Social influences on nymphal development in the cockroach, Diploptera punctata

Solitary male nymphs of the cockroach Diploptera punctata (Eschscholtz) (Blattaria: Blaberidae) took significantly longer to reach adulthood than males paired with either a male or female nymph or grouped with four other male nymphs since birth. When isolated throughout nymphal development, 15.8% of males passed through 3 stadia before adult eclosion, and the remainder went through 4 stadia. In contrast, 61.3% of paired males became adults in 3 stadia. Males need not, however, be isolated or paired for the entire nymphal period to express isolated or paired patterns of development. About 60% of males paired in just the first stadium or its initial 9 days became adults in 3 stadia, and only 20.4% of males isolated in the first stadium and the first 3 days of the second reached adulthood within 3 stadia. Although the first stadium was a critical period in which social condition determined the course of future development, analyses of covariance showed that isolated males gained less weight than paired ones, not only in the first stadium, but in the second as well. Moreover, the degree of growth of a male in the second stadium, measured as either weight gain or relative growth rate, did not depend on the male's social condition in the first stadium, because isolated second-instar males grew less than paired ones, even when both sets of insects had been paired in the first stadium. Female nymphal development, unlike that of males, was not greatly affected by social factors.     

Changes in the titer of the female-predominant storage protein (81K) during larval and pupal development of the waxmoth,galleria mellonella

The levels of an 81K storage protein in the waxmoth, Galleria mellonella, were monitored during the course of development using rocket immunoelectrophoresis. During the fifth and sixth larval stadia, 81K protein levels increased during feeding and growth but sharply declined at each larval molt. During the fifth and sixth stadia hemolymph levels of the 81K protein increased to about 1 and 2.5 mg/ml, respectively, with no discernible differences between levels in males and females. Neither the fat body nor the remainder of the carcass contained the 81K protein, indicating that the accumulation of this protein during the intermolt period was exclusively in the hemolymph and redistribution of the 81K protein into other tissues does not occur at the final two larval molts. During the seventh (final) larval stadium the absolute quantities of the 81K protein increased from 23 μg per insect to over 1,600 μg in females and to 300 μg in males. The hemolymph concentration of the 81K protein reached 28 mg/ml in females and 6 mg/ml in males with only low levels found in the remaining tissues. Shortly after pupal apolysis, marked by eyespot retraction, the fat body in both sexes rapidly and quantitatively sequestered the 81K protein from the hemolymph. The 81K protein in the hemolymph of both males and females rapidly dropped to nearly zero concentration by pupation. The 81K storage protein remained localized in the fat body cells after uptake occurred, even though the fat body cells disaggregate and reaggregate during metamorphosis. During pharate adult development the 81K storage protein disappeared from the fat body without entering the hemolymph. At adult eclosion 81K was virtually absent from the tissues of both males and females.     

Environmental influences on the gametic investment of yellow dung fly males

The energetic investment per spermatozoon and in spermatogenesis is central to a male's reproductive strategy. Relatively little, however, is known about environmental influences on variation in male allocation decisions and associated trade-offs. Plasticity in sperm length and testis size in response to variable food and temperature conditions either before or after adult eclosion was investigated in Scathophaga stercoraria, a classic model organism for sperm competition. Both measures showed interesting and clear environmental effects and also a heritable component. Testis length, and thus presumably sperm production, showed a hypoallometric (b < 1), but non-linear increase with body size, indicating that the allometric relationship changed with size. Like body size, testis length decreased with increasing developmental temperatures, but also showed a complex cubic relationship with adult temperatures. In contrast, sperm length increased or showed a negative quadratic relationship with increasing temperatures. The increase of within-male variation in sperm length with increasing developmental temperature and decreasing adult food indicates that some of our treatments were stressful. Nevertheless, there was no evidence of a trade-off between testis size and sperm length. The missing effect of adult or larval food availability on testis and sperm length, despite strong effects of larval food on body size, suggests that investment into reproduction is less sensitive to food restriction than investment into growth.     

