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PubMed2005

Effect of temperature on the termination of prolonged larval diapause in the chestnut weevil Curculio sikkimensis (Coleoptera: Curculionidae).

Adults of the chestnut weevil Curculio sikkimensis emerged over a 3-year period under laboratory and quasi-field conditions due to a prolonged diapause that occurred at the mature larval stage. Variable proportions of the larvae remained in diapause after a single cold (5 degrees C) treatment of 120 days. Extension of the chilling period to as long as 540 days did not increase the percentage of diapause termination, and excessively long chilling actually reduced the percentage. Chilling was not indispensable to the termination of larval diapause. Diapause intensity was very high and variable, and more than 1000 days at 20 degrees C was necessary to reactivate all diapause larvae. When the diapause larvae were exposed to cycles of low (5 degrees C for 120 days) and high (20 degrees C for 240 days) temperatures, the percentage of diapause termination reached 100% after two or three such cycles. Thus, the prolonged diapause of C. sikkimensis has characteristics similar to the common short winter diapause in other insects, but has unique characteristics that ensure polymodal reactivation over several years.

Adaptation, Physiological↗
PubMed2006

Distinct effects of different temperatures on diapause termination, yolk morphology and MAPK phosphorylation in the silkworm, Bombyx mori.

Previously, we showed that chilling of diapausing Bombyx eggs activated ERK/MAPK in yolk cells coincidentally with acquisition of developmental competence, and that ERK regulates diapause termination via activating transcription of key enzyme genes for ecdysteroid and sorbitol metabolism. To further elucidate the molecular mechanisms of temperature signaling and diapause termination, effects of different temperatures on diapause termination, yolk morphology, and ERK and p38 MAPK phosphorylation were analyzed. We confirmed the coincidence of diapause termination and changes of phosphorylated levels of ERK and p38 MAPK at various temperatures. Our study also shows that different temperatures have distinct effects on diapause termination and yolk morphology, however, these two effects did not always coincide. Our analyses suggest the possibility that the effects on diapause termination and yolk morphology are independently regulated by ERK. We observed that a temperature shift alters diapause intensity reversibly, and coincidental changes of phosphorylated ERK levels suggest that ERK may have a role in regulating the diapause intensity. The present study suggests that ERK and p38 MAPK have roles for transmitting the temperature signals that are important for diapause termination.

Animals↗
PubMed2002

Possible involvement of ecdysteroids in embryonic diapause of Locusta migratoria.

In the Ibaraki population (Japan) of Locusta migratoria, adult locusts produce diapause eggs under short-day (SD) conditions and non-diapause eggs under long-day (LD) conditions. The identity and titre of ecdysteroids in the ovaries and eggs from LD and SD adult females were investigated by RIA/HPLC. Maternal ecdysteroids accumulated in the developing ovaries represented about 90% polar conjugates, 5% free ecdysteroids and 5% non-hydrolyzable metabolites. Before oviposition the quantity of ecdysteroids reached 29.8+/-1.85 ng 20-hydroxyecdysone equiv. per mg tissue ovaries from LD females and 13.1+/-3.55 ng 20E equiv./mg in ovaries from SD females. The sum of RIA-positive materials in newly laid eggs was more than three times higher in non-diapause eggs than in diapause eggs. Ecdysteroids present in egg extracts comprised about 85% polar conjugates, 5% free ecdysteroids and 10% non-hydrolyzable metabolites. On the other hand, after diapause termination the amount of ecdysteroids increased drastically. Also, the composition of ecdysteroids differed from that observed during diapause and became comparable to that of non-diapause eggs. The significant differences in the ecdysteroids between non-diapause and diapause eggs may suggest the possible involvement of these compounds in the control of embryonic diapause of this locust.

Journal Article↗
PubMed1997

A Role for Ecdysteroids in the Induction and Maintenance of the Pharate First Instar Diapause of the Gypsy Moth, Lymantria dispar.

