Juvenile hormone in larval diapause of the codling moth,Laspeyresia pomonella L. (Lepidopterae,Tortricidae)

Summary Whereas in last instar larvae ofL. pomonella kept under long-day-conditions (LD), the JH-titer is temporarily reduced to zero, it stays relatively high in short-day-conditioned (SD) larvae which enter diapause. Application of JH or a juvenoid to LD-larvae results in diapause, if the treated insects are kept under SD-conditions. From these results it is concluded that inL. pomonella diapause is initiated by a relatively high titer of JH during the last larval instar.     

Photoperiodic summation is temperature-dependent inPyrrhocoris apterus (L.) (Heteroptera)

Summary InPyrrhocoris apterus, a low temperature, 15°C, prevented the termination of diapause by long days and, unexpectedly, also the induction of diapause by short days. Both responses were enabled at a higher temperature, 26°C. In contrast to current concepts, it was proved that the summation of photoperiodic signals was temperature-dependent, since the morphogenetic development was prevented by starvation.     

Existe-t'il une action particulière des différentes longueurs d'onde du spectre visible sur la physiologie des chrysalides et prénymphes dePieris brassicae conditionnées à la diapause?

Summary Pieris brassicae larvae were reared under 9 h/24 h white light and 20°C (conditions determining the diapause status). From the pupal moult they were exposed for 20 days under different wavelengths (absorbed or not by the green integumentary pigment: pterobilin). This treatment has no effect on diapause.     

Effects of diapause and host species on some morphometric characters inTrichogramma (Hym.: Trichogrammatidae)

Adult morphology ofTrichogramma is modified by environmental conditions during the preimaginal development. For instance, the low temperatures inducing diapause cause a decrease of the ratio length of longest seta on male flagellum/width of flagellum inT. evanescens. The species of the host also influences numerous body ratios. So, in females, the development of tibiae with regard to wings is more important withScotia ipsilon than withGalleria mellonella. These results confirm the necessity of performing comparative morphological studies on individuals reared in the same conditions.     

Threshold and quantitative photoperiodic responses exist in an insect

The photoperiodic response for the induction of adult diapause and that for the determination of nymphal body coloration were compared inPlautia stali Scott (Heteroptera: Pentatomidae). The former was an all-or-none response with a distinct threshold, but the latter was a graded response which varied quantitatively with the photophase duration. The photoperiodic clock in this species is discussed.     

Embryonic diapause in annual fishes: Evaporative water loss and survival

Summary The effects of partial desiccation on the survival of diapause I, diapause II, and pre-hatching embryos of the annual fishN. guentheri were investigated. Embryos at diapause II were found to be the most resistant stage. Prolonged exposure of diapause II embryos to 92 and 95% relative humidities retarded the termination of diapause II.     

The influence of juvenile hormone on the feeding behaviour of last instar larvae of the codling moth,Laspeyresia pomonella (Lep., Tortricidae), reared under different photoperiods

Summary Duration of the feeding stage and corresponding weight increase during the last larval instar of the codling moth,Laspeyresia pomonella, are controlled by JH. Larvae reared under short day conditions have a relatively high titer of JH during the last larval instar and enter diapause as mature larvae. They feed longer and become heavier than larvae reared under long day conditions, which have no JH during the last larval instar and pupate when mature. By application of the JH mimetic Altosid^® during the first 2 or 3 days of the last larval instar, the duration of feeding activity of larvae reared under respectively long and short day conditions was prolongated and the larvae became significantly heavier. The feeding behaviour could only be influenced by the juvenoid as long as the feeding activity of the larvae had not yet ceased.     

Influence of larval diapause on pheromone communication in the khapra beetle,Trogoderma granarium everts

Summary InTrogoderma granarium, induction of larval diapause by sub-optimal temperature enhanced the efficiency of pheromone perception by adult males. Such diapause also altered the pattern of pheromone production by females.     

