ACTIVATION OF THE CORPORA ALLATA IN RELATION TO OVARIAN MATURATION IN THE SEASONAL FORMS OF THE BUTTERFLY, POLYGONIA C-AUREUM L.

In Polygonia c-aureum , there are two seasonal forms, viz. , the summer form and the autumn form. Previous experiments (E ndo , 1970) showed that the corpora allata of the summer form accelerate the maturation of ovarian follicles soon after imaginal ecdysis. On the other hand, the corpora allata of the autumn form do not stimulate ovarian maturation during a period of 2 to 3 weeks after the emergence.
In the summer form (S) as well as in the autumn form (A), the corpora allata remained in an inactive state for about 15 days after emergence when they had been isolated microsurgically from the brain and the corpora cardiaca during the larval period. Further, when separation of the brain into the right and left hemispheres or ablation of the medial neurosecretory group cells of the pars intercerebralis had been carried out on S-pupae of 28 hr after pupation or of earlier ages, they developed into autumn form in respect to wing pattern and their corpora allata did not stimulate ovarian maturation until 2 to 3 weeks after emergence. On the other hand, when the above operations had been performed 34 hr after the pupation or of later ages, they developed into summer form in respect to wing pattern and ovarian maturation was evident soon after the emergence. In these cases, stimulation of the corpora allata is closely connected with the development of seasonal-forms of wing pattern.
From these experiments, it is clear that the medial neurosecretory group cells of the pars intercerebralis in S-insects stimulate the corpora allata about 30 hr after pupation by way of the nervi corporis cardiaci and the activated corpora allata promote ovarian maturation throughout adult life. In A-insects, on the other hand, the medial neurosecretory group cells of the brain are inactive and fail to activate the corpora allata which in turn have no influence on ovarian maturation.     

Mating and diapause in hibernating adults ofMenida scotti puton (Heteroptera: Pentatomidae)

InMenida scotti aduts which mate during hibernation, we examined the effect of photoperiod on diapause induction in terms of the developmental degree of reproductive organs and corpora allata. In a hibernating population, mating season and physiological changes related to dipause were investigated. When newly emerged adults were reared under long- or short-day conditions, reservoir of the ectodermal accessory gland and corpora allata in males developed, while the developments of ovary and corpora allata in females were suppressed under both conditions. This suggests that diapause of this species is induced only in females independently photoperiodic conditions during adult stage. In a hibernating population, mating was observed from early to late November and from late March to early May. Observations of the development of reproductive organs and corpora allata suggest that diapause is induced only in females in the former period, while both sexes are not in diapause in the latter period.     

Flight ability and reproductive development in newly‐emerged pine weevil Hylobius abietis and the potential effects of climate change

• 1 Adult pine weevils Hylobius abietis emerge from conifer root‐stumps, on which larvae develop, over an extended period during summer and autumn. Newly‐emerged weevils were tested for their ability to fly and assessed for wing muscle and reproductive development. In addition, the effect of summer–autumn maturation feeding on reproductive development was assessed in field bioassays.
• 2 There was considerable variation in development between newly‐emerged weevils that was related to the timing of emergence. The first weevils, emerging in early July, weighed less than later‐emerging ones, had undeveloped flight muscles and did not fly. Over the emergence period, wing muscle size and flight ability increased markedly, with 50–60% flying by mid‐September. Differences between emerging adults are likely to have been affected by temporal changes in the quality of the bark on which the larvae feed.
• 3 Reproductive development lagged behind that of wing muscles but, in early August, there was a rapid increase in the proportion of weevils with immature eggs and a corresponding increase in oocyte size. However, although wing muscles were fully formed in later‐emerging weevils, immature eggs were only approximately 10% of the volume of mature eggs.
• 4 In field bioassays of summer–autumn maturation feeding, eggs continued to develop and some weevils laid mature eggs. Feeding and development during the pre‐overwinter period is likely to influence winter survival and also dispersal and reproduction in the following spring.
• 5 The potential effects of climate change on the weevil life cycle are briefly discussed. Weevils are likely to benefit from the higher temperatures and later autumns predicted under climate change, resulting in an increase in damage to transplants.