Male age: effect on mating behaviour and success in the cockroach Diploptera punctata

Older cockroach, Diploptera punctata, males (28 days old) transferred more sperm and larger spermatophores to females than 8-or 14-day-old males. In one male: one female behavioural tests, no significant correlations were found between either how rapidly males initiated courtship with females (response time), or intensity or duration of courtship, and the number of sperm or size of spermatophore subsequently transferred. Eight-day males were slower to initiate courtship than 28-day males. There was no significant differences in the duration of courtship for 8-, 14- and 28-day males, even though the mean duration of courtship was more than twice, as long for 8-day males compared with 14- and 28-day males. In competitive mating tests with one female and three males, one of each age, 28-day males were significantly more successful than 8- and 14-day males. It is concluded that the greater success of 28-day males is due to differences in male behaviour rather than to female discrimination.     

A secondary sex trait under construction: age- and nutrition-related salivary gland development in a scorpionfly (Insecta: Mecoptera)

Males of Panorpa vulgaris Imhoff and Labram, 1836 (Insecta: Mecoptera) can apply three alternative mating tactics to gain access to female mating partners: (1) without nuptial feeding, (2) providing females with a dead arthropod or (3) producing salivary masses. Providing females with salivary masses during copulation leads to the highest reproductive success, as it results in longer mating durations relative to the other tactics. While the number of sperm transferred correlates with the duration of copulation, the sperm of different males are used according to the fair raffle model. Therefore, salivary mass production is an important fitness determining factor for males. In order to provide females with salivary masses, males must first produce and store saliva secretion inside their salivary glands. The present study was concerned with the development of male salivary glands (= production of saliva) in the course of time after adult emergence. We can show that saliva production did not start before adult emergence, that the state of development of salivary glands was affected by larval nutrition as well as by adult nutrition and, moreover, by age. Older individuals had developed glands of greater mass than had younger animals. After receiving a one‐time feeding immediately after eclosion salivary gland mass increased, while body mass decreased with age. Therefore, male P. vulgaris were able to enlarge the amount of their mating resources (= saliva) independently from external nutritional supply (after the initial feeding) and at the expense of losing weight. Possible reasons and functional explanations are discussed.     

Effect of constant light on male sterility in the cotton leafworm Spodoptera littoralis

Females of the cotton leafworm (Spodoptera littoralis) reared in long day conditions (LD 16:8 h) and mated to males kept throughout the whole period of development in continuous light (LL) oviposit very small numbers of mostly sterile eggs. It was found that in control males reared from the first larval instar in long day conditions there was a large accumulation of euperene sperm bundles in their testes on day 1 after imaginal moult. On day 10 of adult life the number of the sperm bundles was very small. In males kept from the first instar in continuous light there was also high number of sperm bundles on day 1 after imaginal moult but it did not decrease significantly on day 10 as was observed in controls. Transfer of different developmental stages of S. littoralis from long day conditions to continuous light resulted in a big difference in the density of eupyrene sperm bundles in their testes. In control insects reared through the whole of their development in long day conditions there was a significant decrease in the density of eupyrene sperm bundles on day 10 of adult life. By contrast, in males in continuous light, regardless of their developmental stage when transferred, there was either no change in density of sperm bundles in day 10 adults or there was a significant increase in comparison with day 1 adults. The highest density of eupyrene sperm bundles was observed in day 10 adults when they were transferred to continuous light shortly before moulting to the last instar (as day 4 larvae in the last stadium or day 1 pupae). Generally, the density of eupyrene sperm bundles on day 10 of adult development was about 2–2.5 times higher in males in continuous light then those under long day conditions. The results presented here indicate that the last larval instar and the pupa are the stages most sensitive to constant light treatment, which greatly reduces the amount of eupyrene sperm bundles released from the testes.     

Ejaculate production schedule and the degree of protandry in fishflies (Megaloptera: Corydalidae)

