Physiological correlates to courtship, mating, ovarian development and maternal behaviour in the ring-legged earwig

Abstract. The involvement of the endocrine system in courtship, mating, maternal behaviour and the gonadotrophic cycle was studied in the earwig, Euborellia annulipes, after application of JH III and, alternatively, precocene II. Topical application of 35 or 122 μg of JH III to newly eclosed females advanced the onset of courtship behaviour from 6.6 ± 1.3 days in acetone-treated controls to 1.4 ± 2.8 and 0.5 ± 2.5 days, respectively. Application of 6 μg of JH III had no effect on the onset of courtship behaviour. Applications of Juvenile Hormone had no significant effect on the age at first mating nor on the duration of mating, though the trend is towards advanced onset. The age at first oviposition was advanced by hormone treatment; clutch size and the proportion of offspring hatching was reduced by hormone treatment. The interclutch interval, size and proportion hatching of the second clutch were not affected by hormone treatment. Topical application of 50 μg of JH III to females on the day of oviposition shortened the total duration of maternal care from 15.4 ± 0.5 to 5.3 ± 1.7 days; whereas in acetone-treated and precocene II-treated groups maternal care lasted 16.1 ± 1.9 and 13.8 ± 1.6 days, respectively. The duration of maternal care was positively correlated with number of offspring hatching and fledging. In a corollary experiment, topical application of JH III significantly enhanced the onset of the second gonadotrophic cycle as assessed by basal follicle length; application of 20 μg of precocene II, either singly or in repeated doses, did not delay growth of basal follicles. Finally, repeated application of as much as 80 μg of precocene II had no effect on basal follicle length, nor on ovary wet weights. These results are consistent with the hypothesis that intermediate to high titres of JH are associated with oocyte growth, mating, and the cessation of maternal care; low titres of JH appear to be associated with the period of maternal behaviour and slow ovarian follicle development.     

Maternal behavior and clutch manipulation in the ring-legged earwig (Dermaptera: Carcinophoridae)

The expression and maintenance of maternal behavior in the earwig,Euborellia annulipes, was examined through manipulation of clutch size, age, and species and through observations of interactions between brooding females. Females underwent discrete gonadotrophic cycles culminating in oviposition of first clutches that were highly variable in size. Neither the head capsule width nor the age of the mother was correlated with clutch size. Maternal care extended through embryogenesis and for the week following hatching. Clutch removal significantly shortened the interclutch interval, indicating that the presence of brood inhibited the onset of the second gonadotrophic cycle. Brooding females readily accepted replacement clutches of the same age. Thus, mothers did not appear to distinguish their own eggs from those of other females. Experimental doubling of clutch size did not significantly reduce the proportion hatching or fledging. In contrast, reducing clutch size diminished the percentage successfully fledging. Manipulation of clutch age resulted in reduced hatching/fledging success. Placing two females, each with newly laid clutches, in the same cage usually resulted in egg transfer from the nest of one female to that of the other within 12 h. Nests of females with larger forceps were significantly more likely to contain both clutches. When mothers with first clutches were paired with mothers with third clutches, eggs were more likely to be transferred to the nest of the older female.E. annulipes females with newly laid clutches appeared to accept as replacement clutches eggs of the earwigDoru taeniatum. Alien clutches were maintained for the typical duration of embryogenesis; however, noD. taeniatum hatchlings were observed.     

The effect of ventral nerve cord severance and male castration on female mating behavior, clutch size, and maternal care in the ring-legged earwig

Mating is critical for the expression of oviposition and maternal care in the earwig, Euborellia annulipes; additionally, mating diminishes receptivity to additional mating and promotes a decline in juvenile hormone synthesis at the end of the gonadotrophic cycle (in contrast to most insect species wherein mating stimulates juvenile hormone production). We report here that severance of the ventral nerve cord of virgin females similarly promoted egg deposition and maternal care of eggs, diminished mating receptivity, and elicited a timely decline in juvenile hormone biosynthesis. Mating of intact females to adult males that were castrated as larvae did not abolish oviposition; however, clutch size was reduced, and no eggs developed. Such castrated males had smaller seminal vesicles than did intact males, presumably attributable to lack of sperm in castrated males. In contrast, mating of intact females to males castrated on day 1 of adult life did not reduce clutch size compared with those of sham-operated animals and did not abolish fertilization; in fact, these castrated males produced viable offspring after six matings. These results are consistent with the notion that ventral nerve cord severance mimicked mating in intact animals. Following mating, the ventral nerve cord likely is a conduit to release the brain from inhibiting oviposition and maternal care. The presence of sperm in the spermatheca is not necessary for release of this inhibition but may modulate clutch size.     