     

Demographic study of the reproductive potential of pear psylla, Cacopsylla pyri

Longevity and fecundity of pear psylla adults, Cacopsylla pyri (L.) (Homoptera: Psyllidae), were studied in Greece under field conditions, during 1991/92 and 1992/93. Net fecundity (mean fecundity of cohort) of the overwintered females (winter form) was low (24.1 and 43.4 eggs per female for 1991/92 and 1992/93 respectively) because only a small fraction of the females survive reproductive diapause. Surviving females, however, are capable of producing a relatively high number of eggs (135.0 and 151 9 eggs per female for the two seasons respectively). Net fecundity of summer form females was very high in spring (343.2 and 406.8 eggs per female for 1992 and 1993 respectively), relatively high in early autumn (130.4 and 192.5 eggs per female) and very low in summer (21.9 and 46.5 eggs per female). Male longevity was in all cases shorter than that of female. Longevity of both sexes of the summer form was higher in spring and autumn (for females it ranged from 22.3 to 28.4 days) than it was in summer (for females it ranged from 14.3 to 17.4 days).     

Regulation of reproductive behaviour and egg maturation in the tobacco hawk moth, Manduca sexta

ABSTRACT. The virgin female tobacco hawk moth, Manduca sexta, flies during the early scotophase in an LD 16:8 cycle at 24C then begins 'calling' within 2h. Mating lasts 3–4 h. Oviposition occurs in the succeeding scotophases if a tobacco plant is present. The switch from virgin 'calling' behaviour to mated ovipositional behaviour is mediated by the presence of sperm and/or associated testicular fluids in the bursa copulatrix. The corpora allata, which are necessary for egg maturation in this species, are activated via the NCC I and II around the time of eclosion. Feeding increases the activity of the corpora allata in the virgin female (as judged by the number of eggs matured in 4 days) but mating brings about a further stimulation of the activity of the corpora allata. The stretching of the bursa copulatrix by the insertion of the spermatophore during mating is probably the trigger for this response. Continued neural input from the bursa copulatrix to the brain is necessary to maintain the increased activity of the corpora allata.     

The phenology of Onitis alexis (Coleoptera: Scarabaeidae) in the Araluen Valley: Survival in a marginal environment

The introduced African dung beetle, Onitis alexis Klug, has become established in the warmer regions of Australia. The south-eastern limit of its current distribution is Moruya, NSW, and the Araluen Valley 50 km inland. At Araluen newly emerged beetles are present in dung in late spring, summer and autumn. Egg-laying starts 1-2 weeks after emergence and continues throughout the summer and autumn, as indicated by the presence of parous females in the population and of broods under experimental pads. Eggs laid in December/January produce adults in late summer and autumn, those laid from February to April produce adults in the following spring and summer. In the laboratory, mortality of larvae is high in cold (0–16°C), wet conditions and their development is delayed in warm (25°C and 27°C), dry conditions. This delay was confirmed in the field during the summer drought of 1982-83 when predicted times of emergence (based on day-degree summation in the soil) always preceded the observed emergence time of the local population, as well as preceding the emergence of beetles developing from eggs laid at known times. Follicle resorption in adult females was related directly to increasing age and to rainfall. Dung collected from hayed-off pasture did not affect fecundity, but caused larval mortality. Adults survived the winters at Araluen in some years, and immatures survived best during dry winters, being facilitated in this by a cold-induced larval diapause. Onitis alexis larvae can survive wet or dry summers, and cold dry winters (down to about 0°C) but not wet winters. This seems to be the major factor limiting the southern distribution of the species.     

Système endocrine et physiologie de la diapause imaginale chez le criquet égyptien, Anacridium aegyptium

The Egyptian locust, Anacridium aegyptium, has four protocerebral neurosecretory centres: the A to B neurosecretory cells of the pars intercerebralis (the A cells are rich in fuchsinophil material and the B cells are devoid of fuchsinophil neurosecretion), the voluminous C neurosecretory cells poor in neurosecretion, and the median sub-ocellar neurosecretory cells.From September to the beginning of January, imaginal diapause is characterized by an accumulation of the median neurosecretion in the pars intercerebralis-corpora cardiaca system, by small corpora allata, and, in the female, by a stop in oöcyte development although the male's sexual activity is still not altered. Allatectomy suppresses neither the male's sexual behaviour nor its fecundity. From January, the increase of the photoperiod causes a release of the median neurosecretion in both sexes, an increase of the volume of the corpora allata, and breaks ovarian diapause.In autumn, the implantation of the male's or female's corpora allata of Anacridium does not stimulate ovarian growth of diapausing females. On the contrary, the implantation of corpora allata or of pars intercerebralis or of corpora cardiaca of Locusta migratoria migratorioides (locust without diapause) causes ovarian development of the diapausing females of Anacridium. Thus, in the two sexes of the Egyptian locust, the corpora allata are inactive during the female ovarian diapause. The imaginal diapause of Anacridium affects both sexes (stocking of median neurosecretion, arrest of the corpora allata). If diapause does not seem to affect the male's development, it is because its sexual activity is free from the pars intercerebralis and corpora allata.The corpora allata of Anacridium show a sexual dimorphism in the active adult: they are smaller in the male and have more mitosis in the female. An explanation of this dimorphism is advanced.     