Several lines of evidence suggest a novel regulatory mechanism for diapause regulation in the gypsy moth. We propose that ecdysteroids play a role in the induction and maintenance of the pharate first instar larval diapause in this species. A 55 kDa gut protein that is indicative of diapause is expressed in intact and neck-ligated pharate larvae but is not expressed when a ligature is placed posterior to the prothorax, site of the prothoracic gland. Guts cultured in vitro for 12 h cease to synthesize the 55 kDa protein, but synthesis of the protein resumes if the culture medium is enriched with a prothorax extract from pharate larvae or a prothoracic gland extract from fifth instar larvae. Injection of 20-hydroxyecdysone or the ecdysteroid agonist, RH-5992, into isolated abdomens stimulates synthesis of the diapause-specific 55 kDa protein, suggesting that the essential factor from the prothorax is an ecdysteroid. KK-42, an imidazole derivative known to inhibit ecdysteroid biosynthesis, averts diapause when applied to prediapausing pharate first instar larvae, but this effect can be countered by application of 20-hydroxyecdysone or RH-5992, i.e. KK-42 treated pharate larvae that are exposed to an ecdysteroid or RH-5992 readily enter diapause. A chilling period (120 days at 5 degrees C) is normally adequate to prompt an immediate termination of diapause when pharate larvae are transferred to 25 degrees C, but if such larvae are held in hanging drop cultures with ecdysteroids they fail to terminate diapause. Together, these results suggest that ecdysteroids are essential for the induction and maintenance of diapause and imply that a drop in the ecdysteroid titer is essential for diapause termination. Copyright 1997 Elsevier Science Ltd. All rights reserved

Journal Article↗
PubMed1997

Photoperiodism and control of summer diapause in the Mediterranean tiger moth Cymbalophora pudica.

Photoperiodic responses to both constant and changing photoperiods were studied in the Mediterranean tiger moth Cymbalophora pudica. Embryos, larval instars and prepupae were all sensitive to photoperiod, and the responses of larvae and prepupae to changing photoperiods were similar. At 23+/-2 degrees C, constant 24-h photoperiods with short photophases (11, 12h) induced a long diapause (mean 88days) whereas long photophases (14, 16h) induced a short diapause (mean 52days). A change to a longer or shorter photophase during larval development or during diapause caused a significant extension (up to a maximum of 138days) or shortening (down to a minimum of 10days) of diapause, respectively, but only when at least one of the photophases was longer than 14h. Thus, shortening and prolongation of photophase had an opposite effect than constant short and long photophases, respectively. Changes within the range of photophases of 10-14h did not cause a significant change in diapause duration.Experimental results enabled us to outline the mechanisms regulating voltinism and the duration of summer diapause. For the monovoltine cycle, cold autumn/winter temperatures slow down larval development, and prepupal aestivation starts relatively late (March, April). Prepupae are then kept in diapause by the increasing daylength (>14h after late April). Pupation is synchronized by decreasing daylength after summer solstice, and imagoes emerge in September/October. For the bivoltine cycle, when the autumn/winter temperatures are relatively warm, a certain portion of the population (depending on the individual rate of growth) may be diverted to a bivoltine life-cycle. In such a case, larval development is fast and short enough to allow an early start of diapause (prior to or during February). The duration of such early diapause is not influenced by changes in daylength (<14h); pupation occurs very early (April/May), and spring generation imagoes fly and oviposit in May/June. Summer larvae and prepupae live under decreasing daylength (>14h), which shortens their diapause to 20-30days. Imagoes of the autumnal generation thus occur in September/October, together with the univoltine portion of the population.

Journal Article↗
PubMed1997

Summer and winter diapause in pupae of the cabbage butterfly, Pieris melete Ménétriés.

The cabbage butterfly, Pieris melete is multivoltine with a pupal summer and winter diapause. Summer and winter diapause are induced principally by relatively long and short daylengths, respectively. The intermediate to relatively short daylengths of autumn permitted some pupae to develop without diapause in the field. A short daylength had a stronger diapause inducing effect than a relatively long one under higher temperatures. The principal sensitive phase for photoperiodic response occurred before the late 3rd larval instar. The critical daylength for wild autumnal populations was between 12h 30min and 12h 40min at an average temperature of 20.5 degrees C. A night interruption by 2h of light averted diapause most effectively when it was placed 10 to 12h after lights-off. High temperatures and long days during summer inhibited the incidence of diapause, suggesting that the occurrence of summer diapause is due to the specific climatic conditions occurring in April and early May, rather than to the high temperatures in summer. This indicates that the butterfly has a cryptic ability to reproduce in summer. High temperatures delayed diapause development, whereas low temperatures enhanced it, indicating that the optimum temperature of diapause development is lower. The diapause regulating mechanisms thus ensure that the species synchronises its development and reproduction with the growth seasons of the host plants and provide the species with a high degree of flexibility in its life cycle.

