Adult diapause ofCybocephalus nigriceps nigriceps [Col.: Cybocephalidae]

During autumn and winter (October–February)Cybocephalus nigriceps nigriceps (J. Sahlberg) adults undergo a facultative diapause. The diapausing adults agregate in hiding places, development of the ovaries is arrested, and prey consumption is lowered. Diapause can be prevented by exposure to a long-day photoperiod (16 hr light) at high temperatures (29° and 32°C). Diapause is induced mainly by short-day conditions, but the termination of diapause is affected by both photoperiod (long-day conditions) and temperature (29°, 32° and 34°C). In mature females, diapause induction causes ovarian degeneration. The induction or inhibition of adult diapause is affected by photoperiods occurring during larval development as well as during adult life.     

Photoperiodic control of adult diapause in the predacious mite, Amblyseius potentillae: repeated diapause induction and termination

ABSTRACT. Photoperiodic control of facultative reproductive diapause was examined in females of the phytoseiid mite, Amblyseius potentillae (Garman). Full diapause was induced by rearing the mites from egg to adult under short-day photoperiods. Egg-laying females, however, which had experienced a long-day photoperiodic regime during pre-imaginal development, could still be induced to enter diapause when they were transferred to a short-day regime. Diapause development proceeded slowly under a short-day photoperiod, but was accelerated under long days. During diapause development under short days the photoperiodic sensitivity of the females diminished gradually and ultimately disappeared completely. However, after completion of diapause, sensitivity to photo-period reappeared. A second diapause could be induced in post-diapause females under short-day photoperiods and completed again under long-day photoperiods. These results show that A. potentillae remains sensitive to diapause-inducing and diapause-averting daylengths during the adult stage and that a second diapause may be induced after completion of the first one.     

Hormonal control of seasonal morphs by the timing of ecdysteroid release in Araschnia levana L. (Nymphalidae: Lepidoptera)

Araschnia levana L. occurs in two seasonal morphs. Larvae reared under short-day conditions become diapause pupae and emerge as red spring-morph butterflies. Long-day larvae become non-diapause pupae, which emerge as black and white summer morphs. Pupae reared under these different conditions were joined in parabiosis. Both underwent adult development without diapause and the long-day animals developed into the summer morph as normal. The morph of short-day animals depended on the time of parabiosis. When they were joined to fresh long-day pupae 1 day after their own pupation, summer morphs resulted. When parabiosis began 4 days after pupation or later, spring morphs resulted. Extirpation of the brain-corpora cardiaca-allata complex from long-day pupae affected neither non-diapause development nor the summer morph. Adult development could be prevented by removal of head and prothorax. When adult development was initiated in the remaining bodies by 20-hydroxyecdysone 14 days after pupation, the spring morph resulted.—Injection of 20-dydroxyecdysone into 3-day-old short-day pupae initiated adult development and led to the summer morph. Injections into 10-day-old short-day pupae led to the spring morph. The same was true in diapause pupae deprived of their brain-corpora cardiaca-allata complex. These results indicate that seasonal diphenism in A. levana is controlled only by the timing of ecdysteroid release, which initiates adult development. There is no direct influence of the brain on wing coloration.     

Larval diapause in the mosquito aedes triseriatus: effects of diet and temperature on photoperiodic induction

Larval diapause was induced in both a northern (Ohio) and a southern (Alabama) strain of Aedes triseriatus by photoperiodic treatment of the larval stage itself. The effect of a short-day (10 hr) photoperiod during larval development was cumulative and resulted in failure of the fourth instar to pupate. The larvae, which had been obtained from long-day (16 hr) eggs, underwent diapause when their development was slowed by a low-quantity diet or low temperature (16°C) for a sufficient number of days to allow the short-day photoperiod to exert a visible effect.     

