Uptake and loss of water in diapause and non-diapause eggs of crickets

ABSTRACT. In laboratory-laid eggs of the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), water absorption occurs at an early stage of embryogenesis (stage II) at 30°C but is delayed until later stages at lower temperatures. This is related to the variation in diapause stage at different temperatures. No egg developed beyond stage VII (the end of anatrepsis) without water absorption.
A. fasciatus shows seasonal variation in the stage of water absorption. At 30°C, eggs collected in August absorb water at the early stage while many of those collected in September avert diapause and absorb water at a later stage.
Diapause also influenced the water absorption of eggs in A. socius Scudder. Eggs of short-day females enter diapause and absorb water at stage II, while those of long-day females develop without diapause and absorb water at a later stage (around stage IV).
The susceptibility to desiccation (r.h. 50%) was examined at 20°C with A. fasciatus eggs. The percentage water loss and mortality of eggs varied with the time and duration of exposure to desiccation. Eggs are most sensitive to desiccation during the first several days after being laid and during the period of water absorption.     

Quantitative food utilization and reproductive allocation by adult milkweed bugs, Oncopeltus fasciatus

ABSTRACT. Age-specific and lifetime dry mass budgets were estimated for mated and virgin adult milkweed bugs, Oncopeltus fasciatus (Dallas) Hemiptera: Lygaeidae), fed air-dried milkweed seeds ( Asclepias syriacd ) in the laboratory at LD 14:10 and 23°C. Relative consumption rate (RCR) of all bugs was high during the first 8 days posteclosion (teneral period) as their fresh weight, dry weight, and fat content increased. Thereafter, the physiological syndrome associated with reproduction in mated females was indicated by their higher RCR, earlier and greater rate of egg production, greater lifetime relative metabolic rate and higher net and gross production efficiencies than virgin females and males. Males tended to live longer than virgin and mated females, which had similar lifespans. Mated females weighing less at eclosion remained lighter in weight on the day of mean peak weight, but food consumption, egg production and lifespan were independent of body-weight over a 25% range. Input of nymphal reserves or male reproductive secretions to egg production is probably minor in comparison with the adult female's food budget. The high proportion of the food budget allocated to egg production by mated females of O.fasciatus is consistent with its migratory, colonizing lifestyle.     

Delayed mating reduces fecundity of blackheaded fireworm, Rhopobota naevana, on cranberry

This study examines the effects of delayed mating on two successive generations of blackheaded fireworm, Rhopobota naevana Hübner (Lepidoptera: Tortricidae), a pest of cranberry, Vaccinium macrocarpon Aiton (Ericaceae). The first (spring) generation produces eggs that hatch soon after oviposition, whereas the second (summer) generation produces mostly diapause eggs. Unmated female and male moths were placed together on the first, second, fourth, sixth, or eighth day after emergence. In the first generation, incidence of mating was greatest in the 1-, 2-, and 4-day treatments then declined as female survival decreased. In the second generation, incidence of mating was lowest in the 1-day treatment and greatest in the 2-, 4-, and 6-day treatments. Most second generation females in the 6- and 8-day treatments survived to mate. The mean oviposition period was 2.6 days for first generation females and 4.1 days for second generation females. Fecundity of singly mated females in both generations declined as age at mating advanced, but the pattern of decline differed between generations. First generation females that were mated on the first or second day laid more eggs than those mated on the fourth, sixth, or eighth day, and the number of infertile eggs increased as age at mating advanced. Fecundity of second generation females declined more gradually and the number of infertile eggs was greatest for females mated on the first, sixth, or eighth day. A consequence of the marked decline in fecundity due to mating delays in the first generation was that mean fecundity of the entire group of first generation females was ca. 13% less than that of the group of second generation females. On cranberry farms, pheromone-mediated mating disruption can prevent or delay mating of blackheaded fireworm. If the frequency of disrupted (prevented and delayed) matings is similar in the two generations, fewer eggs will be laid in the first generation than in the second.     