Juvenile hormone-induced break and termination of diapause in the Colorado potato beetle

Topical applications of Cecropia juvenile hormone I (JH) and several analogues, 1 day after the initiation of diapause, induce a break in diapause 8 to 10 days later, characterized by emergence from the soil, feeding, mating, and reproduction. Activation is only temporary when beetles are kept in short-day photoperiods. The percentage of beetles activated and the duration of activation depend on the nature of the JH and the dose applied. JH application during prediapause only postpones diapause, whereas beetles which have spent 2 months in diapause are activated rather easily. Diapause is completely terminated when JH application is accompanied by a transfer of the beetles to long-day conditions. Thirty μg JH applied to allatectomized females in long-day conditions allows them to reproduce for over 50 days.The extent to which the endocrine system is involved in activation has been investigated. Allatectomy does not change JH-induced activation at long or short daylengths. Volumetric measurements indicate that the corpora allata remain inactive as long as measurable amounts of JH circulate in the blood. An increase in corpus allatum activity after day 8 further stimulates long-day oviposition. Gomoripositive neurosecretory cells in the brain are activated by JH within 1 day. The hypothesis is advanced that a JH-induced break or termination of diapause is mediated through the neuroendocrine system.     

Juvenile hormone and reproduction in crickets, Gryllus bimaculatus De Geer: corpus allatum activity (in vitro) in females during adult life cycle

ABSTRACT. Incubation conditions were established for a short-term radiochemical assay of spontaneous juvenile hormone (JH) biosynthesis in vitro by corpora allata from adult female Gryllus bimaculatus. The only JH synthesized was shown by HPLC to be JH III. A further incubation product, predominantly extracted from the corpora allata, was thought to be the JH III precursor, methyl farnesoate. In adult females reared at a constant temperature of 27°C the synthetic activities of the corpora allata-corpora cardiaca complexes in vitro increase from almost zero to a high peak value 4 days after the imaginal moult. Thereafter the activity decreases to varying intermediate levels, but always lower than the first maximum. Two days after the first peak in corpus allatum activity, ovarian fresh weight increases dramatically and the first oviposition occurs 2 days later.
Topical application of JH III to females reared at 20°C, which usually have a low fecundity, causes a dose-dependent stimulation of egg production and oviposition.     

Effects of chilling stress on allatal growth and juvenile hormone synthesis in the cockroach, Diploptera punctata

During the ovarian cycle of the cockroach, Diploptera punctata, a mitotic wave occurs in the corpora allata before an increase in gland volume and juvenile hormone (JH) synthesis. Previous studies have demonstrated that the brain inhibits mitosis and JH synthesis in corpus allatum (CA) cells until adult females have mated. Herein, we report that chilling stress effectively suppresses mating induced proliferation of CA cells. In mated females, chilling on melting ice for 0.5-3 hours caused a strong, dose-dependent decrease in mitotic activity. In insects chilled for 3 hours, although the mitotic wave in the CA was practically abolished, CA volume and JH synthesis finally reached peak levels typical of unchilled insects, despite a 2-day delay. Consequently, oocyte maturation and oviposition were also delayed by 2 days, yet in both chilled and unchilled insects, peak values of basal oocyte length were the same. By allowing virgin females to mate on different days after chilling, we found that the chilling effect could be retained in the insect body for at least 2 days. During this period, signals from mating could not effectively remove inhibition of CA cell proliferation. Unilaterally disconnecting the CA from the brain revealed that chilling stress mediated CA cell proliferation via the brain, and did not directly affect the CA.     