Induction of reproductive diapause via perception of photoperiod through the compound eyes in the adult blow fly, Protophormia terraenovae

Covering and surgical removal of the compound eyes were performed to localize photoreceptors for photoperiodic responses in the blow fly Protophormia terraenovae (Diptera, Calliphoridae). Adult females showed a long-day photoperiodic response to control reproductive diapause. When the compound eyes were bilaterally covered with silver paint, diapause incidence increased under diapause-preventing conditions, i.e., a long-day photoperiod and constant light, as though flies were kept under constant darkness. Neither silver painting on a medial region of the head capsule nor control painting in which both compound eyes were painted in a clear solvent caused significant effects on diapause incidence. Unilateral painting of the compound eye caused an increment of diapause incidence under constant light but no effects under a long-day photoperiod. When the compound eyes were bilaterally removed, all the flies developed their ovaries both under a long-day and a short-day photoperiod. Unilateral removal of the compound eye also caused ovarian development under a short-day photoperiod, whereas removal of one antennal lobe or all ocelli caused no effects on diapause incidence. Since P. terraenovae completely lost responsiveness to photoperiod after blinding of the compound eyes, it is likely that this fly perceives photoperiod through its compound eyes. Accepted: 18 February 1997     

Photoperiodic Control of Developmental Diapause in Nymphs of Prostriate Ixodid Ticks (Acari: Ixodidae)

Extrinsic control of developmental diapause in nymphs of prostriate ticks of the subgenus Ixodes sensu stricto (Ixodes ricinus and Ixodes persulcatus from Eurasia and Ixodes scapularis from North America) appears to be based on a complex two-step photoperiodic reaction of a short-day/long-day type. Diapause control in the subgenus Afrixodes (the South African tick Ixodes rubicundus) appears to be based on a simple long-day reaction. The option between non-diapause development and diapausing arrest in engorged nymphs is determined by both pre- and post-feeding photoperiodic regimes. Consequently diapausing arrest in engorged nymphs of Ixodes sensu stricto can be induced either by a short-day (after their engorgement) or by a long-day regime (in unfed nymphs), while active, non-diapause development is possible only when the short-day pre-feeding regime is followed by a long-day post-feeding regime. The photoperiodic response in I. (Afrixodes) rubicundus nymphs seems to be of the long-day type both before and after feeding. Consequently this non-diapause development is enabled by a long-day regime, while diapause is induced by a short-day regime of exposure. Nevertheless, there are some indications that the control of nymphal diapause in the latter species is also of a complex nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

The seasonal development cycle of <Emphasis Type="Italic">Aphantopus hyperantus</Emphasis> (L.) (Lepidoptera,Nymphalidae: Satyrinae) in Leningrad Province

The simultaneous influence of the photoperiodic and temperature conditions on pre-diapause and postdiapause larval development of the ringlet Aphantopus hyperantus was studied. At the short day (12 h of light a day) all larvae reached the III instar and entered diapause at all the temperatures tested (18–24°C). At the long day (22 h) the number of diapausing larvae increased with decreasing temperature, and the larvae diapaused at the III and IV instars. The I and II instar larvae (before winter) developed and grew faster under short-day, and the hibernated larvae, under long-day conditions. At the short day the growth rate of the I and II instar larvae did not depend on the temperature, and at the long day it decreased as the temperature increased. After hibernation the growth rate of the IV instar larvae increased with the temperature under long-day conditions, and did not depend on the temperature under short-day ones. Thus, acceleration or deceleration of development, depending on the photoperiodic and temperature conditions, regulated the timing of diapause in the overwintering stage (the III instar larva) and maintained the univoltine seasonal cycle. The males of A. hyperantus developed and grew faster than females while their weight at the larval and pupal stages was smaller. The thermal reaction norms for development (the lower temperature threshold and the coefficient of thermal sensitivity of development) were calculated for the eggs, IV and V instar larvae, and pupae. The coefficient of thermal sensitivity of development for the IV and V instar larvae taken together was lower, and the threshold was higher than the corresponding values for eggs and pupae. The thermal reaction norms for development of the latter stages were the same. The larvae of A. hyperantus retained their sensitivity to the photoperiod after hibernation. Resumption of development after cold reactivation occurred only under long-day conditions, whereas under short-day ones the overwintered larvae entered a repeated diapause. The possibility of photoperiodic reactivation and the absence of spontaneous resumption of development in these larvae were demonstrated.     

Diapause status of females affects attraction of male pear psylla, Cacopsylla pyricola, to volatiles from female-infested pear shoots

A companion study showed that male pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae) were attracted to volatiles from pear shoots infested with post-diapause females. The present study compared the behavioral response of males to diapause and post-diapause females. Assays were done using a Y-tube olfactometer. We collected male and female winterform psylla from pear orchards at regular intervals between late October (early diapause) and late February (post-diapause). Female-infested shoots were not attractive to males until the February samples, coinciding with ovarian maturation and onset of mating in the field. A second set of assays was done in which we manipulated diapause status in the laboratory either by exposing psylla to a long-day photoperiod or by treating insects with an insect growth regulator, fenoxycarb. In the photoperiod experiments, both short-day and long-day males preferentially selected long-day (post-diapause) females over short-day (diapause) females. Fenoxycarb-treated males preferred fenoxycarb-treated (post-diapause) females over untreated (diapause) females; untreated males showed no preferences. Results support observations made elsewhere that male winterform pear psylla perceive and are attracted to volatile odors associated with pear shoots infested with post-diapause females.     