Seasonal variation in embryonic diapause of the striped ground cricket, Allonemobius fasciatus

ABSTRACT. The incidence and intensity of embryonic diapause in the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), is influenced by the date of oviposition and the incubation temperature. At 20C, embryos develop normally until the end of the appendage-formation stage when diapause occurs. The intensity of 'winter' diapause at this stage is greatest in eggs laid early in the season. Incubation at higher temperature induces a different and earlier 'summer' diapause. The higher the temperature the earlier the stage at which this developmental suppression is imposed. At 27 and 30C, some individuals develop without any interruption and hatch within 20 days. The proportion of these fast-developing eggs is low in summer but increases towards the end of the laying season. In nature, this species is univoltine and precocious hatching before winter is unlikely.
When embryos diapausing at an early stage at 27C are transferred to low temperatures, they resume development and enter winter diapause. The time required to reach the winter-diapause stage after transfer is inversely related to the temperature (30-30C). At 30C, sunmer diapause is neither induced nor maintained.     

Cost of male diapause indirectly affects female reproductive performance

We evaluated the cost of diapause in both females and males separately in the multivoltine bruchid Acanthoscelides pallidipennis (Motschulsky) (Coleoptera: Bruchidae). We artificially generated diapause (D) and non‐diapause (ND) individuals and compared the reproductive traits among all combinations of D and ND pairs. Diapause in both sexes had negative effects on the female pre‐oviposition period and fecundity, but not on egg volume. Females mated to D males had longer pre‐oviposition period and lower fecundity than females mated to ND males. These results showed that reproductive performance of a female could be influenced by the diapause experience not only of herself but also of the male with whom she mated.     

Variations of hydrogen peroxide and catalase expression in Bombyx eggs during diapause initiation and termination

For diapause eggs of the silkworm, Bombyx mori, diapause initiation is prevented with hydrochloric acid (HCl) at around 20 h post-oviposition while diapause status is terminated with chilling around 5°C. To investigate whether hydrogen peroxide (H(2)O(2)) and catalase expression are involved in diapause initiation and termination, the concentration of H(2)O(2), relatively higher levels of catalase mRNA and activity of catalase were compared between (1) 20-h-old diapause eggs and the HCl-treated diapause eggs, and (2) 10-day-old diapause eggs and the 5°C-chilled diapause eggs. Compared to diapause eggs, the HCl-treated eggs had significantly higher H(2)O(2) concentrations (up from approximately 1-3 μmol/g fresh mass to 5-8 μmol/g fresh mass), higher relative level of catalase mRNA (up from 0 to 35.2%) and higher catalase activity (up from 2.51 units/mg protein to 4.97 units/mg protein) at 96 h post-treatment. On the other hand, the 5°C chilling resulted in significant increases of H(2)O(2) concentration (up from 0.79 μmol/g fresh mass to 5.57 μmol/g fresh mass), relative level of catalase mRNA (up from 0 to 71.4%) and catalase activity (up from 0.88 units/mg protein to 3.42 units/mg protein) within 120 days. The results obtained in this work suggest that variations of H(2)O(2) and catalase expression in Bombyx eggs are involved in diapause initiation and termination.     