Phytoalexin response is elicited by a pathogen (Rhizoctonia solani) but not by a mycorrhizal fungus (Glomus mosseae) in soybean roots

Summary A container system was constructed to study the response of soybean roots to infection by mycorrhizal or pathogenic fungi. The system allows a rapid and synchronous inoculation byGlomus mosseae orRhizoctonia solani. The phytoalexin glyceollin was measured in roots of inoculated and uninoculated plants for a period of 30 days. A significantly increased content of phytoalexin was found inR. solani-infected roots as compared to uninfected control roots. However, there was no difference in the glyceollin contents of the mycorrhizal and the control roots for up to 23 days after inoculation. The accumulation of glyceollin inR. solani-infected roots was not influenced by a subsequent inoculation withG. mosseae. Moreover glyceollin accumulated in mycorrhizal plants to the same extent as in control plants when they were inoculated withR. solani. The two fungi did not mutually influence the course of infection when they were inoculated together.     

Two mechanisms in the biological clock ofPieris brassicae L.: an oscillator for diapause induction; an hour-glass for diapause termination

Summary Resonance experiments for photoperiodic termination of pupal diapause demonstrated thatPieris brassicae uses a night-measuring hour-glass mechanism. In previous work the same resonance technique for diapause induction revealed that photoperiodic time-measurement is a function of the circadian system. For the first time in a living organism it has been shown that the biological clock operates by means of an oscillator for photoperiodic onset of a phenomenon and according to an hour-glass system for photoperiodic termination.     

Mixed life cycles in the transitional zone between voltinisms in the fall webworm,Hyphantria cunea

The fall webworm,Hyphantria cunea Drury, was introduced from North America into Japan at half a century ago. At present, the populations north of 36° N are bivoltine and those south of 36° N are trivoltine. In the present study, the life cycle in the transitional zone between voltinisms was clarified in Tsukuba (36.1° N). When fourth instar larvae of the second generation were collected in the field and maintained in the laboratory, the incidence of pupal diapause increased when the sampling date was delayed from 16 August to 5 September. The fact that some developed without diapause inidcates the occurrence of a trivoltine life cycle in this locality, where a bivoltine life cycle is predominant. The critical photoperiod for diapause induction at 20 and 25°C was 14 h 13 min and 14 h 10 min, respectively. The photoperiodic response may explain the rapid increase in diapause incidence in late summer. In laboratory-reared diapause pupae, the time and period of chilling (5°C) greatly influenced the time required for adult emergence at the final incubation temperature of 25°C. However, diapause pupae chilled for a sufficiently long period developed to adulthood rapidly, irrespective of the conditions before chilling. Therefore, the difference in timing of entering diapause between pupae of the second and third generations would not result in their temporal reproductive isolation in the following spring. It is concluded that the mixed voltinism in Tsukuba is not a result of a mixture of genetically distinct bivoltine and trivoltine populations, but a result of the phenotypic plasticity in a genetically rather homogeneous population.     

Demonstration of a Na+−K+−Mg2+ dependent ATPase in a preparation from hindgut and malpighian tubules of two species of insect

Zusammenfassung Die Präsenz einer charakteristischen Na⁺–K⁺-aktivierbaren ATPase (E.C. 3.6.1.3) wurde erstmals in einer mikrosomalen Fraktion des Enddarmes und der malpighischen Gefässe bei der WüstenschreckeScistocerca gregaria und der LaubheuschreckeJamaicana flava nachgewiesen.     

Delayed metamorphosis and diapause in the sugar cane borerDiatraea saccharalis

Summary The problem of arrested or delayed development was examined in the sugar cane borer,Diatraea saccharalis. It was found that the insect can either enter diapause or exhibit a period of delayed metamorphosis according to the photoperiod conditions prevailing. We have observed the development characteristics ofD. saccharalis and conclude that a distinction should be made between a delayed metamorphosis phase and a diapause stage.This work was supported by a grant from NSERC.     