Effects of precocene and methoprene application in young adult Musca autumnalis

Abstract Observations were made on the relative rates of growth among corpora allata, ovarian follicles and fat bodies in diapausing and reproductive Musca autumnalis DeGeer. Rates of corpora allata growth were greater in long-day than in short-day animals. Topically applied precocene II reduced the size of the corpora allata. Two sequential doses of precocene inhibited vitellogenesis. Topically applied methoprene produced vitellogenesis in short-day flies and inhibited development of hypertrophied fat body. This work provides evidence that Juvenile Hormone is the primary agent controlling diapause and non-diapause (vitellogenic) development in the ovaries of face flies.     

Control of diapause induction by a change in photoperiod in Melanoplus sanguinipes

The effect of photoperiod on diapause induction, developmental time and body size was examined in Melanoplus sanguinipes, the lesser migratory grasshopper. Contrary to what is found in most insects, facultative diapause-egg production is found to be controlled by changing rather than constant photoperiods. In addition, developmental time is shown to be faster under short-day photoperiods than long-day photoperiods. And finally, body size is larger under long-day photoperiods and smaller under short-day photoperiods. Implications of these results for the regulation of the seasonal life cycle of M. sanguinipes in the field are discussed.     

Induction of adult diapause and of low and high reproductive states in a parasitoid wasp,Ooencyrtus nezarae, by photoperiod and temperature

Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) was reared on eggs ofRiptortus clavatus (Thunberg) (Heteroptera: Alydidae) at various temperatures under long-day (L16:D8) or short-day (L10:D14) conditions. There was no diapause during egg, larval or pupal stages under any set of conditions examined. However, at 15°C under short-day conditions, vitellogenesis was arrested in all adult females and they entered diapause. At 15°C under long-day conditions, or at 20°C under short-day conditions, some adult females entered diapause. Under the latter set of conditions, the adult females laid eggs but they laid fewer eggs than under long-day conditions, Even at 25°C, under short-day conditions, adult females laid fewer eggs than under long-day conditions, and this low rate of oviposition was attributed to the retarded development of ovaries. Diapause adults reared at 15°C were more resistant to low temperature than nondiapause adults reared at 25°C.     

Aspects of the induction of diapause in a laboratory strain of the mite Tetranychus urticae

Some diapause characteristics were studied in a strain of the spider mite. Tetranychus urticae. which had been reared on bean plants in the laboratory for over 15 yr. The diapause induction response curve was of the long-day type, showing a sharply defined critical daylength of 13 hr 50 min. In constant darkness no diapause induction occurred, but with a photoperiod of 1L:23D diapause incidence was already complete. A thermoperiod with a 5°C amplitude induced diapause in combination with a short-day photoperiod only when the low phase of the thermoperiod coincided with the scotophase. The same thermoperiod did not induce any diapause in constant darkness. The photoperiodic reaction of the laboratory strain used in these experiments appeared to remain constant over a very long period of time and to be independent of the diapause history of previous generations of mites.Although photoperiodic sensitivity was demonstrated during the whole postembryonic development, sensitivity was maximal at the end of the protonymphal instar and declined rapidly during the deutonymphal instar. Only 2 inductive cycles of 10L:14D were required to induce up to 62% diapause if the mites were kept in continuous darkness during the remainder of their development. Long days or continuous light could reverse the inductive effect of a sequence of short-day cycles previously applied to the mites.Light breaks of 1 hr duration applied at different times during the dark period of a 10L:14D photoperiod generated a sharp bimodal response curve with two discrete points of sensitivity to the light breaks at 10 hr after ‘dusk’ and 10 hr before ‘dawn’, thus showing a remarkable similarity with the results obtained in light break experiments with some species of insects.     