Environmental Cues, Endocrine Factors, and Reproductive Diapause in Male Insects

Environmental cues, mostly photoperiod and temperature, mediated by effects on the neuroendocrine system, control reproductive diapause in female insects. Arrest of oocyte development characterizes female reproductive diapause, which has two major adaptive functions: It improves chances of survival during unfavorable season(s), and/or it confines oviposition to that period of the year that is optimal for survival of the eggs and progeny. Although reproductive diapause is less well studied in male insects, there may be no sex-dependent differences in regard to the first of these functions. The second one, however, is not valid for the male; instead, selection pressure directs the male's reproductive strategy toward maximum chances of fertilization of the female's eggs with minimum waste of energy. Therefore, in species with female reproductive diapause, the males may or may not exhibit diapause, but if they do, their diapause must be adapted to that existing in conspecific females. Male reproductive diapause is defined as a reversible state of inability of the male to inseminate receptive females. In relation to reproductive diapause, there are several patterns of coadaptations between male reproductive strategy and timing of female receptivity, (a) In some insects, the females are receptive in the early part of their diapause; mating occurs during this period and there is no diapause in the male. The male dies shortly after copulation and the female stores the sperms to fertilize the eggs that develop after termination of the female's diapause, (b) In some species, as in the grasshopper Anacridium aegyptium, females are receptive during diapause; though oocyte development is arrested, copulation occurs and the stored sperms fertilize the eggs when the female's diapause ends. Males were claimed to have no diapause, but recent studies have revealed the presence of a reproductive diapause in a proportion of the males. This and other cases show that female receptivity during reproductive diapause may or may not be accompanied by male reproductive diapause. If there is a reproductive diapause in the male, it is controlled by the same endocrine mechanism, the corpora allata (CA), as in the females, (c) In many species females are refractory during their diapause. In these cases, males exhibit reproductive diapause, which may be light, as in the beetle Oulema melanopus, or well established, as in certain grasshoppers, butterflies, and beetles. In the latter cases, male diapause is controlled by similar environmental cues (photoperiod, temperature) and by the same intrinsic mechanism (neuroendocrine system, especially CA) as female diapause. Nevertheless, male diapause is less intense; the environmental cues leading to its termination are less complex and/or less extreme, so male diapause terminates before that of the females. Presumably, male diapause is under two antagonistic selection pressures: A male should not waste energy by courting dia-pausing refractory females, but he should be ready to copulate as soon as the females become receptive, otherwise he may lose in the competition between males for females. Some further strategies, which do not seem to fit the above patterns, are also outlined.     

A comparison of photoperiodic control of diapause between aestivation and hibernation in the cabbage butterfly Pieris melete

In the cabbage butterfly, Pieris melete, summer and winter diapause are induced principally by long and short daylengths, respectively; the intermediate daylengths (12-13 h) permit pupae to develop without diapause. In this study, photoperiodic control of summer and winter diapause was systematically investigated in this butterfly by examining the photoperiodic response, the number of days required to induce 50% summer and winter diapause and the duration of diapausing pupae induced under different photoperiods. Photoperiodic response curves at 18 and 20 degrees C showed that all pupae entered winter diapause at short daylengths (8-11 h), the incidence of diapause dropped to 82.3-85.5% at 22 degrees C without showing a significant difference between short daylengths, whereas the incidence of summer diapause induced by different long daylengths (14-18 h) was varied and was obviously affected by temperature. By transferring from various short daylengths (LD 8:16, LD 9:15, LD 10:14 and LD 11:13) to an intermediate daylength (LD 12.5:11.5) at different times after hatching, the number of cycles required to induce 50% winter diapause (7.28 at LD 8:16, 7.16 at LD 9:15, 7.60 at LD 10:14 and 6.94 at LD 11:13) showed no significant difference, whereas by transferring from various long daylengths (LD 14:10, LD 15:9, LD 16:8 and LD 17:7) to an intermediate daylength (LD 12.5:11.5) at different times, the number of cycles required to induce 50% summer diapause (5.95 at LD 14:10, 8.02 at LD 15:9, 6.80 at LD 16:8, 7.64 at LD 17:7) were significantly different. The intensity of winter diapause induced under different short daylengths (LD 8:16, LD 9:15, LD 10:14 and LD 11:13) was not significantly different with an average diapause duration of 87 days at a constant temperature of 20 degrees C and 92 days at a mean daily temperature of 19.0 degrees C, whereas the intensity of summer diapause induced under different long daylengths (LD 14:10, LD 15:9, LD 16:8 and LD 17:7) was significantly different (the diapause duration ranged from 75 to 86 days at a constant temperature of 20 degrees C and from 76 to 88 days at a mean daily temperature of 19.0 degrees C). All results suggested that photoperiodic control of diapause induction and termination is significantly different between aestivation and hibernation.     

