Studies on some aspects of the biology of Corcyra cephalonica (Stainton) (Lepidoptera: Galleriidae)

J. t/m~d Prorl. Rr.r. Vol. 3. No. 4, pp. 181-186. Printed in Great Bnraln. All rights reserved

1989 Copyright

0022-474X:X9 $3.00 + 0.00 f(- 1989 Pergamon Press plc

STUDIES ON SOME ASPECTS OF THE BIOLOGY CORCYRA CEPHALONICA (STAINTON) (LEPIDOPTERA: GALLERIIDAE)

OF

GEORGEN. MBATA School

of Biological

Sciences,

Imo State University,

PMB 2000, Okigwe.

Nigeria

(Received 21 April 1989) Abstract--The biology of Core~ra cephalonica (Stainton) was studied under controlled conditions in the laboratory. At a constant temperature of 30°C. oviposition was influenced by relative humidity, an average of 148.9 eggs per female being laid at 70% r.h., compared with 131.8 eggs at 50% r.h. More eggs were retained in the ovaries of dead females at the lower r.h. Maize, rice and groundnuts were preferred to cowpea and cocoa for egg deposition. The incubation period was about 4 days at both humidities. Larval development was fastest at 70% r.h. (34.1 days) and slowest at 50% r.h. (43.3 days). Pupal duration was not affected by relative humidity. Development on different forms of a range of food commodities was studied. The larval period was generally shortest on brokens and meal, particularly of maize. Adult moths appeared weakly negatively phototactic and most locomotory activities were observed to take place at dusk.

INTRODUCTION Corc:~~/ c,ephu/onica (Stainton), commonly known as the rice moth, is a cosmopolitan pest attacking a number of stored products. The commodities attacked include rice, sorghum, maize. milled cereals, cowpea, cocoa, groundnuts, almonds, dates, cashew nuts, raisins and millet (Adeyemi, 1968; Hodges, 1979). Studies on the developmental biology of the moth have shown that its previous ecological history can have an effect on its developmental biology, For example, Cox et al. (198 1) found considerable differences in the proportions of eggs hatching in strains of the moth from Malawi, Nigeria and Burma, with a high percentage of infertility in the eggs of a Nigerian stock. Strains from different countries also seem to have differing food preferences for development. A strain from Tchad studied at 28”C, 70% r.h., exhibited 36 and 58% survival from egg-hatch to adult on millet and sorghum, respectively, while the survival rates of a Cameroon strain were 69.7 and 48% on millet and sorghum (Russel et al., 1980). Osman (1984) observed survival rates of 63.5 and 55.1% in a strain from the U.S.A. on millet and sorghum. Cox et ul. ( 198 1) found very low cold tolerance of eggs of C. cephalonica from the tropics, and better adaptation of strains from the Sahel to development under dry conditions than strains from humid West Africa. The present work was aimed at studying aspects of the biology of C. cephalonica from the humid south of Nigeria.

MATERIALS

AND

METHODS

Sours*e ulzd culturing qf experimental insects The moths used were obtained from grain stores at Umuahia main market in Imo State, Nigeria. The moths were reared in transparent glass jars measuring 23.5 x 9.0 cm and fed on dietary mixture referred to as “moth medium”, comprising poultry laying mash (15 parts), chick starter mash (15 parts), grower’s mash (15 parts), rolled oats (10 parts), glycerine (4 parts) and brewer’s yeast ( 1 part). The above ingredients, with the exception of glycerine and yeast, were first kept in a freezer for 7 days to kill any mites or parasites present. The medium was then thoroughly mixed and kept for 3 days to equilibrate with laboratory conditions. Adults used in the experiment were collected as soon as they emerged from the culture medium and stored singly in 75 x 25 mm tubes. Moths used in this study were O-24 hr old except where otherwise stated.