In vivo and in vitro photoperiodic induction of diapause using isolated brain-suboesophageal ganglion complexes of the silkworm,Bombyx mori

By use of a bivoltine silkworm race which shows a long-day photoperiodic response after induction during the last (5th) instar, we tried to programme photoperiodic induction in the isolated brain-suboesophageal ganglion complex in vivo and in vitro. A pair of the complexes from a newly ecdysed 5th-instar female was transplanted into the abdomen of a late 5th-instar larva and exposed to long-day (20 h light: 4 h dark) or short-day (8 h light: 16 h dark) conditions for 3 cycles. The short-day-exposed complexes elicited the production of diapause eggs in the recipient silkworms destined to become non-diapause egg producers, whereas the long-day-exposed brain complexes produced non-diapause eggs. Transplant experiments of the brain-suboesophageal ganglion complex using isolated abdomens showed a similar result. The brain complexes from newly ecdysed females of the 5th-instar were cultured in Grace's insect medium under 20 h light: 4 h dark or 8 h light: 16 h dark for 4 cycles, respectively. After in vitro culture, a pair of complexes was implanted into the abdomen of a late 5th-instar larva destined to become a non-diapause egg producer, and the diapause incidence in the resultant moths was examined. The brain complexes which received the short-day cycles induced a large portion of diapause eggs, whereas those which received the long-day conditions induced non-diapause eggs. The connection of corpora cardiaca and corpora allata with the brain complex had no influence on the result. Suboesophageal ganglia which had been cultured in vitro and implanted elicited a remarkable production of diapause eggs, but cultured brains were ineffective in producing diapause eggs, regardless of the photoperiod experienced. These results demonstrate that photoperiodic induction of the silkworm can be programmed in in vivo and in vitro culture systems, and that components of the photoperiodic clock (photoreceptor, clock, and counter system) are located in the brain-suboesophageal ganglion complex, possibly in the brain itself.     

Endocrine events during pre-diapause and non-diapause larval-pupal development of the tobacco hornworm, Manduca sexta

The haemolymph ecdysteroid titre and in vitro capacities of prothoracic glands and corpora allata to synthesize ecdysone and juvenile hormone, respectively, during the last-larval instar of diapause-destined (short-day) and non-diapause-destined (long-day) Manduca sexta were investigated. In general, the ecdysteroid titres for both populations of larvae were the same and exhibited the two peaks characteristic of the haemolymph titre during this developmental stage in Manduca. The only difference in the titre occurred between day 7 plus 12 h and day 7 plus 20 h, when the short-day larval titre did not decrease as quickly as the long-day titre. The in vitro synthesis of ecdysone by prothoracic glands of short- and long-day larvae during the pharate pupal phase of the instar were also essentially the same. Activity fluctuated at times which would support the idea that ecdysone synthesis by the glands is a major contributing factor to the changes in the haemolymph ecdysteroid titre. There was one subtle difference in prothoracic gland activity between the two populations, occurring on day 7 plus 2 h. By day 7 plus 10 h, however, rates of ecdysone synthesis by the short- and long-day glands were comparable. This elevated activity of the short-day glands occurred just prior to the period the haemolymph ecdysteroid titre remained elevated in these larvae. The capacities of corpora allata to synthesize juvenile hormone I and III in vitro were not markedly different in long- and short-day last-instar larvae. At the time of prothoracicotropic hormone release in the early pupa, activity of corpora allata from short- and long-day reared animals was low and also essentially the same. There were a few differences in the levels of synthesis at isolated times, but they were not consistent for both homologues. Overall, there are no compelling differences in the fluctuations of ecdysteroids and juvenile hormones between diapause-destined and non-diapause-destined Manduca larvae. Since these hormones do not appear to play any obviously significant role in the induction of pupal diapause in this insect, the photoperiodic induction of diapause in Manduca appears to be a predominantly brain-centred phenomenon not involving endocrine effectors.     

Induction of diapause in the pupa of Phalaenoides glycinae by a hormone from the suboesophageal ganglion

The pupal diapause in Phalaenoides glycinae is facultative, and diapause is induced when larvae are reared in short days at low temperatures. By varying the stimulus and especially by changing larvae from one régime to the opposite during their development it is possible to induce diapause covering a wide and continuous spectrum of intensity. Wounding tends to intensify the diapause if it already exists no matter how weakly, but superficial wounding will not put a strongly non-diapausing individual into diapause. In P. glycinae diapause is caused by a hormone secreted by the suboesophageal ganglion. It is suggested that the intensity of the diapause depends on the concentration of the hormone and the duration of the period that the target (the neurosecretory cells of the brain) remains vulnerable. It is suggested that the suboesophageal ganglion may have the function of secreting a diapause-inducing hormone quite generally in short-day and long-day insects with facultative diapause and in species with obligate diapause as well.     