Effects of diapause on post‐diapause reproductive investment in the moth Ostrinia scapulalis

Diapause is a strategy used by many insect species to survive adverse environmental conditions. However, diapause incurs costs that may have adverse effects on post‐diapause development and reproduction. We herein investigated the effects of diapause on the post‐diapause reproductive investment of males and females in a multivoltine moth, the adzuki bean borer, Ostrinia scapulalis (Walker) (Lepidoptera: Crambidae). We found that (1) post‐diapause males and females were smaller and had lower mating success than non‐diapause individuals, (2) post‐diapause females had lower fecundity and shorter longevity than non‐diapause females, (3) post‐diapause males transferred similar numbers of eupyrene and apyrene sperm as non‐diapause males, (4) the fecundity and longevity of non‐diapause females mated with post‐diapause males and those mated with non‐diapause males were not significantly different, and (5) no significant relationship was found between diapause duration (short and long) and post‐diapause reproductive investments in both males and females. These results suggest that post‐diapause males did not reduce reproductive investment in spite of the cost of diapause, and the significant decline in reproductive output in post‐diapause females was due to their reduced body weight and longevity, which appeared to be direct consequences of the cost of diapause.     

Environmental Cues,Endocrine Factors,and Reproductive Diapause in Male Insects

Environmental cues, mostly photoperiod and temperature, mediated by effects on the neuroendocrine system, control reproductive diapause in female insects. Arrest of oocyte development characterizes female reproductive diapause, which has two major adaptive functions: It improves chances of survival during unfavorable season(s), and/or it confines oviposition to that period of the year that is optimal for survival of the eggs and progeny. Although reproductive diapause is less well studied in male insects, there may be no sex-dependent differences in regard to the first of these functions. The second one, however, is not valid for the male; instead, selection pressure directs the male's reproductive strategy toward maximum chances of fertilization of the female's eggs with minimum waste of energy. Therefore, in species with female reproductive diapause, the males may or may not exhibit diapause, but if they do, their diapause must be adapted to that existing in conspecific females. Male reproductive diapause is defined as a reversible state of inability of the male to inseminate receptive females. In relation to reproductive diapause, there are several patterns of coadaptations between male reproductive strategy and timing of female receptivity, (a) In some insects, the females are receptive in the early part of their diapause; mating occurs during this period and there is no diapause in the male. The male dies shortly after copulation and the female stores the sperms to fertilize the eggs that develop after termination of the female's diapause, (b) In some species, as in the grasshopper Anacridium aegyptium, females are receptive during diapause; though oocyte development is arrested, copulation occurs and the stored sperms fertilize the eggs when the female's diapause ends. Males were claimed to have no diapause, but recent studies have revealed the presence of a reproductive diapause in a proportion of the males. This and other cases show that female receptivity during reproductive diapause may or may not be accompanied by male reproductive diapause. If there is a reproductive diapause in the male, it is controlled by the same endocrine mechanism, the corpora allata (CA), as in the females, (c) In many species females are refractory during their diapause. In these cases, males exhibit reproductive diapause, which may be light, as in the beetle Oulema melanopus, or well established, as in certain grasshoppers, butterflies, and beetles. In the latter cases, male diapause is controlled by similar environmental cues (photoperiod, temperature) and by the same intrinsic mechanism (neuroendocrine system, especially CA) as female diapause. Nevertheless, male diapause is less intense; the environmental cues leading to its termination are less complex and/or less extreme, so male diapause terminates before that of the females. Presumably, male diapause is under two antagonistic selection pressures: A male should not waste energy by courting dia-pausing refractory females, but he should be ready to copulate as soon as the females become receptive, otherwise he may lose in the competition between males for females. Some further strategies, which do not seem to fit the above patterns, are also outlined.     

Effects of diapause duration on future reproduction in the cabbage beetle,Colaphellus bowringi: positive or negative?