Biosynthesis and release of juvenile hormone during the reproductive cycle of the ring-legged earwig

Corpora allata of adult female Euborellia annulipes, incubated in medium containing ³H-methionine, synthesized and released juvenile hormone III. Labelled material co-migrating with methyl farnesoate was also found, suggesting this as an intermediate in the pathway of juvenile hormone III production. Juvenile hormone was not appreciably stored in the glands, but was released into the medium. In normal medium, 93.6 ± 1.6% of the total juvenile hormone III synthesized was released and 96.5% ± 0.3 in medium supplemented with 60 μM farnesoic acid. The rate of juvenile hormone III biosynthesis/release in vitro remained constant for at least 8 hr for glands of different activities. The rate of juvenile hormone production was closely correlated with the gonadotrophic cycle. In females with previtellogenic ovarian follicles (0.26 ± 0.004 mm), hormone production was only 0.59 ± 0.13 fmol hr⁻/corpus allatum; production increased to 1.52 ± 0.25 fmol hr⁻¹/corpus allatum when basal follicles were growing rapidly, and remained high during the period of oviposition. By 3 days following oviposition when females were brooding clutches, hormone production had declined to 0.46 ± 0.13 fmol hr⁻¹/corpus allatum. The addition of 60 μM farnesoic acid to the medium enhanced juvenile hormone biosynthesis at each stage examined. Lastly, elevating the level of l-methionine in the medium also enhanced hormone biosynthesis. Maximal hormone production was 32.8 ± 10.9 fmol hr⁻¹/corpus allatum, at an l-methionine concentration of 51 μM.     

Physiological approach to the onset of receptivity in female Acheta domesticus : I. Role of the corpora allata and ovaries

During the 32 hr following the imaginal moult, all female Acheta domesticus actively or passively refuse male courtship; they are unreceptive. As of 32 hr, the most precocious females become receptive and accept mating. At this time, juvenile hormone (JH III) synthesized by corpora allata (CA) is already detectable in hemolymph, while ecdysteroids (synthesized by ovaries) begin increasing at 48 hr. JH III and ecdysteroid levels in hemolymph were measured by RIA. After allatectomy and/or ovariectomy, all females became receptive, thus showing that CA and/or ovaries are not essential to the onset of receptivity. However, male courtship is longer for allatectomized females; in ovariectomized females, mating is delayed.     

Effects of precocene I and II on flight behaviour in Oncopeltus fasciatus, the migratory milkweed bug

Treatment of newly emerged adult Oncopeltus fasciatus with the corpus allatum inhibitors. 7-methoxy-2,2-dimethyl chromene or 6,7-dimethoxy-2,2-dimethyl chromene (preocene I and II) results in an inhibition of long-term flight (presumed migratory) behaviour in both males and females and inhibition of oögenesis in females. Treatment of reproductive females with precocene briefly stimulates flight behaviour (which ceases in such females as oviposition begins) and then subsequently inhibits it. Oviposition also ceases in such females and oöcyte resorption occurs. Topical application or injections of JH III to precocenetreated animals results in immediate restoration of the tendency to make long tethered flights while corpora cardiaca extract injections, corpora cardiaca implantation, sham implantation, sham injections and sham topical applications were ineffective in restoring prolonged flight behaviour to precocene-treated animals.Restoration of flight by JH III injection was observed within 1 hr after treatment with the hormone. These results indicate that JH is necessary for prolonged flight and presumably migratory behaviour in this species and its stimulatory effect on flight behaviour is immediate. Possible mechanisms of action of the hormone on flight behaviour are discussed.     

Social stimuli affect juvenile hormone during breeding in biparental burying beetles (Silphidae: Nicrophorus)

Extended biparental care is rare in insects but provides an excellent opportunity to investigate the interaction between the endocrine system and the physical and social environment in the regulation of this behavior. Burying beetles (Nicrophorus spp.) have facultative biparental care and depend on locating a small vertebrate carcass that they bury and prepare as food for their young. Commonly, both male and female Nicrophorus orbicollis remain in the burial chamber after eggs hatch to feed and guard the larvae. In both sexes, juvenile hormone (JH) rises rapidly in response to the discovery and assessment of the carcass; it returns to near baseline in 24 h; then in females it reaches very high titers at the onset of maternal care. In this paper, we investigate some social (presence of a mate, mating history, larval age) and environmental (carcass size) factors that may affect this endocrine profile. For females, neither the presence of a mate nor mating status (i.e., virginity) affected the initial rise of JH. However, the absence of a mate significantly depressed the JH rise in males. Eighty-seven percent of the single males buried the carcass like paired males but 87% also released pheromones to attract a mate. JH hemolymph titers in females whose broods were replaced every 24 h with newly hatch larvae were significantly higher than those of females rearing aging broods. Lastly, even though larger carcasses took longer to bury and prepare and oviposition was delayed, neither JH titers nor speed of ovarian development was affected by carcass size.     