Journal Article↗
PubMed1998

Response to photoperiod during diapause development in the spider mite Tetranychus urticae.

To study the question whether photoperiodic time measurement in the spider mite Tetranychus urticae is based on a qualitative or quantitative principle, the duration of diapause development was determined in individual females at various constant photoperiods at 19 degrees C. Diapause duration at all four long-night treatments fluctuated around 64.5 days, varying from 62.2 at LD 12:12h to 66.4 at LD 10:14h. The within-treatment variation in diapause duration of the long-night groups appeared to be significantly correlated to the nightlength of the photoperiods used; the longer the nightlength, the higher the within-treatment variation. Frequency distributions of females completing diapause under the two regimes with nightlengths near the critical nightlength were skewed to the right. Mean diapause durations at these regimes, LD 13:11h and LD 14:10h, were 25.4 and 11.9 days, respectively. Mites completed diapause rapidly and synchronously under the three short-night photoperiods tested; within two weeks after transfer from cold storage at 4 degrees C to the diapause terminating regimes at 19 degrees C all females started reproduction. Mean diapause durations were 8.1, 6.4 and 6.5 days for the short-night treatments LD 15:9h, LD 17:7h and LD 19:5h, respectively. The coefficients of variation of diapause duration (variability within groups relative to the mean) of the short-night and the long-night groups varied from 18 to 42%; the coefficients of the two intermediate groups were 69and 81%. There was a clear difference in diapause duration between long-night and short-night groups, but no significant difference was present in this characteristic between different long-night groups on the one hand and only a small difference between different short-night groups on the other. These results support the hypothesis that photoperiodic time measurement in the spider mite is based on a qualitative principle; photoperiods are classified as either 'long' or 'short' in relation to a 'critical' photoperiod. However, around the critical nightlength, intermediate responses were observed which might hint at the quantitative nature of the underlying mechanism. Therefore, although most results are in agreement with the hypothesis of a qualitative mechanism, it cannot be excluded that photoperiodic time measurement in the spider mite is based on a quantitative principle.

Journal Article↗
PubMed1999

Diapause-associated transcription of BmEts, a gene encoding an ETS transcription factor homolog in Bombyx mori.

To understand the molecular mechanism of diapause determination in early embryogenesis of the silkworm, Bombyx mori, mRNA from diapause and non-diapause eggs was compared using the differential display technique. A 1.2 kbp differentially amplified cDNA fragment was cloned and sequenced. Northern blot analysis confirmed that the mRNA corresponding to this clone, D1, was specifically induced in diapause eggs from 20 h after oviposition, and decreased gradually but was clearly detectable until 40 days after oviposition. On the other hand, if diapause eggs were activated by HCl treatment 20 h after oviposition, the mRNA corresponding to D1 vanished 72 h after HCl treatment. In pnd (pigmented and non-diapausing egg) homozygous embryos, which never enter into diapause, the RNA was not transcribed at any stage, whereas, in pnd-2 homozygous embryos which also have no diapause, similar results were obtained to those for HCl treated eggs. The deduced amino acid sequence of D1 was most highly related to the identified Drosophila and vertebrate ETS proteins, within the approximately 85 amino acid ETS domain. ETS proteins play an important role in transcription activation during a variety of biological processes and can be grouped into sub-families, based on sequence similarity in the ETS domain which has been shown to be a DNA-binding domain. Therefore, we have called the gene corresponding to D1 BmEts. These observations suggest that BmEts encodes a novel ETS family member which is strongly associated with the embryonic diapause. Moreover, BmEts probably acts downstream of the pnd gene in the regulatory hierarchy of diapause determination, alternatively BmEts itself might be the pnd gene.

Amino Acid Sequence↗
PubMed2006

Prolonged diapause in the ectoparasite Carnus hemapterus (Diptera: Cyclorrhapha, Acalyptratae) - how frequent is it in parasites?