Haemolymph ecdysteroids level following the injection of ecdysone or ecdysterone; its relation with tegument and midgut response inAeshna cyanea (Insecta,Odonata)

Summary The haemolymph ecdysteroid level after injection of ecdysone or ecdysterone inAeshna cyanea larvae has been determined by a radioimmunoassay method. The rate of excretion appears to be dependent on both the ecdysteroid injected and the time of injection. In case of ecdysone injection, the secretion of the epidermis cuticle and the differentiation of the imaginal midgut epithelium occur when the ecdysteroid level remains low for many days.     

Thermoperiodically induced diapause in a mite in constant darkness is vitamin A dependent

Summary By rearing the predacious miteAmblyseius potentillae in a daily temperature cycle in constant darkness it could be shown that diapause may be thermoperiodically induced. When the same experiments were performed using diets without vitamin A it appeared that vitamin A is necessary to achieve a state of reproductive diapause in this mite.2 February 1987     

Isolation of the insect paralyzing agent coniine fromSarracenia flava

Summary As part of a study to clarify the relationship between insects and the insectivorous plantSarracenia flava, we have observed the presence of the paralyzing agent coniine in the volatile constituents. Fire ants have been used as the test organism in bioassay studies for paralyzing activity.Acknowledgment. This work was financed in part by the National Institutes of Health (Grant No. CA 13268). Thanks go to Dr.Sidney McDaniel for collection of the plant material and to Mr.Peuman Neel for assisting in the project.     

Residual influences on fecundity in drosophilid species

Summary A residual influence of males and females on oviposition has been examined in 7 drosophilids. There was evidence for oviposition deterrence inDrosophila funebris, with males as well as females producing the inhibitory effect. In contrast, male residues stimulated oviposition inZaprionus tuberculatus. Male residues also stimulated oviposition and appeared to serve as an aggregation cue inD. melanogaster.     

Age-dependent tolerance toBaculovirus in last larval instars of the codling moth,Cydia pomonella,L., induced either for pupation or for diapause

Summary LD₅₀ values as well as time-dependent parameters of granulosis virus infections were determined at different times during the last larval instar (L₅) of the codling moth,Cydia pomonella L., induced either for pupation or for diapause. A significant increase of tolerance to virus was found in 48-h-old L₅ induced for pupation, and 24 h later in L₅ induced for diapause.     

Arylpyridyl-thiosemicarbazones: A new class of anti-juvenile hormones active against Lepidoptera

Summary A new class of anti-juvenile hormone agents is described. Active anti-juvenile hormone compounds were either diazine thiosemicarbazones or aryl substituted pyridyl thiosemicarbazones, synthesized from substituted benzaldehydes. While many analogs in these classes showed feeding and growth inhibition in a variety of insects, a select group caused formation of precocious pupal characteristics inAgrotis ipsilon (black cutworm) andHeliothis virescens (tobacco budworm) and black cuticle and precocious pupae inManduca sexta (tobacco hornworm). They were active only by diet incorporation. The symptoms of precocious development could be reversed by co-administration of a juvenoid. One of the active compounds was shown to inhibit juvenile hormone biosynthesis in vitro by corpora allata of the cockroachDiploptera punctata. However, none of the compounds were active inhibitors of purified chicken liver prenyl transferase.     

Intergeneric interactions betweenEimeria separata (Apicomplexa) andNippostrongylus brasiliensis (Nematoda) in the rat

Summary Ova production inNippostrongylus brasiliensis infected rats was significantly greater than in rats singly infected with the helminth whenEimeria separata infections were introduced 4, 6 and 11 days postinoculation withN. brasiliensis. Patent periods were unaltered during concurrent infections. These results suggest that the presence ofE. separata affects helminth fecundity but does not increaseN. brasiliensis longevity as has been shown withE. nieschulzi.This study was supported by NIH MB RS Grant RRO8012-8.