Abstract.  Cabbage beetles, Colaphellus bowringi , undergoing an imaginal summer and winter diapause in the soil, show a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25 °C with an LD 14 : 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring's performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female.     

针叶小爪螨的滞育研究

本文研究针叶小爪螨Oligonychus ununguis(Jacobi)滞育卯出现的规律,分析了光照、温度、寄主营养等环境因素与滞育的关系和滞育卵解除的条件。结果表明,针叶小爪螨以滞育卵在枝条上越冬,其产出盛期在8月上、中旬。光周期感应螨态为幼螨至第二若螨的连续两个螨态;其临界光照时间为13h/d。在相同条件下,低温(20℃)促进滞育。长日照下,螨口密度大,寄主营养恶化,亦能促进滞育的形成。滞育卵在0℃下放置1 20天,5℃-10℃下放置100天后解除滞育。     

Differences in the pre‐diapause and pre‐oviposition accumulation of critical nutrients in adult females of the beetle Colaphellus bowringi

In many insect species, the differentiation of development between diapause and reproduction first becomes obvious during the diapause preparation (pre‐diapause) and pre‐oviposition phases. However, the differentiation of nutrient accumulation between these two phases remains unclear. We compared the weights of pre‐diapause and reproductive adult female Colaphellus bowringi Baly (Coleoptera: Chrysomelidae), and measured their triacylglycerol (TAG), protein, and carbohydrate content from emergence until they had fed for 4 days post‐eclosion. We also compared the ovarian development and accumulation of lipid droplets between pre‐diapause and reproductive adult females in order to determine whether we could visually detect differences in nutrient allocation. The weights of both pre‐diapause and reproductive females increased with duration of feeding. The fresh weight and water content of pre‐diapause females was significantly lower than that of reproductive females after feeding for 3 days post‐eclosion. Pre‐diapause females channeled their reserves into TAG in the fat body, whereas reproductive females converted nutrients into proteins and carbohydrates for egg development. These results quantify differences in nutrient accumulation between pre‐diapause and reproductive adult female C. bowringi, and provide clues for understanding the molecular mechanisms underlying differences in the allocation of nutrients between diapause and reproduction in insects.     

A maternal effect that eliminates pupal diapause in progeny of the flesh fly, Sarcophaga bullata

Flesh flies that have experienced pupal diapause produce progeny that will not enter diapause even when reared in a strongly diapause-inducing environment. The effect is determined, not by diapause itself, but by the short days previously received by the larvae during the programming of pupal diapause. Reciprocal cross matings indicate that the effect is transmitted solely by the female parent. Though the embryos develop within the uterus of the female, the maternal effect is transmitted prior to the onset of embryogenesis, probably during oögenesis. Only by rearing a generation in long-day (nondiapausing) conditions can the capacity for pupal diapause be restored in the progeny. The effect is likely to provide an adaptive mechanism for preventing an untimely diapause response among the progeny of overwintering females that emerge early in the spring.     

Reversible change in embryonic diapause intensity by mild temperature in the Chinese rice grasshopper, Oxya chinensis

The effects of temperature on maintenance and termination of embryonic diapause were investigated in Jining (35.4°N, 116.6°E) and Sihong (33.5°N, 118.2°E) strains of the Chinese rice grasshopper, Oxya chinensis Thunberg (Orthoptera: Catantopidae). Eggs of both strains entered diapause when incubated at 30, 25, or 20 °C. Chilling at 8 °C had an evident effect on diapause termination and almost all eggs chilled for 60 days ended diapause development. Chilling of eggs at 8 °C for only 20 days failed to result in any hatching at 20 °C, suggesting that such level of chilling was not enough to induce diapause termination. However, the treatment combining incubation of eggs at 30 °C for varying lengths of time with subsequent incubation to 20 °C had a distinct effect on the completion of diapause of the eggs. The results indicate that there were two temperature optima, that is, low temperature (chilling) and high temperature, for diapause development in this grasshopper species. Incubation of chilled eggs at 20 °C for 5–15 days followed by further incubation at 25 °C reduced termination of diapause significantly compared with the eggs only chilled at 8 °C. Exposure of eggs chilled at 8 °C to a pulse of 25 °C from 1 to 7 days, separated by a 20-day interval at 8 °C, resulted in a decrease in the percentage of successfully hatched eggs as the length of the pulse of 25 °C increased. The results suggest that diapause intensity may be restored at moderately high temperatures. This reversible change in diapause intensity would play an important role in maintaining diapause before winter.     