Sex-role reversal in the tidewater goby, Eucyclogobius newberryi

Species in which females compete more intensely than males for access to mates are uncommon. Sex-role reversal in fishes has been documented only in species in which males bear eggs, such as pipefish and a mouth brooding cardinalfish. I investigated the reproductive behavior of the tidewater goby, Eucyclogobius newberryi (Gobiidae), to determine whether and to what degree this species is sex-role reversed. Males constructed and defended burrows for spawning in sand. Both sexes initiated courtship, but the female's breeding coloration was more striking. The intensity of sexual aggression was greater among females than among males. The female laid her entire clutch with a single male, and the male accepted only one clutch per brooding cycle. Both sexes spawned repeatedly (up to 12 times in aquaria), but fish did not form permanent pairs. Males cared for eggs in the burrow 9–11 days until hatching, and rarely if ever emerged to feed. Many aspects of male behavior (nest construction and defense, courtship, and parental care) were typical of most gobiids. On the other hand, female behavior (black nuptial coloration and intense female-female competition) was unusual, not only for gobiids but for animals in general. I therefore concluded that the tidewater goby is moderately sex-role reversed. Its sexual behavior is apparently unique among fishes because it is the only reported case of sex-role reversal in teleost males that do not bear eggs or developing young. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of clutch size on male egg-fanning behavior and hatching success in the goby, Eviota prasina (Klunzinger)

In fish that exhibit paternal care, the females often choose their mates on the basis of male traits that are indicative of the parental ability of the males. In a marine goby, Eviota prasina, males tend their eggs within their nests until hatching, and females prefer males that have longer dorsal fins and exhibit courtship behavior with a higher frequency as their mates. In order to clarify the relationship between these sexually selected traits and the parental ability of males of E. prasina, the factors affecting the hatching success of eggs within male nests and the male parental care behavior were examined in an aquarium experiment. Females spawned their eggs in male nests and the clutch size of females showed a high individual variation (range = 88-833 eggs). The hatching success of eggs within male nests showed a positive correlation with the time spent by males in fanning eggs and the clutch size. In contrast to the prediction, however, the hatching success did not show a significant correlation with the sexually selected traits, i.e., the male dorsal fin length and the frequency of courtship displays. Moreover, multiple regression analysis indicated that the time spent by the males in fanning was the most important factor affecting the survival rate of the eggs. The time spent by males in fanning behavior was influenced by the clutch size within their nests; the fanning behavior of males occurred with a higher frequency when they tended larger clutches. Males are required to invest a greater effort in egg-tending behavior to achieve a higher hatching success when they receive larger clutches, probably due to the greater reward for their parental behavior. Based on their mate choice, females may obtain other benefits such as high quality offspring.     

The effect of ovariectomy on reproductive behaviour and physiology of adult female ring-legged earwigs, Euborellia annulipes

The effect of ovariectomy on feeding, mating, Juvenile Hormone (JH) production, and maternal behaviour was assessed in female ring-legged earwigs, Euborellia annulipes (Lucas) (Dermaptera: Carcinophoridae), during the first 16 days of adult life (the first gonadotrophic cycle and early brooding). Ovariectomy of 2-day-old adults did not affect weight gain, nor did it alter mating behaviour on day 7. Similarly, ovariectomy did not prevent the increase in JH biosynthesis that accompanies vitellogenesis in this species, which suggests a cycle of JH production that is not dependent on the presence of the ovaries. Both ovariectomy and mating status affected feeding behaviour. Most introduced eggs were consumed (i.e. disappeared) within 24 h, and younger (7-day-old) females consumed more eggs than did older ones. However, 12-day-old intact virgins and 16-day-old ovariectomized, mated females consumed fewest eggs, and allowed some hatching. Thus, ovariectomy did not abolish changes in feeding behaviour that normally accompany reproduction but, instead, appeared to delay the reduction in feeding that normally accompanies the completion of the cycle of egg development. By contrast, mating enhanced the reduction in feeding late in the reproductive cycle. Mating significantly enhanced maternal behaviour in both ovariectomized and sham-operated females. Hatching success from egg clutches introduced to day 16 virgin or mated females that had been ovariectomized or sham-operated on day 2, was significantly greater in the mated groups.     