1. To examine the relationship between male–female emergence patterns and ejaculate dynamics, patterns producing sperm and seminal fluids in male internal reproductive organs, the size of a spermatophore transferred at mating and the fate of spermatophore contents moved into female storage organs were compared among the fishflies (Megaloptera: Corydalidae: Chauliodinae), Parachauliodes continentalis, P. japonicus and Neochauliodes sinensis .
2. Spermatophore contents moved into female storage organs decreased rapidly in P. japonicus and N. sinensis , but hardly at all in P. continentalis . This suggests that the females of the former two species may remate sooner than the latter species as it is known in insects that material remaining in the storage organs mechanically inhibits receptivity to mating.
3. Male P. japonicus and N. sinensis increased in internal reproductive organ mass continuously after adult eclosion, and the spermatophore size produced at the first mating increased with male age. In contrast, the internal reproductive organs of P. continentalis were relatively small and did not increase in mass after emergence. P. continentalis transferred a constantly smaller spermatophore at any copulation than the former two species.
4. Males of P. japonicus and N. sinensis emerged earlier than females, while P. continentalis showed a nearly simultaneous emergence pattern between the sexes. It seems that males of P. japonicus and N. sinensis (more polyandrous than P. continentalis ) inhibit female receptivity for a longer time period by emerging earlier and transferring larger ejaculates. In these two species, the number of sperm ejaculated at the first mating also increased with male age. The increase in sperm number by emerging earlier may be adaptive for the males owing to numerical sperm competition when the female remates.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly, Delia antiqua: the change of rhythmicity

When pupae of Delia antiqua were transferred to constant darkness (DD) from light-dark (LD) cycles or constant light (LL), the sensitivity to light of the circadian clock controlling eclosion increased with age. The daily rhythm of eclosion appeared in both non-diapause and diapause pupae only when this transfer was made during late pharate adult development. When transferred from LL to DD in the early pupal stage, the adult eclosion was weakly rhythmic in non-diapause pupae but arrhythmic in diapause pupae. However, the sensitivity of the circadian clock to temperature cycles or steps was higher in diapause pupae than in non-diapause pupae; in the transfer to a constant 20 degrees C from a thermoperiod of 25 degrees C (12 h)/20 degrees C (12 h) on day 10 after pupation or from chilling (7.5 degrees C) in DD, the adult eclosion from diapause pupae was rhythmic but that from non-diapause pupae arrhythmic. In a transfer to 20 degrees C from the thermoperiod after the initiation of eclosion, rhythmicity was observed in both types of pupae. The larval stage was insensitive to the effect of LD cycle initiating the eclosion rhythm. In D. antiqua pupae in the soil under natural conditions, therefore, the thermoperiod in the late pupal stage would be the most important 'Zeitgeber' for the determination of eclosion timing.     

玉米螟赤眼蜂雄性生殖力的研究

根据膜翅目寄生蜂未受精的卵发育为雄性个体,受精卵发育成雌性个体这一性别决定机制,考察了玉米螟赤眼蜂雄蜂生殖力的大小,探讨了雄蜂授精能力与个体大小、年龄及交配次数之间的关系。结果表明,玉米螟赤眼蜂雄蜂在羽化时或羽化后很短的时间内其精巢就已发育成熟,成虫期不再形成新的精子。雄蜂在羽化后立即可与雌蜂进行交配,在雌蜂过量的情况下,24 h内就可能将体内的精子或精液消耗尽,24 h后的雄蜂虽能与雌蜂继续交尾,但雌蜂所繁育的子代中未见有雌性个体。同一雄蜂能与多头雌蜂进行交尾,授精8～23头雌蜂,平均能繁育出346.15头雌性后代。雄蜂的授精能力与交配次数密切相关,授精量随交配次数增加而逐渐下降。首次交配时,雄蜂能给雌蜂提供较多的精子,约能繁育出58.85头雌性后代,但随着交配次数的增加,雄蜂向雌蜂输送的精子越来越少,10次交配之后,雄蜂所能授精、繁育的子代雌性数将不超过10头。以后足胫节长度表示个体大小时,体型较大的雄性个体进行多次交配的能力强,能繁育更多的雌性后代。     

蛇莓跳甲的生物学初步观察

蛇莓跳甲Alticafragariae(Nakane)是一种寡食性昆虫,在北京地区世代重叠现象明显,1年可发生2~3代,以成虫越冬,越冬时有明显的群集行为。蛇莓跳甲幼虫共3个龄期。在实验室条件下(光照∶黑暗=16∶8,25℃),蛇莓跳甲卵期为7~9d,平均7.57d;从幼虫孵出开始到羽化需要20~24d,其中雄虫平均需要21.31d,雌虫平均需要21.73d,羽化率为79%,羽化后5~7d可达到性成熟,开始交配、产卵。     

Male diet and age influence to inhibit female remating in Ceratitis capitata (Diptera: Tephritidae)

