) forcing air thru the proboscis by means of pharynx pumping with the epipharynx
interrupting air flow, as in Acherontia atropos; and (F) possibly forcing air thru
spiracles, as in Arcfia caja.

Perhaps some of the above mechanisms include clues to communication be-
tween the sexes involving sound perception by the tympanic organs, but as Alex-
ander (1967) indicates, this possibility has scarcely been investigated. In addition,
the tympanic organs sense natural sounds other than bat cries, as rustling leaves
and cricket chirps. Other functions could be served by the tympanic organs opart
from bat detection, but no evidence of the importance of such perception is avail-
able as yet (Roeder and Treat, 1961a, 1961b).

The purpose of this experiment was to determine if E. lignosellus adults re-
spond to sonic and ultrasonic sound.

Materials and Methods

A cylindrical cage of fiber glass screen and clear plastic, 6.5 cm high x 2.5

81
cm diam, was used to cage individual test moths. The cage top and bottom peri-
meters were plastic rings 1.5 cm and 0.5 cm wide, respectively. The screen was
sewn together along the side with thread and glued to the 2 rings. A small piece
of fitted fiber glass screen formed the bottom. The cage with a moth was inverted
into a small plastic dish with a fitted cellucotton disk saturated with 2% sucrose
solution.

Preliminary tests indicated 66-100% of moths tested nocturnally (10:30 PM to
1:30 AM) at 3-16 kHz with 3.3-20 volts of amplitude remained quiet throughout
the tests. Other moths moved about the cage and/or stroked their antennae, while
still others extended their abdomens with tone bursts and contracted the abdomens
to the normal position during silence after a tone burst. This latter activity was
used as the criteria for a positive response in the following tests since it was re-
peatable at 20-60 kHz.

Five each 2-day-old males and females were tested for behavioral response
from 2-4 PM and another set of 5 males and 5 females of the same age from 9:45-
1 1:00 PM. The cage was set 46 cm directly in front of a Dukane lonovac^ Duk-5
speaker with a power supply modified for extended frequency response. Pure tones
from 20-60 kHz in 10 kHz increments were produced with a Hewlett-Packard
audio oscillator model 200 CD. Three 1/2 sec tone bursts were separated by 4

CR)

sec using a General Radi<j tone burst generator type 1396-A timed by a Hewlett-
Packard^ audio oscillator model 201 C. At least 10 sec separated a tone burst
triplet from the next.

Voltages of amplitude scale settings were determined with an oscilloscope as:
20 scale setting =1.1 volts; 30 = 1.9 volts; 40 = 3.3 volts; 50 = 6.4 volts; 60 =

82

13.5 volte. A General Radio sound level meter type 1551-B was used to measure
intensity on the A scale at 46 cm from the speaker. At 10 kHz, the following
amplitude scale settings were recorded in decibells: 10 = 54 db; 20 = 61 db; 30 =

66 db; 40 = 71 db; 50 = 76 db; 60 = 80 db. These sound levels correspond to the

CD

above voltages. The loncvac tweeter was found to be linecr within + 2,5 db

between 10 and 60 kHz. Consequently the voltage readings should be convertible
to sound levels with the same scale for all frequencies.

Moths were subjected to various frequencies and amplitudes. In the 1st test,
frequencies were held constant in the following order: 40, 30, 50, and 40 kHz.
In each frequency test, amplitude dial settings were varied in the following order:
60, 40, 20, 30, and 50.

In the 2nd test, amplitude was held constant at full setting (20 volts) as fre-
quency was varied in the following order: 20, 30, 40, 50, 60, 40, 20, 30, 50,
and 60 kHz.

The cage was lighted with about 23 ft-candles during the afternoon tests.
During the evening teste, a 7 1/2 watt red light 7.5 cm distant illuminated the
cage with about 2-3 ft-candles. The room temperature was 27 4- 1 C.

Results and Discussion

In general, moths responded to high and low frequencies at high amplitudes
(Fig. 14). Females responded essentially the same during day and night, but
males were more responsive at night.

The test of bilateral tympanectomy on sound response was attempted but
abandoned due to moth size and delicacy and the tympanic organ position. The
wings, thorax and/or abdomen were usually damaged during the operation. Unlike

83
nocfuid tympanic organs, those of E. lignosellus are located on the 1st abdominal
segment and are covered by the metathoracic coxae. In addition, a fan of elon-
gated scales originating on the abdominal pedicel obscures the tympanal surface.
The operation was performed by anesthetizing a moth with CCU, placing it on its
back, pressing with a pin on the sclerotized rim surrounding the tympanic organs,
and thrusting the pin point dorsally and posteriorly simultaneously. The operation
was essentially done in the blind. Often the tympanic membrane and scolopo-
phorous organ were still intact in moths checked later to determine operational
success.

E. lignosellus is responsive to sound, but whether this is due to reception by
the tympcnic organs was not determined. The function of the tympanic organs in
E. ligncseilus is unknown.

84

? 5r

Z I 3

11

-o-o

0 4 8 12 16

Amplitude (volts)

30 kHz

12 16

Amplitude (volts)
40 kHz

0 4 8 12 16
Amplitude (volts)
50 kHz

Diurnal response

Amplitude (volts)
30 kHz

Amplitude (volts)
40 kHz

Amplitude (volts)
50 kHz

Nocturnal response

iOr

o c

. o

£ 9r

I 2

Z t£

o

E

0 20 40 60

kHz
Amplitude 20 volts

Diurnal and nocturnal
response combined

— o $ response
-o C* response

Fig. 14. -Diurnal and nocturnal response of lesser cornstalk borer adults to various
amplitudes and frequencies.