Time-course haemolymph juvenile hormone titres in solitarious and gregarious adults of Schistocerca gregaria, and their relation to pheromone emission, CA volumetric changes and oocyte growth

The haemolymph JH III titres in solitarious and gregarious adult desert locusts, Schistocerca gregaria, were examined in relation to corpus allatum (CA) volumes, aggregation-maturation pheromone production in males and oocyte growth in females. The JH titres of gregarious females were generally higher than those of solitarious females at all ages studied. The titre patterns, however, were similar: relatively high on day 10, dropping to low levels between days 20 and 25, before rising again by day 25. In the solitarious males, the JH titre was very low on day 10 after fledging, but increased gradually and reached a maximal amount on day 30. The JH titre in gregarious males was low on day 10, elevated on day 15 coinciding with the start of the production of the pheromone, and dropped to a relatively low level on day 20 around the time of maximal pheromone production, then rising again by day 25. These results suggest that biosynthesis of the pheromone is associated with a high JH titre peak in the haemolymph. Although a clear relationship was found during the first gonadotropic cycle between JH titres, on one hand, and CA volume and oocyte growth, on the other, in both phases, no such correlation could be discerned in the second cycle.     

Juvenile Hormone Is Required in Adult Males for Drosophila Courtship

Juvenile Hormone (JH) has a prominent role in the regulation of insect development. Much less is known about its roles in adults, although functions in reproductive maturation have been described. In adult females, JH has been shown to regulate egg maturation and mating. To examine a role for JH in male reproductive behavior we created males with reduced levels of Juvenile Hormone Acid O-Methyl Transferase (JHAMT) and tested them for courtship. JHAMT regulates the last step of JH biosynthesis in the Corpora Allata (CA), the organ of JH synthesis. Males with reduced levels of JHAMT showed a reduction in courtship that could be rescued by application of Methoprene, a JH analog, shortly before the courtship assays were performed. In agreement with this, reducing JHAMT conditionally in mature flies led to courtship defects that were rescuable by Methoprene. The same result was also observed when the CA were conditionally ablated by the expression of a cellular toxin. Our findings demonstrate that JH plays an important physiological role in the regulation of male mating behavior.     

Hormonal controls on reproduction in female heteroptera

A survey of the literature related to hormonal control of reproduction in female heteropterans reveals many common features. Juvenile hormone secreted by the corpus allatum is the principal hormone governing vitellogenesis. Feeding and nutrition affects egg development via juvenile hormone secreted by the corpus allatum, which is under inhibitory control from the brain. Information about feeding reaches the brain via a humoral route. Similarly, mating increases egg production by altering the degree of inhibition of the corpus allatum by the brain, although the nature of the mating stimulus and the route by which the stimulus reaches the brain remains uncertain. There may be one or more stimulatory factors acting on the corpus allatum. Progress in identifying controls on the corpus allatum is hindered by our ignorance of the identity of the juvenile hormone(s) acting in Heteroptera. Ovulation and oviposition are under the control of a myo-active peptide from the brain, and its release is governed by hormonal inputs from both mating and the ovary. The ovarian input appears to consist of ecdysteroid. A role for ovarian ecdysteroid in controlling the corpus allatum remains uncertain. Arch. Insect Biochem. Physiol. 35:443–453, 1997. © 1997 Wiley-Liss, Inc.     

Phase polymorphism in Schistocerca gregaria: Assessment of juvenile hormone synthesis in relation to vitellogenesis

Juvenile hormone (JH) synthesis by the corpora allata of gregarious and solitarious phase females of Schistocerca gregaria was determined in vitro during the penultimate and last stadia as well as during the first gonotrophic period of adults. Generally, the corpora allata of solitarious females showed higher rates of JH synthetic activity. In addition, in adult females there was a temporal difference between the corpora allata activities of gregarious and solitarious locusts, the latter exhibiting relatively higher rates of JH synthesis early in the first gonotrophic period. The corpus allatum volumes of solitarious females were also generally larger than those of their gregarious counterparts; there was no synchrony between fluctuations in JH synthetic activity and changes in corpus allatum volume in either phase.The early onset of relatively high JH synthetic rates in solitarious females was correlated with the early detection, by rocket immunoelectrophoresis, of vitellogenin in the haemolymph and vitellin in the oöcytes. Vitellogenin appeared in the haemolymph on day 4 in solitarious females and on day 6 in gregarious females and vitellin appeared in the oöcytes on days 6 and 8 respectively. Oöcyte length at which vitellogenesis was first detected was 1.8 mm for gregarious and 1.3 mm for solitarious females. However, despite the accelerated onset of both vitellogenin synthesis and uptake, oöcyte maturation time of solitarious females was longer. In both gregarious and solitarious females, vitellogenin titres increased until oöcytes reached a length of about 4 mm and declined thereafter. Vitellin content of ovaries increased proportionately to oöcyte growth until they attained a length of 5.0 mm. The subsequent increase in length of oöcytes to maturity is attributed to postvitellogenic growth, possibly by hydration.     