This study evaluated the influence of age and adult nutritional status of Ceratitis capitata males on their ability to inhibit female remating. Their roles and that of copula duration on the amount of sperm transferred to female spermathecae were also analysed. After emergence, adults were kept in separate groups according to their diets (either high protein – 6.5 g of brewer’s yeast, or low protein – 3.5 g of brewer’s yeast) and their age at the time of use in experiments (4, 8, 12, 16 and 20 days old). The results demonstrated that: (i) male age was not a factor that influenced remating when females mated with well‐nourished males; however, the youngest males (4 days old) in the low‐protein group were less efficient in preventing female remating; (ii) 12‐ and 16‐day‐old males fed on a high‐protein diet transferred and produced more sperm than males of other groups; (iii) there was no correlation between copula duration and the amount of sperm transferred to the female; the longest copula durations were observed among low‐protein‐diet/20‐day‐old males. These results suggest that age and nutrition influence the ability of the males to inhibit female remating. The sterile insect technique is most effective when females do not remate after coupling with sterile males, and therefore, the capacity to inhibit female remating is an important characteristic of males released in the field.     

Patterns of Sperm Transfer in the Golden Orb‐Weaver Nephila edulis

Sperm competition studies typically identify copulation duration as an important predictor of paternity as it may determine the quantity of sperm transferred and thus paternity success. This study explores the relationship between copulation duration, male body size, male age and sperm transfer in the golden orb‐weaving spider, Nephila edulis. Paternity in this species is strongly associated with the relative frequency and duration of copulation, which is also influenced by male size. We determined the number of sperm transferred during copulation, by performing sperm counts in both the male copulatory organs (palps) and female sperm receptacle (spermatheca) of recently mated pairs. The total number of sperm recorded (the sum in the male palps and female spermathecae) was greater for younger males than older males, but did not vary with male body size. In general, younger males transferred more sperm and a greater proportion of their sperm supplies than older males and, among these younger males, larger individuals transferred more sperm. However, there were no significant size effects for older males. More sperm was transferred with longer copulations, but in contrast with previous studies, we found that larger males copulated for longer. The rate of sperm transferred was negatively correlated with the duration of copulation, suggesting that the variation in copulation duration in N. edulis may represent strategic investment by males to alter patterns of paternity, in addition to transferring additional sperm.     

Larval development of Diploptera punctata reared alone and in groups

Larvae of the cockroach Diploptera punctata were reared in isolation, in pairs, or in groups of 8–10. Duration of larval development, age at each ecdysis, weights at birth and ecdyses, and adult head-capsule width were measured. Duration of larval development was longer and adult size was larger in isolated animals than in animals reared in pairs and groups. The effect of isolation on development was more pronounced in males. All females had 4 larval instars, whereas males had 3 or 4 instars. The proportion of males with 4 larval instars was higher among animals reared in isolation. There was no difference in the duration of larval development or adult size between pair- and group-reared animals. The sex of animals in the group did not affect adult size or the duration of larval development. Males which underwent 3 or 4 larval instars had different schedules of moulting. Rates of growth of males of both instar types reared in isolation and pairs were similar. Greater adult weight of isolated animals and 4-instar-type males was a result of their longer duration of larval development. Both a higher rate of growth and longer duration of larval development contribute to the larger adult size of females than males.     

Ecdysteroid titres during postembryonic development of Sarcophaga bullata (Sarcophagidae: Diptera)

The level of ecdysteroids in Sarcophaga bullata was determined by radioimmunoassay (RIA) from the time of larviposition (0 hr) until adult eclosion. Five distinct peaks of ecdysteroid activity were recorded. The first two, which occurred midway through the duration of the stadia (14 and 30 hr, respectively), resulted in larval/larval moults (24 and 44 hr). The third peak of ecdysteroid activity commenced at 131 hr and was associated with formation of the white prepuparium. The fourth peak was sustained over a long time period (from 79 hr post pupariation to 120 hr) and resulted in pupal/adult apolysis and the definition of the adult form. The last elevation of the ecdysteroid titre at approx. 160 hr post pupariation) was associated with the synthesis and secretion of adult cuticle.     