182

GEORGEN. MBATA

Eflect of relative humidity on oviposition at 30°C Female moths were paired with male moths in 1: 1 ratio in 75 x 25 mm tubes. The tubes were thereafter covered with filter paper glued on to the tubes with petroleum jelly. Oviposition was observed at 3O”C, 50% and 70% r.h. The relative humidities were maintained with sodium hydroxide solutions as described by Madge (1961) and monitored using cobalt thiocyanat~ paper and comparator (Solomon, 1957). Twenty tubes containing pdired moths were put in each of two desiccators containing the relative humidity solutions. The desiccators were then placed in an incubator maintained at 30°C. The tubes and the filter papers which covered them were checked for eggs at 07.00 and 19.00 hr each day until the female moth died. The ovaries of the dead females were dissected out within 12 hr of death under a binocular microscope to record the number of ripe eggs retained in the ovaries. Commodity preference for oviposition Whole kernels of maize, rice, groundnuts, cowpea and cocoa were investigated for preference as sites for egg deposition by C. cephalonica. Sufficient kernels of each commodity were put in separate 8 cm diameter petri dishes to cover the bottom of the dish. An empty petri dish served as the control. The 6 petri dishes were arranged tangentially inside a trough and distances between successive petri dishes were equal. The trough was then covered with muslin taped to its side but leaving a little space for the introduction of 10 pairs of newly-emerged moths. The trough was closed after introduction of the moths and placed in a dark chamber at 27 rf: 2.5”C and 70 + 10% r.h. After 3 days the eggs deposited on the different commodities were brushed off and counted. Seven oviposition trials were carried out during which the positions of the petri dishes were changed. Incubation period of eggs at two relative humidities at 30°C Newly laid eggs (O-12 hr old) were distributed 10 each in 30 specimen tubes of dimensions 50 x 25 mm. These tubes were equally distributed between two desiccators maintained at 50 and 70% r.h. respectively, and placed in a GaIIenkamp cooled incubator maintained at 30 it O.SC. Temperature was monitored using a thermometer dipped in glycerine. The incubation period of the eggs and the number of hatched eggs at each r.h. were noted. Eflect of relative humidity on development at 3O’C Approximately 3 g of broken groundnuts were weighed out into each of 45 tubes of 2.5 cm dia. The tubes were distributed between 3 desiccators maintained at 50, 60 and 70% r.h. using relative humidity solutions as already described and the desiccators put in an incubator set at 30°C for one week in order to condition the food. Four newly hatched larvae (O-24 hr old) were introduced into each tube using a camel-hair brush and the tubes covered with muslin secured by a rubber band, The tubes were examined on alternate days until pupation after which daily observations were made in order to record the dates of adult emergence. Development on diflerent food commodities Three media of groundnuts, rice, maize, cowpea or cocoa, namely whole and broken seeds, and the meal were investigated. Broken seeds were produced by spinning in a blender for 10 set while the meal was produced by spinning for 1 min and removing coarser particles in a 20-mesh sieve. All the diets were frozen for 14 days before use in order to eliminate any infestation that might be present. About 4 g of each diet was weighed out into glass tubes (75 x 25 mm), in replicates of eight, which were then placed in desiccators maintained at 30 + 0.5”C. 70% r.h. for 2 weeks to equilibrate. Four newly-hatched larvae were then placed in each tube, and observations carried out until all larvae had either pupated, emerged as adults or died. Dates of pupation, adult emergence and weight and sex of emerged adults were recorded. ~ocomotory activities of adults Adult moths were put in a 36 x 12 cm transparent glass container covered with muslin to admit light and air. Observations lasting 20 set were made every 30 min between 08.00 and 24.00 hr. The number of starts for walking, running or flight was recorded using tally counters. During the night

of C. cephalonica

Biology Table

I. Effect of relative

humidity

183

on oviposition Relative

at 30 C humidity

(%)

70 Number of eggs laid per female moth (mean i SE)

50

14X.9 + 6.5”

131.8*4.lb

Eggs laid (%) within 2 days of oviposition (mean)

66.5

75.5

Eggs laid (%) within 4 days of oviposition (mean)

X9.8

99.6

Duration (days) of ovIposition (mean + SE)

5. I

Number of eggs dissected out of the ovaries of dead females (mean t SE)

+ 0.3

6.5 +

Horizontal va!ues having different superscripts son was done with Student’s i-test.

4.2 _+ 0.X”

I .3”

19.0 _t 2.9h

are significantly

different.

Compari-

a torch covered with sack-cloth was used to record the locomotory activities. The locomotory activity of virgin adults (10 males and 10 females) was compared with that of mated individuals (10 males and 10 females) and the effect of density on locomotion was investigated by using 5, 10 or 15 pairs of previously mated adults. RESULTS

AND

DISCUSSION

Action of relatioe humidit?, on oviposition

The mean number of eggs laid at 70% r.h. (148.9) was significantly higher than the number laid at 50% r.h. (131.8; P < 0.05. Table 1). It seems possible that this result was influenced by temperature, since Russell et al. (1980), working at 28°C observed that r.h. had no effect upon oviposition. Most of the female moths commenced oviposition within 18 hr of mating. Egg laying took place at night and was almost completed within 4 days (Table 1). These observations are in agreement with those of Carmona (1958). The duration of oviposition was longer at 70% r.h. than at 50% r.h. but not significantly so. The mean number of ripe ova retained in the ovaries after death was found to be significantly higher at 50% r.h. (19.0) than at 70% r.h. (6.5) (P < 0.05). This is in agreement with previous observations on Plodia interpunctella (Hubner) (Mbata, 1985). Choice if’ commodities ,for egg deposition