A STUDY OF THE BIOLOGY AND CONTROL OF ANISOPUS FENESTRALIS (SCOPOLI, 1763), A FLY ASSOCIATED WITH SEWAGE FILTERS

In work on the control of the sewage fly Anisopus fenestralis (Scopoli, 1763), it was shown that the larval phase was considerably lengthened by limiting the food supplied. The effects of food supply and temperature are considered in relation to the incidence of the adult fly in the filters. The assessment of the fly population of sewage filters by tray traps, as previously used by other workers, was investigated. Both light and temperature were found to affect the number of A. fenestralis entering the trays: it is concluded that although the trays do not accurately assess the A. fenestralis population of a bed, nor measure the rate of emergence from the bed, they are of value in assessing the relative effect of different control measures. In the filters the period of maximum abundance was during the spring, followed by a period of reduced numbers throughout the summer, with a recovery in the autumn giving relatively high numbers throughout the winter. Emergence of A. fenestralis from the filters is influenced by climatic factors, especially temperature and light; a diurnal variation in the rate of emergence was also observed. Because of this effect of temperature on emergence, the flies were only present above the filters in the warmer periods of the year; and because of the reduced numbers in the filters in the summer, the flies were only abundant above the beds during the spring and early summer and in the autumn. BHC applied as a water-dispersible powder was more effective than in the form of an emulsion. It was also most effective when used against the larval phase.     

Humoral inhibition of the corpora allata in larvae of Diploptera punctata: Role of the brain and ecdysteroids

Juvenile hormone synthesis by adult female corpora allata was inhibited following implantation into final-larval-instar males; inhibition was prevented by decapitation of the larval hosts on day 11 (prior to the head critical period for moulting), but not by decapitation on day 13. Implantation of one larval protocerebrum restored inhibition of implanted corpora allata, demonstrating that the brain releases an inhibitory factor. Corpora allata implanted into larvae decapitated on day 11 were inhibited by injections of 20-hydroxyecdysone. Since treatment of corpora allata with 20-hydroxyecdysone in vitro did not inhibit juvenile hormone synthesis, ecdysteroids probably act indirectly on the corpora allata. Juvenile hormone synthesis and haemolymph ecdysteroid concentration were measured following implantation of corpora allata along with two larval brains into larval hosts. Brain implantation did not affect ecdysteroid concentration, but did inhibit juvenile hormone synthesis, even in animals with low haemolymph ecdysteroid concentration. Incubation with farnesoic acid stimulated juvenile hormone synthesis by corpora allata from males early in the final larval stadium, but not after day 8, showing that one of the final two reactions of juvenile hormone synthesis is rate-limiting in larval corpora allata at this stage. Adult female corpora allata which had been humorally inhibited by implantation into larvae were stimulated by farnesoic acid.     

Autogeny and endocrine involvement in the reproduction of tropical flesh flies (Diptera: Sarcophagidae)

Autogeny is highly developed among the Sarcophagidae in tropical Africa. Unlike their temperate region relatives, the tropical species examined can mature the first batch of eggs without an adult protein meal, and they do so without the long period of delay usually seen in autogenous species. Protein deprivation, however, does reduce the number of eggs matured by about one-third. The tropical and temperate flies appear to share a common endocrine mechanism controlling egg maturation. Removal of the medial neurosecretory cells of the pars intercerebralis prevents egg maturation. Reimplantation of clusters of MNC restores the ability to mature eggs. Extirpation of the corpora allata reduces the percentage of females that mature eggs to about 70%, and the females that do mature eggs produce fewer eggs. The significant difference between the tropical and temperate species centers on the trigger that sets the neuroendocrine system into action. For the tropical species, the brain is activated immediately and does not require the trigger of a protein meal.     