浅斑近微蛛体形大小对交配行为的影响

理论和实验表明体形大小是许多动物择偶的重要信号。体形大小与产卵大小、最终产卵数量、后代适合度等都有着密切的关系,因此动物利用体形大小为信号来择偶可以获得高的生殖利益。目前研究交配行为和体形大小的关系的文献较少,特别在微蛛亚科。本文以浅斑近微蛛为实验材料,在室内研究了体形大小对交配行为的影响。测量了体重,体长,头胸甲与腹部的长和宽,以头胸甲的面积(头胸甲的长与宽的乘积)为变量来表示体形大小。以雄蛛的行为为依据,将其交配行为划分为4个时期:潜伏期、求偶期、插入期和纳精期,并记录了各个时期的持续时间。通过分析,发现了一种微蛛新的交配模式,即可将浅斑近微蛛的插入期分为三个阶段:首先是大约25min长插入期,接着是一个大约15min的中度插入期,最后是一个大约5min的短插入期。结果表明,在本试验条件下,浅斑近微蛛的体形大小对其交配行为的潜伏期、求偶期、插入期和纳精期的持续时间都没有影响,对插入期的3个阶段的长短也没有影响。     

红瘰疣螈的繁殖生态

红瘰疣螈(Tylototriton shanjing)为国家Ⅱ级重点保护野生动物,对其繁殖生态尚无系统的研究。2007～2010年在云南省新平县哀牢山对红瘰疣螈形态、繁殖栖息地、求偶和交配行为、产卵及孵化等繁殖特征进行了研究。结果表明,红瘰疣螈雌雄两性在广泛的形态学度量特征上存在着差异;繁殖栖息地主要为稻田和潮湿的沟渠;参与繁殖的雌雄成体性比随繁殖时间的推移而不断变化,繁殖前期和后期雄性比例高,中期雌性比例高。求偶和交配主要在陆地潮湿的水沟中完成,也可在静水中进行。成体产卵活动从5月初持续至6月下旬,呈现出波浪式的产卵进程,个体完成产卵平均时间为(22.2±2.7)h。繁殖前期雌螈产卵于稻田,中后期产于多杂草的田埂草丛和泥壁,平均产卵数(126±18)枚(n=17)。平均孵化期(17.3±0.1)d(n=225),孵化率59.8%(n=79),孵化时幼体平均体长12.7mm(n=6)。     

Oosorption in the stink bug Plautia stali: role of Juvenile hormone in the induction of oosorption

To clarify the role of Juvenile hormone (JH) in the induction of oosorption in females of the stink bug Plautia stali Scott (Heteroptera: Pentatomidae), the effects of extirpation and implantation of the corpus cardiac‐corpus allatum complex (CC‐CA) are examined in fed and starved adults, respectively. Removal of CC‐CA induces oosorption in fed females, whereas CC‐CA implantation stimulates ovary development in starved females. Transection of the nervous connections between the brain and CC‐CA also exerts a stimulatory effect on ovary development. Uptake of yolk protein by the oocytes, assessed in terms of incorporation of a fluorescence dye, occurs on the day after food deprivation but ceases within 1 day after allatectomy. When females are deprived of food, beginning on day 3 of adult life, and treated with JH III skipped bisepoxide (JHSB₃) on the same day, their ovaries develop in a dose‐dependent fashion. Approximately half of the starved females that received JHSB₃ application on day 5 undergo oosorption in the terminal oocytes. This indicates that the critical starvation period for oosorption induction is approximately 2 days, and the earlier half of this period may reflect the time required for the brain to detect poor nutritional condition. During the latter half, in response to food deprivation, the brain inhibits JH biosynthesis by the corpus allatum through nervous connections, resulting in a low JH titre, which in turn induces oosorption.