Under the condition of the choice chamber experiment conducted there were clear indications of a preference for maize, rice and groundnuts as oviposition substrates, possibly the result of olfactory attraction. The mean number of eggs deposited on these substrates ranged between 289.0 and 330.5 (Table 2). The number of eggs deposited on these commodities were not significantly different but were significantly higher than the numbers deposited on cowpea, cocoa and glass (P < 0.05). Cocoa was the least favoured commodity for oviposition. Incubation period of eggs at t\tsorelative humidities

There was no significant effect of relative humidity upon incubation period at 30% (Table 3); although the mean of about 4 days was shorter than that recorded (5.2 days) by Osman et al. (1984) at 3O”C, 68% r.h.. it is in agreement with the observations of Shazali and Smith (1986), Tauthong Table 2. Choice of substrate

for deposition

of eggs

Substrate Marze Mean number of eggs deposited SE

289.0’ * 21.2

Groundnuts

326.8’ i 14.6

Cocoa

Rice

79.6b i1I.4

330.5’ F 20. I

Values having different superscripts are significantly different. Comparison multiple range test (shortest significant ranges. SSR).

Cowpea

123.6b k 13.6

Empty dish (glass)

6.66 0:

was done using Duncan’s

184

GFORGE

N. MBATA

Table 3. Effect of relative humiditv on incubation neriod at 3o‘C Relative humidity (%) 70

50

Number of eggs hatched (out of IO) (mean f SE)

9.4 + 0.2”

9.1 + 0.Y

Incubation period (days) (mean 5 SE)

4.1 * 0.01’

4.2 f 0.04”

Number of eggs hatched within 4 days

8.7 f 0.08”

7.8 5 0.2d

Number of eggs hatched after 4 davs

0.7 + 0.04

1.3 io.2

Horizontal values having the same superscripts are not significantly different. Comparison was done with Student’s r-test.

(1984) and Cox et al. (1981) under similar conditions. The proportion of eggs hatching was high (average 90%) at both levels of r.h. and higher than that recorded by the authors mentioned above. Cox et al. (1981) recorded only 27.5% egg hatch in his Nigerian stock, suggesting the existence of distinct strains of the moth in Nigeria. _Efect of relative humidity on development

Larval development was significantly shorter at 60 and 70% than at 50% r.h. (Table 4). Although the larval period was shortest at 70% r.h. (34.1 days), this did not differ significantly from that at 60% r.h. Relative humidity had no effect upon pupal development. These results are generally in agreement with those of Cox et al. (1981), Russel et al. (1980), Osman et al. (1984) and Shazali and Smith (1986). Survival to adult was greatest at 70% r.h. and these moths were heavier than those reared at the other relative humidities (Table 4). Development of C. cephalonica on various feeding stufSs

Larval development periods were shortest, 29.2 and 26.7 days, respectively, when reared on broken maize and maize meal, and longest, 48.1 and 47.2 days, respectively, on whole and broken cocoa beans (Table 5). The duration of larval development on whole and broken cocoa beans was significantly longer than on any other medium. No development took place on groundnut meal. Pupal development was not greatly affected by food commodity. The mean number of individuals surviving to adult was highest when reared on broken maize, maize meal, whole and broken groundnut kernels, and broken cowpeas. Survival was poorest on cocoa beans and whole cowpeas. Other workers have reported similar observation on the effect of larval food on development. For example, Tauthong (1984) found that rapid development of C. cephalonica larvae occurred on broken but not on whole maize and that broken pulse were suitable for larval development. Development on rice was slower than on maize, cowpea and groundnuts. Whereas Osman (1984) observed that the moth developed faster on sorghum and millet than on rice, Tauthong (1984) recorded similar development periods for all three commodities. It would appear that there are differences between strains in this regard, perhaps influenced by commodities grown and stored in a particular area. The development period was influenced not only by the commodity but by its physical form, development being quicker on brokens and meal than on whole seeds. Although development was faster on meals than on brokens, the latter were more productive in terms of numbers of emerging Table 4. Duration of larval and pupal development at three relative humidities at 30 C

Relative humidity (Oh) SO 60 70

Mean number of individuals surviving to adult (out of 4)