Prolonged diapause is usually interpreted as an adaptation to unpredictable environmental conditions and resource availability. Many parasites usually face highly unpredictable environments, therefore prolonged diapause should be common among these organisms. Here we examine the occurrence and frequency of prolonged diapause in the ectoparasite Carnus hemapterus (Diptera: Cyclorrhapha, Acalyptratae). We found that the studied population is polymorphic with respect to diapause duration. Emergence of carnid flies after 2 and 3 wintering seasons was therefore detected in around 17% and 21% of the samples respectively. The number of flies with prolonged diapause ranked 0.88-50% with respect to the number of flies emerging during the first spring. Both the occurrence of prolonged diapause and the number of flies with a long life-cycle are related to the number of flies emerging during the first spring. The emergence pattern of flies with prolonged diapause was very similar to that observed for flies with a short cycle and occurred in synchrony with the occurrence of hosts. Prolonged diapause has been frequently reported in plant-feeding insects and in some host-parasitoid systems, but this is, to our knowledge, the second report ever on prolonged diapause in true parasites of animals. We discuss the reasons for the apparent rarity of prolonged diapause among these organisms.

Adaptation, Physiological↗
PubMed1986

Cellular changes in the prothoracic glands of diapausing pupae of Manduca sexta.

Prothoracic glands from diapausing pupae of the tobacco hornworm, Manduca sexta, synthesize markedly less ecdysone in vitro in response to prothoracicotropic hormone (PTTH) than do glands from non-diapausing pupae. Impaired steroidogenesis is also observed in glands from diapausing animals exposed to agents that enhance ecdysone synthesis in non-diapausing pupal glands by increasing intracellular levels of cAMP (1-methyl-3-isobutylxanthine, dibutyryl cAMP, and the calcium ionophore A23187). In contrast, prothoracic glands from diapausing pupae synthesize significantly more cAMP in response to PTTH and A23187 than do those from non-diapausing pupae. These observations indicate that the PTTH-refractoriness characteristic of prothoracic glands during diapause results from a lesion in the steroidogenic pathway occurring beyond the level of the PTTH receptor-adenylate cyclase system. The diapause condition of the prothoracic glands (reduced ecdysone synthesis accompanied by enhanced cAMP formation) can be mimicked by extirpation of the brain of a non-diapausing pupa. Thus, cellular changes in the prothoracic glands associated with diapause may arise as a result of the absence of some factor produced by the pupal brain (e.g. PTTH).

1-Methyl-3-isobutylxanthine↗
PubMed2005

Neuroendocrine roles of the brain in the regulation of 20-hydroxyecdysone responsiveness in two types of diapause pupae of the cabbage armyworm, Mamestra brassicae.

The cabbage armyworm, Mamestra brassicae, has winter-and aestival- diapause pupae (WD- and AD-pupae) showing differences in the strength of diapause. We tried to quantify diapause-strength by measuring the doses of 20-hydroxyecdysone (20-E) required to induce adult development in WD-, AD- and decerebrated non-diapause pupae (ND-pupae). The role of the brain in the regulation of diapause-strength was studied through the decerebration and brain-reimplantation of WD-and AD-pupae. The 20-E doses required for adult development were small within the first 2 days of pupation, and increased thereafter to reach a constant level about 10 days after pupation in AD- and decerebrated ND-pupae. The required 20-E doses in WD-pupae increased for more than 40 days after pupation. When 0-day-old WD- and 0-day-old AD-pupae were decerebrated, required 20-E doses increased after pupation and reached a constant about 10 days later. The required 20-E dose reached a constant level in decerebrated WD-pupae that was smaller than that observed for decerebrated ND- and WD-pupae. Furthermore, the required doses increased when 0-day-old WD-pupal brains were reimplanted into decerebrated WD- and decerebrated ND-pupae. In WD-, AD- and decerebrated ND-pupae, diapause-strength can be represented as the 20-E dose required for adult development. Diapause-strength is weak after pupation, increases thereafter, and reaches a constant about 10 days later in AD- and decerebrated ND-pupae. In WD-pupae, diapause-strength increases for more than 40 days after pupation and reaches a level that is twice that estimated for AD-pupae. Brains of diapausing WD-pupae may secrete a factor that suppresses the 20-E responsiveness of pupal organs, for the purpose of maintaining winter-diapause.

Animals↗
PubMed1998

The evolution of diapause in a coupled host-parasitoid system.