Identification, characterization, and developmental regulation of two storage proteins in the bamboo borer Omphisa fuscidentalis

Two insect storage proteins, OfSP1 (75 kDa) and OfSP2 (72 kDa), were purified using three different chromatographies from the hemolymph of Omphisa fuscidentalis larvae during diapause, and their genes were cloned. OfSP1 and OfSP2 concentrations in the hemolymph were high during diapause. During pupation, OfSP1 levels decreased in the male hemolymph and disappeared from the female hemolymph. OfSP1 and OfSP2 mRNA levels in the fat bodies were low during the third instar, but increased greatly during the fourth and fifth larval instars. During diapause, mRNA expression continued at a lower level than during the feeding period. The injection of 20-hydroxyecdysone (20E) into diapausing larvae caused an increase in OfSP1 and OfSP2 mRNA levels 2-3 days post-injection, followed by a decrease in expression until pupation, which occurred 2-4 days thereafter. When larvae were treated with juvenile-hormone analog (JHA), OfSP1 and OfSP2 mRNA levels gradually decreased until the onset of pupation. In Omphisa, OfSP1 and OfSP2 proteins are produced and released by the larval fat bodies in the fourth and fifth-instar larvae, and the proteins accumulate in the hemolymph until the insects enter diapause. OfSP1 may be reabsorbed by the fat bodies at the end of diapause for subsequent re-use during pupation.     

Effects of temperature of adults and eggs on the induction of embryonic diapause in the band-legged ground cricket, Dianemobius nigrofasciatus

Abstract.  Eggs laid by adult female Dianemobius nigrofasciatus , reared under long-day (LD 16 : 8 h, 25 °C) or short-day (LD 12 : 12 h, 25 °C) conditions from the nymphal stage, are kept at several constant temperatures. At 22.5–30.0 °C, eggs laid by long-day adults show lower incidences of diapause than those laid by short-day adults. In both eggs laid by adults under long-day conditions and those under short-day conditions, the higher the temperature at which the eggs are kept, the lower the incidence of diapause. When eggs of long-day adults are exposed to a low-temperature pulse (10 °C, 24 h) on the day of deposition (day 0), the incidence of diapause increases. The low-temperature pulse on day 1 does not increase the incidence of diapause. By contrast, when the eggs of short-day adults are exposed to a high-temperature pulse (35 °C, 24 h) on day 0 or day 1, the incidence of diapause decreases. The temperature pulses on day 0 are more effective at diapause prevention. Staining of diapause eggs by the Feulgen–Rossenbeck method shows that the eggs enter diapause at the blastoderm stage, which is on day 1 or day 2 at 25 °C. The exposure of adults to long days and higher temperatures prevents the eggs from entering diapause. In D. nigrofasciatus , embryonic diapause is controlled by maternal effects, adult photoperiod and temperature, and egg temperature before or at diapause.     