Population dynamics of the cattle tick Rhipicephalus (Boophilus) microplus in a subtropical subhumid region of Argentina for use in the design of control strategies

The population dynamics of Rhipicephalus microplus (Ixodida: Ixodidae) in northwest Argentina was analysed to support the design of strategic methods for its control. Both parasitic and non‐parasitic phases were studied. The seasonal activity of R. microplus in its parasitic phase was characterized by three peaks in abundance: the first in mid–late spring; the second in summer, and the third in autumn. The non‐parasitic phase of R. microplus was characterized by a long total non‐parasitic period observed after exposures of females from mid‐summer to early autumn, a short total non‐parasitic period observed after exposures of females from late winter to late spring, a short period of larval longevity in early and mid‐summer, and no hatch of the eggs produced by females exposed in mid‐ and late autumn and winter. Treatments of cattle administered during the period from late winter to late spring will act on small cohorts of R. microplus, preventing the emergence of larger generations in summer and autumn. A 17‐week spelling period starting in late spring and early summer will be necessary to achieve optimal control of R. microplus free‐living larvae. If spelling begins in mid‐ or late summer or in autumn, the required period will be 26–27 weeks.     

Quantitative studies on the activity of the corpora allata in adult male Locusta and Schistocerca

Juvenile hormone has been detected in the haemolymph and corpora allata of adult male Locusta and the haemolymph of adult male Schistocera by a modified Galleria bioassay. The hormone was readily detected in the haemolymph of insects immediately after the final ecdysis, but then became difficult to detect until 2 days prior to the onset of sexual maturation. In sexually mature insects the titre of juvenile hormone was maintained at a constant level. The corpora allata of adult male Locusta increased in size throughout adult life. The juvenile hormone content of the corpora allata was low during the period of somatic growth, but increased at the onset of sexual maturation. Sectioning of the nervi corporis allati I in insects immediately after the final ecdysis prevented the normal increase in size of the corpora allata, but did not render them inactive since juvenile hormone was detected in the haemolymph after the operation. The half life of juvenile hormone in the haemolymph of allatectomized adult male Locusta was 1 to 2 hr.     

The management of metabolic energy storage during the life cycle of mayflies: a comparative field investigation of the collector-gatherer <Emphasis Type="Italic">Ephemera danica</Emphasis> and the scraper <Emphasis Type="Italic">Rhithrogena semicolorata</Emphasis>

The concentration and seasonal dynamics of the major energy storage components, triglycerides and glycogen, were measured in two species of mayfly (Rhithrogena semicolorata and Ephemera danica) with contrasting life cycle strategies living in a small mountain stream. E. danica is a burrowing, semivoltine collector-gatherer; R. semicolorata is univoltine and scrapes periphyton from stones. This is the first publication which focuses on the role of metabolic energy sources during the larval life span of two mayfly species until the larvae emerge. Although triglycerides are the major energy reserve in both species (>84% of total energy storage) throughout the whole larval development their seasonal dynamic differed considerably. In R. semicolorata the triglyceride concentration declined during the last weeks prior to emergence in both sexes. The same pattern was found in female larvae of E. danica, but not in male E. danica. It is suggested that females use triglycerides in the last larval stages for egg maturation, which is completed in the last larval instar. In male E. danica the triglyceride concentrations remained high until emergence, presumably due to their high energy demands as adults for their swarming flights. Glycogen concentrations did not show such a difference between species and sexes. Its significance as a storage substrate for energy is rather low; however, concentrations decreased in both species and sexes prior to emergence.     

Life cycle of an endangered riffle beetle,Leptelmis gracilis Sharp (Coleoptera: Elmidae), in the Hiikawa River system,Shimane prefecture,Japan

We studied the life cycle of the riffle beetle Leptelmis gracilis Sharp, 1888 from a population located in a river stream with lotic environments. Samples were collected monthly, between September 2018 and August 2019, from a tributary of the Hiikawa River in Izumo city, Shimane Prefecture, Honshu, Japan. Larvae were separated into five distinct groups based on size. The first and last instar larval sizes were identified through rearing methods. From these results, we determined that the larval stage of this species consists of five instars. From the monthly evaluations, the number of individuals corresponding to each instar period suggested that last-instar larvae were dominant in May and that new adults emerged from July to August. Landing and pupation were estimated to occur from May to June. Monthly observations revealed that mature eggs were present in the female abdomen from April to June, as well as from August to September. It is, therefore, predicted that overwintering adults mainly oviposit from spring to early summer, while new adults oviposit from late summer to early autumn.     