Diapause of part of a population during a breeding opportunity is widespread among insects. We explore the evolution of such diapause in a coupled host-parasitoid system, using a discrete-generation population dynamic model that incorporates diapause. We show that diapause in the host tends to be a stabilizing factor while diapause in the parasitoid does not affect the stability boundaries. We then allow the frequency of diapause in the host and parasitoid to evolve, and find the joint population and evolutionary dynamic equilibrium by numerical methods. At the equilibrium, population dynamics exhibit cycles and host diapause always occurs. Parasitoid diapause often occurs, though this depends on exact parameter values. Thus, intrinsically generated fluctuations in fitness (due to cyclical population dynamics) lead to the evolution of diapause as a bet-hedging mechanism.

Animals↗
PubMed2001

Diapause development in frozen larvae of the goldenrod gall fly, Eurosta solidaginis fitch (diptera: tephritidae).

Seasonal changes in metabolic rate and the potential for morphological development demonstrated that third-instar larvae of the goldenrod gall fly, Eurosta solidaginis Fitch, exhibit a distinct winter diapause. Metabolic rate (CO2 production) was significantly lower from 15 October to 9 February than in early autumn (9 September) and spring (1 March) samples. The induction of diapause coincided with the development of cold-hardening, maximum larval mass, and gall senescence, but our experiments did not identify specific cues triggering diapause induction. We examined the influence of exposure to 0 degrees C and -20 degrees C on diapause development. Diapause development in larvae stored at 0 degrees C occurred at approximately the same rate as in nature. Until 15 December the larvae were in the refractory phase of diapause (incapable of morphological development, even at permissive temperatures), but afterward moved to the activated phase within which diapause intensity decreased until termination in February. Diapause development occurred in larvae collected during the winter and stored at -20 degrees C for periods of 1 week to 3 months. Diapause intensity decreased in frozen larvae through the winter but at a slower rate than in larvae stored at 0 degrees C.

Animals↗
PubMed2005

Diapause incidence in the two-spotted spider mite increases due to predator presence, not due to selective predation.

We recently reported evidence for increased diapause incidence in the spider mite Tetranychus urticae in presence of the predatory mite Typhlodromus pyri. This effect may arise from (1) selective predation on non-diapause spider mites, (2) predator-induced diapause in spider mites, or (3) both. Using a different strain of T. urticae, we first recovered increased diapause incidence in association with predators. Then, we tested for selective feeding in two-choice experiments with equal numbers of non-diapause and diapause spider mites. We found that the predatory mite had a significant preference for the latter. This indicates that increased diapause incidence in association with predatory mites is not due to selective predation. Therefore, predator-mediated physiological induction of diapause seems a more likely explanation. The cues leading to induction appear to relate to the predators, not their effects, since predation simulated by spider-mite removal or puncturing did not significantly affect diapause incidence. Why spider mites benefit from this response, remains an open question.

Adaptation, Physiological↗
PubMed2004

Predation risk affects diapause induction in the spider mite Tetranychus urticae.

Whenever diapause induction triggers movement into another microhabitat or the development of protective morphological structures, this may also alter predation risk. If the risk of being eaten is lower in the diapause phase, then there may be selection favouring diapause induction in response to predators or their cues. In this article, we studied the effect of the predatory mite Typhlodromus pyri on diapause induction in the spider mite Tetranychus urticae. We used a Greek strain because under long-night photoperiods and low temperature only part of the population enters diapause, thereby leaving room for the impact of another factor. In spider mite groups under predation, the percentage diapause induction increased whenever night-lengths were such that diapause was induced (13-16 h of night). Given this diapause induction in response to predation risk, the question arises whether entering diapause helps spider mites to escape from predation and contribute more offspring to the spring generation next year.

Adaptation, Physiological↗
PubMed1990

Photoperiodic diapause in Drosophila melanogaster involves a block to the juvenile hormone regulation of ovarian maturation.