Age-Related Sperm Production,Transfer, and Storage in the Sweet Potato Weevil, <Emphasis Type="Italic">Cylas formicarius</Emphasis> (Fabricius) (Coleoptera: Curculionidae)

The relationship between sperm production, insemination rate, and sperm transfer were studied in the sweet potato weevil, Cylas formicarius. Older adult males retained more sperm in the testes-seminal vesicle complex (TSC) and thus more was ejaculated into females at first mating. Number of matings per day for males was relatively constant across different ages, and frequent mating resulted in a reduced amount of sperm transferred to females, especially in young males. Young virgin males had a relatively small ejaculate, and almost all sperm transferred to females was stored in the spermatheca, whereas older virgin males transferred a larger amount of sperm to females, in whom sperm was found in both the spermatheca and post-spermathecal organs (PSO) after mating. The number of sperm in the PSO decreased markedly within 24 h after mating, but amounts in the spermatheca remained the same. Just where the sperm in the PSO went is a point that remained undetermined. The amount of sperm in the spermatheca was reduced more rapidly in females that laid eggs than in females that did not, although sperm reduction occurred even in the latter. Insemination of this weevil corresponded with the volume of the spermatheca, and the amount of sperm stored in the TSC was determined by the age and mating history of the males.     

Effect of gamma-irradiation on some biological activities of the larval stage of the khapra beetle, Trogoderma granarium Everts (Col., Dermestidae)

Abstract: The present study was carried out on the larval stage of the khapra beetle, Trogoderma granarium Everts to determine some biological effects of gamma irradiation at levels between 20 to 100 Gy on various aspects of larval behaviour such as number of moults, developmental time, larval growth, starvation and mortality, pupal promptness in addition to larval density. Larval mortality of 92.5% was obtained by treating with 80 Gy and no larva lived after an exposure of 100 Gy or more. With increasing doses from 40 Gy or more, half of the male and female larvae had six moults as compared with three to five moults in the control. The larval duration increased gradually and reached 40.2 days for male larvae and 44.2 days for female ones at a dose of 80 Gy as compared to 25.2 and 28.3 days, respectively, for the control. Larvae irradiated with 60 and 80 Gy did not feed as much as those irradiated at 20 and 40 Gy or the control group. A negative correlation was observed between increasing dosage levels and reduction in the fresh body weight of larvae. The highest larval starvation of 79.8% occurred at 80 Gy and the least (23.8%) at 20 Gy. Pupal promptness seems to be lower at the higher radiation doses. With 40, 60 and 80 Gy, approximately 69.5, 19.6 and 7.5%, respectively, of the larvae succeeded in pupation compared with 94.6% in the control. High doses of radiation seem to enhance the production of males. An increase of larval density enhances the effects of radiation doses to retard the developmental time, to increase larval and pupal mortality and to reduce adult eclosion.     

The mating-induced refractoriness of Lucilia cuprina females: manipulating the male contribution

Abstract Three manipulations of the male contribution to copulation were used to investigate what determines the switch-off of female receptivity that follows mating in Lucilia cuprina. Multiple matings by males led to a reduction in their effectiveness at switching-off females: the first twelve matings caused more than 50% of females to be switched-off 1 day after mating, while the first four matings caused more than 50% of females to be switched-off for 7 days after mating. Males mated up to twenty-three times and on average ten times during 10 h of continuous access to virgin females. The number of sperm transferred declined logarithmically through a series of matings as did the quantity of material transferred from the male accessory gland (measured as radiolabeled material) through the first six matings. Overnight isolation of multiply-mated males led to considerable recovery of their ability to switch-off females, and to limited renewal of their ability to transfer sperm. Castrated males transferred similar quantities of accessory gland material to females as did sham-operated males during their first five matings and in their first three matings switched-off 95% of females for 1 day but only 48% for 7 days. When normal mating pairs were separated at increasing intervals after coupling, an increasing proportion of females were switched-off at 1 or 7 days afterward. 7 days after 2 min matings no females were switched-off though 40% of the number of sperm transferred in a full mating had been transferred by this time. The proposed explanation for these data is that both the initial switch-off and its duration are determined by the quantity of a receptivity-inhibiting substance that normally enters the female haemo-lymph after being injected by the male into the wall of the bursa copulatrix. It is proposed that when castrated males mate, an absence of sperm results in most accessory gland secretion entering the empty spermathecae (rather than the wall of the bursa as usually occurs) and hence being unable to reach the haemolymph and exert its influence. The effective dose of the receptivity-inhibiting substance is measured on a logarithmic scale.     