I .9 f 0.44 2.0 i 0.4” 3.2 I 0.5b

Larval period (days) mean i SE

Pupal period (days) mean f SE

Development period egg hatch to adult (days) mean + SE

43.3 f 1.3” 35.8 f 0.9b 34. I + 0.7b

7.6 i 0.2” 7.3 _t 0.3” 7.5 f 0.2”

50.9 * I .4” 43.1 + I.Ob 40.5 + 0.6b

Weight of emerged adults Male

Female

8.7 k 0.6” 11.5~0.5~~ 12.7 + l.Ob

15.8 i 0.8” 19.8 + 0.7”” 22.4; 0.4b

Vertical values having different superscripts are significantly different (P < 0.05). Grouping was done using Duncan’s multiple range test (SSR).

Biology

l;thle 5. Duration of larvaland

Clmlmodity

pupal development

Larva

of C. ee~~u~u~~cff

185

and adult weight on different food types. Duration

Pupa

Egg hatch-adult

of development

No. of adults emerging (out of 4 mean 4 SE)

Male

(days-mean

i SE)

Adult weight mg (mean & SE) .--...-. Female

Groundnu(

Whole Broken Meal

38.0 * 0.9” 34.1 * O.Ib -

7.5 * 0.4” 7.5 t 0.2’ -

45.4 * 1.1’ 40.5 + 0.Q

3.1 + 0.2” 3.3 & 0.3” -.

11.6 + 0.6”b 12.5 * l.lb -

22.7 f I.Zh 25.4 _t I 6’

C’ocw

Whole Broken MCdl

48.1 2 0.7d 47.2 + l.9d 35.4 13 1.9h

8.2 & 0.3db 8.3 + 0.23b 8.6kO.l”

56.3 + 0.4’ 55.4 + 1.4d 44.0 * 1.2c

I. 1 & 0.5” 2.9 & 0.3bc 2.6 f 0.3”

12.4 + 0.4b 13.42 1.3& 14.3 + I.?’

17.2 2 0.v 17.2 rt 0.8” 17.2 It O.hJ

MXCe

Whole Broken Meal

37.7 * 2.Ob 29.2 4 0.6” 26.7 * 0.46

7.5 *0.3a 7.6 kO.ld 7.6 i: 0.26

45.2 k 2.7’ 36.8 + 0.5”h 34.3 + 0.38

2.4 ri O.Sb 3.9 & 0.3’ 3.5 * 0.3’

12.2 & O.gb 13.8 t OSh 16.2 2 l.Od

25 3 i_ 1.0 28.6 it 0.9” 17.8 f I./J

Rice

Whole Broken Meal

41.6 _i: 3.2’ 41.4 r 3.0’ 39.3 rt i .9C

7.7 8.4 8.6

+ 0.2J + O.Z”b ;_ 0.2”b

49.3 k 2.8” 49.8 + I .Fd 41.9 I I .2d

1.5 f 0.3h 2.6i: 0.3h 2.2 * 0.3h

8.7 If: 0.3” 11 .o -i_0.2dh 10.0 * 0.8”

15.7 * 0.4’ 18.2 f o.f?h ‘I.5 _t ?.Ih

CbVpCd

Whole Broken Meal

35.3 i: 1.Ob 30.0 i: 0.3”b 31.8 rt 0.9”h

8.2 * O.Z”b 7.6 + 0.1” 8.5 +O.l”b

43.5 + 0.5’ 31.6 k O.Zah 42.3 k 0.6h

I .9 f 0.4”h 3.3 i 0.3t”‘ 2.8 * 0.2k

10.2 If: 0.5” 16.3 ?r 1.0” 15.8 i_ 2.5’

23.2 i 0.3” 25.0 ir I.? 2x.5 i: ‘.5d

Horizontal values having different superscripts are significantly different (P < 0.05). Gri~uping of the means was done with multiple range test (shortest significant ranges).

adults. These results are in agreement with those of Rao (1954), Carmona (1958). Uberoi (1961) and Tauthong (1984). The high mortality of larval stages of storage moths on groundnut meal is in agreement with the observations of Lecato (1976) and Mbata and Osuji (1983). As previously observed by Waloff and Richards (1946) in Ephestia eluteila (Hubner) and Mbata and Osuji (1983) in P. interpunctella {Hubner), C. cephalonica adults were found to be weakly negatively phototactic, diffused day-light appearing to inhibit locomotory activity. The greatest activity in flight and wandering took place at dusk between 19.00 and 20.00 hr (Fig. 1). Males, particularly when unmated, were more active than females. Unmated males had about the same degree of locomotory activity as mated mixed males and females. Males exhibited some locomotory signals on approaching the females. These signals included dashing runs and fluttering of wings. High densities caused restlessness in the moths and the total locomotory activity increased (Fig. 3). 2%

Time of day Ihours

Fig.