Females of Drosophila melanogaster held under short-day photoperiods at a moderately low temperature (12 degrees) enter a state of ovarian diapause in which yolk deposition in the oocytes is suspended (D. S. Saunders, V. C. Henrich, and L. I. Gilbert, Proc. Natl. Acad. Sci. USA 86, 3748-3752, 1989). An enzyme-linked immunosorbent assay (ELISA) using polyclonal antibodies raised against D. melanogaster yolk polypeptides (YPs) showed that diapausing flies synthesize and accumulate YPs in the hemolymph, but very little in the ovary. Nondiapausing females at the same temperature but at long days, and short-day flies in which diapause was broken by an upshift in temperature or topical application of juvenile hormone (JH), showed enhanced titers of YPs in the ovaries, suggesting stimulating uptake. Determinations of juvenile hormone bisepoxide (JHB3) and JH III synthesis in vitro by single excised corpora allata showed that glands from nondiapausing flies or corpora allata from flies in which diapause had been broken synthesized JH at a rate about four times higher than glands from diapausing flies. Corpora allata incubated in medium supplemented with farnesoic acid showed an increase in the rate of JH synthesis, but the increase was relatively greater with corpora allata from nondiapausing flies. Glands from diapausing flies presented the appearance of newly emerged or "immature" glands. Ovarian diapause is terminated at 12 degrees LD 10:14 in 7 days following topical application of either JH III or JHB3 at a concentration of about 0.5 micrograms per fly, diapause termination being expressed by an increased rate of vitellogenesis and by an increase in the number of fully developed eggs per vitellogenic female. It is concluded that the short-day-elicited diapause in D. melanogaster results from a "block" to the JH-stimulated uptake of yolk proteins from the hemolymph, caused by a reduced rate of JH synthesis by the corpus allatum. Photoperiodic regulation of the corpus allatum may be mediated via the brain.

Animals↗
PubMed2005

DaTrypsin, a novel clip-domain serine proteinase gene up-regulated during winter and summer diapauses of the onion maggot, Delia antiqua.

Diapause prepares insects and other arthropods to survive in harsh environments. To explore the molecular basis of winter (WD) and summer diapauses (SD), we screened for diapause-specific genes in the onion maggot, Delia antiqua, that diapauses as a pupa in both summer and winter. A diapause-induced transcript, DaTrypsin, was identified through differential display, and examined by Northern blot, quantitative real-time PCR and sequence analyses. The full-length cDNA, 1379 bp long, encodes 384 a.a. with a molecular mass of 43,005 Da. The protein contains a 20-a.a. secretion peptide, followed by an amino-terminal clip domain and a carboxyl-terminal serine proteinase domain. With Ser, His and Asp as catalytic residues and Asp, Gly and Ser as specificity determinants, DaTrypsin is anticipated to be a trypsin-like enzyme. DaTrypsin transcription is up-regulated in both SD and WD pupae with higher mRNA levels during WD than SD. Heat shock further elevated gene transcription in both SD and WD pupae, whereas cold shock reduced DaTrypsin expression in SD pupae and had no significant effect on WD pupae. In SD pupae, DaTrypsin transcripts gradually build up during diapause, and after temperature shocks, whereas in WD pupae DaTrypsin mRNA levels are high at the beginning of diapause and immediately after a temperature shock and then gradually decrease with time. DaTrypsin represents the first serine proteinase gene expressed during diapause as well as the first gene up-regulated in both SD and WD. It may participate in the host's immune defense and/or maintain the developmental status in the diapausing pupae.

Adaptation, Physiological↗
PubMed2005

Relationship between an increase of juvenile hormone titer in early instars and the induction of diapause in fully grown larvae of Sesamia nonagrioides.

The larvae of Sesamia nonagrioides (Lepidoptera: Noctuidae) grown at 25 degrees C and long photoperiod (16:8h light:dark) pupate in the 5th or 6th (mostly) larval instar, while the larvae reared under a short photoperiod (12:12h) enter diapause during which they consume some food and undergo up to 12 (usually 3-4) stationary larval molts. Diapause programming includes an increase of juvenile hormone (JH) titer in the hemolymph from about 20 to 50 nM in the 4th and 5th instar larvae (titer in earlier instars was not measured). JH I, II, and III are present in approximate ratio 1-2:10:1. The JH titer drops to zero before pupation but remains around 20 nM during diapause. Perfect extra larval molts associated with a body weight increase can be induced in the non-diapausing larvae with a JH analogue (JHA). The weight rise is due to accumulation of reserves and not to a general body growth. The timing of extra molts is similar to the molting pattern of the diapausing larvae only when JHA is present since early larval instars. In the diapausing larvae, JHA application affects neither molting periodicity nor the body weight. It is concluded that (1) Increased JH titer in early larval instars is a part of diapause programming; (2) The extension of larval stage in the diapausing larvae, but not the timing pattern of extra molts, is due to continuously high JH titer; (3) The diapause program includes low food intake, maintenance of a certain body weight, and periodic larval molts.

Animals↗