Presence of a single abundant storage hexamerin in both larvae and adults of the grasshopper, Schistocerca americana

We identified a single hexameric storage protein in the grasshopper, Schistocerca americana, and monitored its abundance through the last larval instar and up until reproductive competence in adults of both sexes. This storage hexamerin, termed Schistocerca americana Persistent Storage Protein (saPSP) was the most abundant soluble protein in both larvae and adults. In both sexes, saPSP abundance started out low at the onset of the last larval instar and accumulated during feeding, peaking just prior to molting. Adults of both sexes contained significant amounts of saPSP after eclosion. In adult males, saPSP content dropped continuously after eclosion and was lowest once individuals reached reproductive maturity. In contrast, adult females depleted saPSP reserves during the first days of adulthood, but subsequently accumulated significant saPSP stores. In adult females, saPSP stores peaked just prior to the completion of egg provisioning. Given the overall patterns of abundance, saPSP has functions in both larvae and adults. In addition, the observed pattern of storage hexamerin accumulation differs from patterns of accumulation in the other known grasshoppers, Locusta migratoria and Romalea microptera, suggesting that significant functional diversity has evolved in storage hexamerins among the grasshoppers.     

Influence of photoperiod on low temperature acclimation for cold-hardiness in Drosophila auraria

ABSTRACT. Imagines of Drosophila auraria Peng, a reproductive diapause species, developed cold-hardiness at low temperatures to a greater extent when exposed to a diapause-inducing photoperiod (LD10:14 h) than when exposed to a diapause-preventing photoperiod (LD 16:8h). Imagines kept at 18°C, which was the temperature at which they were reared to eclosion, did not survive a test exposure to -5°C for 8 days regardless of age or photoperiod. When transferred to 10 or 5°C, either from eclosion or from 8 days after eclosion, the survival rate, on testing, rose with time since transfer and rose faster and higher with a photoperiod of LD 10:14h than with LD16:8h. Flies transferred to 15°C only showed improved ability to survive the test if they were kept in LD 10:14h. When cultured at 18°C to the age of 8 days after eclosion, diapause was terminated in about 30% of females even at LD 10:14h. In these post-diapause females the ability to develop cold-hardiness at lower temperatures was somewhat less than in the diapausing females, but apparently greater than in the non-diapause females. These results suggest that the physiological mechanism which promotes cold-hardiness under a diapause-inducing photoperiod is not directly linked to the process causing reproductive diapause.
In Sapporo, flies from a natural population became tolerant to cold in October when they entered diapause and daily mean temperature fell below 15°C and the light/dark cycle fell below LD 12:12h.     

Temperature-dependent ovariole and testis maturation in the yellow dung fly

Temperature is one of the abiotic environmental factors most strongly affecting animal behaviour, physiology, and life history. In insects, lower temperatures generally slow down most physiological processes, reducing growth rate and prolonging the juvenile period. Here, we investigate temperature‐dependent ovariole and testis maturation in the anautogenous yellow dung fly, Scathophaga stercoraria L. (Diptera: Scathophagidae), and relate it to corresponding temperature effects on pre‐adult development time and the adult pre‐reproductive period. Flies were reared in the laboratory at three constant temperatures (18, 22, and 26 °C), and the size of the developing ovarioles and testes (reflecting sperm production) was measured over time (i.e., age). Ovariole size increased asymptotically over the first 12 days of adult life, while the testes continued to fill after day 10. In accordance with the temperature‐size rule, warmer temperatures resulted in smaller ovarioles (eggs) and smaller testes, independent of body size. Warmer temperatures also greatly reduced pre‐adult development time by more than half, from 12 to 25 °C, the larger males always taking 1–3 days longer than the females. Corresponding temperature effects on the adult pre‐reproductive period were small (<1 day between 15 and 25 °C), with males taking 5–6 days and females 10–13 days to first reproduction. Time lost by males during the pre‐adult stage, when ovaries and testes are produced, can thus be more than compensated‐for by time gained during the pre‐reproductive period, when eggs and sperm are produced, so males can nevertheless start reproducing sooner than females.