I. Locomotory activity in isolated sexes of C. compared with mixed sexes at 75% r.h. and 27 + I ST.

cephalunica

I =-.aL

0800

12.00 16.00 Time of day (hours)

2000

2L.00

Fig. 2. Effect of density on locomotory activity of adult f. cephalonica at 75% r.h. and 27 + 1.5’C.

186

GEORGE N. MBATA

REFERENCES Adeyemi S. A. 0. (1968) A laboratory study of competition between Tribolium casfaneum (Hbst) (Coleoptera:Tenebrionidae) and three moth species. Bull. ent. Res. 58, 3145. Carmona M. M. (1958) A entomofauna dos produtos armazenados Corcrra cephalonica (Stainton). Estudos, Ensnios Documenfos, Vol. 55. Ministerio do Ultrama. Lisboa. Cox P. D., Crawford L. A., Gjestrud G., Bell C. H. and Bowley C. R. (1981) The influence of temperature and humidity on the life cycle of Corcvra cephalonica (Stainton) (Lepidoptera:Pyralidae). Bull. em. Res. 71, 171-181. Hodges R. J. (1979) A review of the biology and control of the rice moth Corcyra cephalonica Stainton (Lepidoptera: Galleriinae) Rep. Trap. Prod. Insf G 125, 20 pp. Le Cato G. (1976) Yield, development and weight of Cadra caufellu (Walker) and Plodia interpunctella (Hubner) on twenty-one diets derived from natural products. J. stored Prod. Res. 12, 4347. Madge D. S. (1961) The control of relative humidity with aqueous solutions of sodium hydroxide. Entomologia exp. uppl. 4, 143-147. Mbata G. N. (1985) Some physical and biological factors affecting oviposition by Plodia inferpunctella (Hubner) Lepidoptera: Phycitidae) Insecf Sci. Applic. 6, 5977604. Mbata G. N. and Osuji F. N. C. (1983) Some aspects of the biology of Plodia inferpunctellu (Hubner) (Lepidoptera:Pyrahdae), a pest of stored groundnuts in Nigeria. J. stored Prod. Res. 19, 141-I 51. Osman N. (1984) Assessment of damage by the rice moth Corcyra cephalonica (St.) on different grains at four levels of moisture content. Proc. 7th ASEAN Tech. Seminar on Grain Post Harvest Technol., Kuala Lumpur. 1984, pp. 55-61. Osman N. B., Wright V. F. and Mills R. B. (1984) The effect of temperature on certain aspects of the biology of Corcyra cephalonica (St.) Proc. Third Inf. Wkg Con/Y Stored Prod. Em. Manhattan, Kansas, pp. 999106. Rao D. S. (1954) Notes on rice moth, Corcyra cephnlonica (Stainton) (Family Galleridae. Lepidoptera). Indian J. Ent. 16, 95-l 14. Russell V. M., Schulten G. G. M. and Roorda F. A. (1980) Laboratory observations on the development of the rice moth Corcyra cephalonica (Stainton) (Lepidoptera :Galeriinae) on millet and sorghum at 28°C and different relative humidities. Z. anger Enf. 89, 488498. Shazali M. E. H. and Smith R. H. (1986) Life history studies of externally feeding pests of stored sorghum, Corcyra cephalonica and Tribolium castaneum. J. stored Prod. Res. 22, 5561. Solomon M. E. (1957) Estimation of humidity with cobalt thiocyanate papers and permanent colour standards. Bull. ent. Res. 48, 489-506. Tauthong P. (1984) Biological study and effects of some food media and temperature on the survival and development of Corcyra cephalonica (Stainton) Proc. 7th ASEAN Tech. Seminar on Grain Post Hawesf Technol. Kuala Lumpur. 1984, pp. 1433150. Uberoi N. K. (1961) Nutritional requirements of the larvae of the rice moth Corcyru cephalonica-Studies on feeding response to various natural foods. Proc. Indian Acad. Sci. B, 53, 234-247. Waloff N. and Richards 0. W. (1946) Observations on the behaviour of Ephestia elutellu (Hubner) (Lepidoptera: Phycitidae) breeding on bulk grain. Trans R. ent. Sot. Lond. 97, 2999335.