Effects of decapitation and ovariectomy on the regulation of juvenile hormone synthesis in the cockroach, Diploptera punctata

Corpora allata from Diploptera punctata females at adult ecdysis or at the end of the last-larval stadium, when implanted into decapitated females, underwent a cycle of juvenile hormone synthesis similar in timing and magnitude to that of glands implanted into control animals which had been starved and allatectomized. Starvation did not alter the cycle in rates of juvenile hormone synthesis of sham-operated animals.Decapitation of ovariectomized animals resulted in no cycle in rates of juvenile hormone synthesis by implanted adult corpora allata; however, implantation of an ovary along with the corpora allata into decapitated, ovariectomized hosts resulted in a cycle of juvenile hormone synthesis. In control animals, which retained their heads but were starved and allatectomized as well as ovariectomized, the implanted corpora allata showed a cycle of juvenile hormone synthesis only when implanted with an ovary. The maximal rates of juvenile hormone synthesis by the corpora allata in both experimental and control conditions were lower than normal, likely due to the repeated trauma of surgery. However, at no time from eclosion to the end of the first gonotrophic period was the brain necessary for the cyclic response of the corpora allata to the presence of the ovary.     

Control of reproduction in female cockroaches with special reference to Nauphoeta cinerea—I. First pre-oviposition period

Prior to the first oviposition, a receptivity centre, perhaps neurosecretory cells in the brain, controls the female's acceptance of courting males. In L. maderae this centre is affected by starvation. A brief exposure to food can induce mating but is inadequate for oöcyte development. Before the first ovulation starvation has no effect on receptivity in N. cinerea.

In N. cinerea mechanical stimulation caused by the firm insertion of the spermatophore in the bursa copulatrix releases stimuli via the nerve cord to the brain which render the female unreceptive and, at the same time, increases the activity of the corpora allata resulting in rapid development of the oöcytes.

The mechanical presence of the oötheca in the uterus also has two principal effects. Like spermatophore insertion, it inhibits mating. But its effect on the corpora allata is inhibitory, rather than stimulatory, and, consequently, the oöcytes remain underveloped for almost the entire gestation period. The effectiveness of inhibitory stimulation from the stretched uterus depends upon the period in the reproductive cycle in which it occurs-i.e. on the physiological state of the female. In N. cinerea uterine stretching inhibits mating and oöcyte development after oviposition or during gestation but is not effective when exerted during the first pre-oviposition period. In P. surinamensis, uterine stretching does not inhibit the corpora allata prior to the first ovulation but does prevent oöcyte development during gestation.

In fed L. maderae and N. cinerea there appears to be a synergistic action of nutrition and mating in controlling the rate of oöcyte development. Mating (mechanical) and feeding (chemical) stimuli are both usually required for activating the corpora allata to their fullest extent so that the oöcytes mature at their maximum rate. There is some indication that mating stimuli in N. cinerea and L. maderae are effective in further stimulating the corpora allata only if the corpora allata have reached a certain level of activity, if activating stimuli have begun to occur in the brain, or if the mating stimulus occurs in combination with nutritional factors. Thus, the corpora allata in starved virgin females of N. cinerea become sufficiently active so that some yolk is deposited in the oöcytes but these oöcytes do not mature; mating is effective in further stimulating the endocrine glands in these starved females and oviposition occurs in about the normal period. In starved virgins of L. maderae the corpora allata are virtually inactive and yolk is not deposited in the oöcytes; mating has no effect on oöcyte development in starved females. D. punctata differs from both the above species in that the corpora allata in the virgin female usually remain inactive whether she feeds or starves. Mating stimuli alone can activate the corpora allata, in fed or starved females, and consequently the oöcytes mature.     