Diapause hormone directly stimulates the prothoracic glands of diapause larvae under juvenile hormone regulation in the bamboo borer,Omphisa fuscidentalis Hampson

Larval diapause in many lepidopteran insects is induced and maintained by high juvenile hormone (JH). In the case of the bamboo borer, Omphisa fuscidentalis, the effect of JH is the opposite: The application of juvenile hormone analog (JHA: S‐methoprene) terminates larval diapause, unlike in other insect species. Here, we analyzed the expression of JH‐receptor Met, DH‐PBAN, and Kr‐h1 in the subesophageal ganglion (SG) from October to April using semi‐quantitative polymerase chain reaction (PCR). The results show that OfMet and OfDH‐PBAN messenger RNA in the SG are mainly expressed during the larval diapause stage, while OfKr‐h1 increases during the pupal stage. Using tissue culture techniques and an enzyme‐linked immunosorbent assay (ELISA), diapause hormone (DH) was found to induce ecdysteroidogenesis in the culture medium of the prothoracic gland (PG) after incubation for 30 min with 25 ng and 50 ng of DH. Thus, DH is a novel stimulator for the PG. We identified a DHR homolog in the bamboo borer and confirmed that it is expressed in the PG. In addition, for in vitro experiments, DH increased the expression levels of OfDHR, OfEcR‐A, and ecdysone‐inducible genes in the PG. These results demonstrate that DH can function as a prothoracicotropic factor, and this function of DH might be through of DHR expressed on PG cells. Consequently, DH is one of the key factors in larval diapause break which is triggered by JH in the bamboo borer, O. fuscidentalis.     

Effects of photoperiod and temperature on reproductive diapause in Ophraella communa (Coleoptera: Chrysomelidae), a potential biocontrol agent against Ambrosia artemisiifolia

Abstract To investigate the seasonal adaptation strategies of Ophraella communa to new habitats, the effects and regulation mechanisms of photoperiod and temperature on the reproductive diapause in a population collected from Changsha, Hunan were examined. Adults showed obvious reproductive diapause, which was regulated by photoperiod and temperature. At 30°C, there was no adult diapause occurring under either long‐day or short‐day conditions; at 25°C the pre‐oviposition period was short and fecundity was high in adult females under L : D 16 : 8 h, whereas under L : D 12 : 12 h, a few females entered reproductive diapause; at 20°C under short‐day conditions, all female adults entered diapause. The pre‐oviposition period was significantly prolonged when the pupae and adults were transferred from long‐days to short‐days, but the day length influence was not obvious when they were transferred only in the adult stage. However, the fecundity dropped greatly no matter whether the photoperiod shifted to short‐days only in the adult stage or whether the shift occurred in both the pupal and adult stage. The fecundity was extremely low when photoperiod shifted from long‐days to short‐days in both pupal and adult stages. This was an indication that the pupal and adult stages were the photoperiod‐sensitive stage for adult reproductive diapause. This was especially true for the photoperiod in the pupal stage, which has a distinctly significant regulative effect on reproductive diapause. Additionally, this article also addresses the reason for different photoperiodic response patterns in reproductive diapause induction between the Changsha strain and the Tsukuba strain (Japan) of O. communa.     

The effects of temperature on development of the large narcissus fly (Merodon equestris)

Eggs, larvae, pupae and adults of the large narcissus fly (Merodon equestris) were reared at a series of constant temperatures between 9–24°C. Egg development required from 37 days at 9°C to 7 days at 21.5°C. The low-temperature threshold for development was 6.7°C. Larvae reared at 1424°C were fully-grown after 18 weeks, but it took much longer for such insects to pupate, and adult flies emerged only after about 45 weeks of development. Large narcissus flies enter diapause during the larval stage and overwinter as fully-fed larvae, forming pupae in the following spring. Post-winter pupation and pupal development took from 169 days at 10°C to 36 days at 21.5°C. Of this, pupal development required from 91 days at 10°C to 19 days at 21.5°C. The low-temperature threshold for post-winter pupation and pupal development was 7.1°C, and for pupal development alone, 7.2°C. Females maintained at or below 19°C laid few eggs, whereas some females kept at or above 21.5°C laid more than 100 eggs (mean 69 ± 36). Approximately 50% of females maintained at or above 21.5°C laid less than 10 eggs during their lifetime. The mean egg-laying time was 6 to 9 days. Although temperatures at or below 19°C inhibited mating, once a female had mated, such temperatures did not prevent oviposition.