SUMMARY

Need for basic research on the reproductive biology of the lesser cornstalk borer,
Elasmopalpus lignosellus (Zeller) (Lepidoptera: Phycitidce) prompted this research.
The borer reportedly attacks 62 host plants representing 14 plant families, but host
records may be incorrect due to similar feeding habits of other species.

A rearing technique was developed. Sixty to 80 pupae were obtained per 100
eggs. Tote I time from egg to adult was 24-28 days. The colony was reared for 34
months or approximately 32 generations. Ninety-five percent of pupae obtained
were normally formed. Lightly sclerotized aberrations occurred on the venter of 5%
of pupae obtained. Approximately 92% and 78% emergence of normal adults was
obtained from normal and aberrant pupae respectively.

The male and female reproductive systems, including spermatophore morphology
and position in the bursa, were studied and compared with other Lepidoptera. Color-
less fluid in the 1st secretory area of the primary simplex of the male indicated a
mating (=spermatophore transfer) less than 24 hr previously. Virgin 1-6-day-old
males had translucent yellow simplex fluid, and males that mated 2-5 days pre-
viously had transparent yellow simplex fluid. Within 24 hr after mating, simplex
fluid in 3-day-old mated males changed from transparent colorless to transparent
yellow. Color of spermatophores representing 3 successive matings was clear trans-
parent. Thus 1st matings were indistinguishable from subsequent matings on the

85

86
basis of spermatophore color. Females had no full-sized eggs af emergence, but
might have them present in the calyx, lateral oviducts, ana/or common oviduct as
well as in the ovarioles within 1-2 days after emergence.

The abdominal tympanic organs were studied and compared with the general
pyraloid description. The tympani were ventrally and anteriorly located on the 1st
abdominal segment.

Mating occurred in 40-dr vials but not in 4-dr vials. In the 40-dr vials no
significant differences in mating success occurred in respect to cage position, cage
top materials, and fed versus unfed moths for a single mating per pair. Fed moths
were more likely to mate again than unfed moths.

Mating behavior was observed, including pair formation, courtship, time of
coupling, duration of copulation, uncoupling of mates, and post copulatory activity.
Pair formation and courtship behavior included activities suggestive of olfactory
stimuli. Mating occurred from 1:40 AM to 6:40 AM. Males mated with approxi-
mately equal frequency when caged for 1 day with 1, 2, 3, or 4 females. One- to
6-doy-old moths mated equally well. Complete bilateral antennectomy of males
inhibited mating.

Virgin males lived 42.4 4- 1.7 days (mean 4- standard error), mated males 24.2
4- 1 .5 days, virgin females 37.6 4- 1.8 days, and mated females 18. 1 4- 1.7 days.
Males passed 7.2 4- 0.8 sperrnatophores each and females accepted 1.7 4- 0.2 sperma-
tophores each in a lifetime. There was no significant correlation between longev-
ity and sperrnatophores passed. Females laid 419.5 4- 14.7 eggs each of which
5.5% were sterile and retained 8 eggs at death. Oviposition began the 2nd day of
caging with males, and decreasing numbers of eggs were laid daily throughout the

87
oviposiMon period. Females oviposited 48% of all eggs laid by the 4th day of
caging with males. Females laying more than the average percent of sterile eggs ■
tended to delay oviposition more than 1 day, to retain more than 10 eggs at death,
and/or oviposit non-decreasing daily numbers of eggs during the oviposition period.
There was no significant correlation among longevity, spermatophores accepted,
total eggs laid, sterile eggs laid, and length of oviposition period. Correlation
between number of eggs laid and number of fertile eggs was significant at the 1%
level (r=8089). Correlation between the number of spermatophores accepted and
the number of eggs retained at death was significant at the 5% level (r=5006).
Moths responded to sound of high and low frequencies at high amplitudes.
Males were more responsive nocturnally than diumally, but females showed little
differentia! response.

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BIOGRAPHICAL SKETCH

Kari Johnson Stone was born in Petoskey, Michigan, on 7 February 1935. He
received his primary education at Central Grade School and his secondary edu-
cation at Petoskey High School, graduating in June 1953. He entered the Uni-
versity of Michigan in the fall of 1953, and received the degree of Bachelor of
Science in June 1957.

He was admitted to the Graduate School of the University of Michigan in
September 1957, and received the degree of Masters of Science in Biology in June
1959.

He was appointed to the position of Scientific Technician with the Arctic Re-
search Laboratory, operated by the University of Alaska under contract with the
Office of Naval Research in September 1959, and held the position until he was
cppcinred Administrative Assistant to the Director, Arctic Research Laboratory, in
August 1961.

He was admitted to the Graduate School of the University of Florida in
September 1962. He was appointed to the position of Laboratory Technician with
the Florida Department of Agriculture, Division of Plant Industry in July 1963 and
held the position until June 1965. He was appointed to the position of Research
Associate with the University cf Florida, Department of Entomology, in July 1965.

95

96
Karl J. Stone is married to the former Margaret Ann Brand, and is the father
of one child. He a member of the American Museum of New York, Society of
Systematic Zoology, Entomological Society of America, and the Florida Entomo-
logical Society.

This dissertation was prepared under the direction of the chairman of the
candidate's supervisory committee and has been approved by all members of that
committee. It was submitted to the Dean of the College of Agriculture and to
the Graduate Council, and was approved as partial fulfillment of the require-
ments for the degree of Doctor of Philosophy.

December, 1968

^V

/ft

/ Dean, College of Agriculture

Dean, Graduate School

Supervisory Committee:

Chairman

^C'VvnfUn C ch^b-^*

n^°-