Effects of ovariectomy and mating on the activity of the corpora allata in adult female Blattella germanica (L.) (Dictyoptera: Blattellidae)

In adult female cockroaches, the ovary greatly affects the synthesis of Juvenile Hormone (JH) by the corpora allata, and in females of some cockroach species, removal of the ovaries results in a permanent depression of JH synthesis. We report that the corpora allata in ovariectomised, adult virgins of the German cockroach, Blattella germanica (L.), increase and then decrease in activity, as they do in intact females. Moreover, the distal tubules in the left colleterial glands of ovariectomised females accumulate abundant protein, the production of which is regulated by JH. In both ovariectomised and sham‐operated females, the activity of the corpora allata more than tripled between days 1 and 4 of adulthood, during which the oöcytes of sham‐operated females grew considerably in length. The corpora allata of sham‐operated females produced even more JH on day 7, but very little on day 10, by which time all females had oviposited. The glands of ovariectomised females, by constrast, produced a similar amount of JH on day 7 as on day 4, but much less on day 10. Beginning on day 13, the activity of the corpora allata increased again in ovariectomised females, an increase that did not occur until day 22 in sham‐operated females. Mating of ovariectomised females on day 6 resulted in a significant increase in the activity of the corpora allata by day 10. We conclude that both the ovary and mating stimulate the synthesis of JH early in the reproductive cycle, but that neither is needed for the occurrence of a complete cycle of JH synthesis.     

Antibiosis component of resistance in sorghum to sorghum midge, Contarinia sorghicola

Sorghum midge, Contarinia sorghicola Coq. (Diptera: Cecidomyiidae) is an important pest of grain sorghum, and host-plant resistance is one of the most effective means of controlling this pest. We studied the antibiosis mechanism of resistance in sorghum to C. sorghicola in a diverse array of midge-resistant and midge-susceptible genotypes. Data were recorded on adult emergence, postembryonic developmental period, number of mature eggs in the ovary, fecundity, larval survival from artificially implanted eggs; and the tannins, soluble sugars, and protein content of 10-day old and mature grains during the 1982-91 rainy and post-rainy seasons. Adult emergence was significantly lower in the midge-resistant genotypes compared with the susceptible controls. Initiation of adult emergence was delayed by 4–8 days on DJ 6514, IS 8571, IS 9807, IS 10712, IS 19474, IS 19512, ICSV 830 and ICSV 197. Postembryonic developmental period was prolonged on DJ 6514, IS 15107, IS 3461, IS 7005, IS 19474, ICSV 831 and ICSV 197. However, the delay in adult emergence or the extended developmental period was not observed during the post-rainy season in some genotypes. These differences in the expression of antibiosis to midge in resistant genotypes over seasons may be attributed to the effect of environmental conditions on the insect development and chemical composition of sorghum grain. Amounts of tannins and proteins were generally greater in the midge-resistant lines compared with the susceptible ones (except tannins in DJ 6514) while the soluble sugars were low in the midge-resistant lines (except TAM 2566). These differences in chemical composition of the grain between genotypes and variations over seasons have been discussed in relation to the expression of antibiosis mechanism of resistance to the sorghum midge. Antibiosis to sorghum midge was also evident in terms of smaller size of larvae, lower number of eggs in the ovary, reduced fecundity, and larval survival. Midge-resistant lines have diverse effects on the biology of this insect. Antibiosis along with other components of resistance can be used to develop cultivars with stable resistance to C. sorghicola.     

ENDOCRINOLOGICAL STUDIES ON SPERMATOGENESIS IN THE SILKWORM, BOMBYX MORI L.

When embryonic testes 1 or 2 days before hatching were transplanted into 5 kinds of hosts (5th instar larvae, “fresh” pupae just after pupation, isolated pupal abdomens and 3-day-old pupae with and without their original corpora allata), the testes transplanted into 5th instar larvae grew most conspicuously and spermiogenesis began in many cysts. A few spermatidal cysts were observed in the testes transplanted into fresh pupae. No signs of maturation were observed in the testes transplanted into other hosts. It is concluded that prothoracic gland hormone might be responsible for the precocious maturation of young testes. On the other hand, the initiation of spermiogenesis was delayed, in comparing with controls, in the 3rd instar larval testes as follows: the testes transplanted into 3-day-old pupae, the testes transplanted into isolated pupal abdomens together with adult corpora allata and the testis into which corpus allatum of a 3rd instar larva was inserted. It is concluded that corpora allata hormone exerts an inhibitory effect on spermatogenesis.