Geographic variation of diapause intensity in the spider mite Tetranychus urticae

Abstract. Eight strains of the spider mite Tetranychus urticae, originating from different localities in western and central Europe, with latitudes ranging from 40.5 to 60^oN, displayed marked differences in the period of chilling at 4^oC required for diapause termination under a diapause-maintaining short-day photoperiodic regime at 19^oC, to which the mites were transferred after the cold period. The higher the latitude from which the strains originated the longer was the period of chilling required for diapause termination, suggesting the presence of a gradient in diapause intensity, diapause being deeper the more northern the origin of the strains. Two strains originating from higher altitudes appeared to have a much deeper diapause than expected from their latitudinal origin. In addition, these two mountain strains showed mutual differences in diapause intensity, notwithstanding the fact that they originated from similar latitudes and altitudes; local climatic conditions probably act as strong selective forces with regard to diapause depth. All strains appeared to be sensitive to photoperiod during the period of diapause development. Diapause was quickly completed by a long-day photoperiod (LD 17:7 h), but was maintained by a short-day photoperiod (LD 10:14h). However, even under the latter regime sensitivity to photoperiod gradually diminished and eventually disappeared, thus leading to ‘spontaneous’ termination of diapause. The length of the period of diapause development, as measured by the sensitivity to photoperiod of diapausing mites, varied between strains; it was shorter in the southern strains and longer in the northern strains. The results indicate great variation in diapause intensity between strains, which is probably genetically determined and may have adaptive significance for this widespread species. When young females which had just entered diapause were kept for ever longer periods of time under the diapause inducing short-day regime at which they had been reared, before being transferred to the cold room, the duration of the period of chilling required for diapause termination was found to decrease proportionally in all three strains tested. These results suggest that intensification of diapause does not occur in T. urticae; diapause intensity seems to be highest at the beginning of diapause and to diminish gradually during diapause development.     

Artificial selection for responsiveness to photoperiodic change alters the response to stationary photoperiods in maternal induction of egg diapause in the rice leaf bug Trigonotylus caelestialium

Female adults of the rice leaf bug Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae) produce non-diapause eggs under long-day conditions, whereas they produce diapause eggs under short-day conditions. These egg-production modes change following a photoperiodic change from long-day to short-day conditions or vice versa, with individual variations in responsiveness shown in the time from the photoperiodic change to the mode change. Strains of this insect with higher or lower responsiveness to photoperiodic change were established after several generations of selection, indicating that the individual variation has a genetic basis. The selected strains that were more responsive and less responsive to one photoperiodic change were found to be less responsive and more responsive to the opposite photoperiodic change, respectively, indicating a significant negative correlation between responsiveness to reciprocal photoperiodic changes. The selected strains also had a significantly different incidence of diapause-egg producers in stationary photoperiods compared to a non-selected strain, showing that selections for responsiveness to photoperiodic change were essentially the same as selections for a higher or lower incidence of diapause-egg producers. These results indicate that responsiveness to photoperiodic change is one aspect of the tendency to produce diapause or non-diapause eggs.     

Relationship between photoperiod and secretion of the diapause hormone during larval stages of the silkworm, Bombyx mori L., reared on an artificial diet

The suboesophageal ganglion of the silkworm, Bombyx mori synthesizes sufficient diapause hormone to produce diapause eggs, regardless of the photoperiodic conditions experienced during the larval stages. When larvae destined to produce non-diapause eggs are implanted with the brain-suboesophageal ganglion complex from larvae which have been reared under short-day conditions, the resulting adults lay diapause eggs. The larvae receiving the complex from larvae reared under long-day conditions gave rise to adults which did not produce any diapause eggs. The brains from pupae which have been reared under long-day conditions show an activity inhibiting the secretion of diapause hormone by the suboesophageal ganglion. The mechanism through which the brain controls the secretion of diapause hormone from the suboesophageal ganglion can be modified by photoperiodic conditions during the larval stages.     

Effect of photoperiod and temperature on diapause in a Florida strain of the tropical warehouse moth Ephestia cautella

A photoperiodically-controlled diapause of the long-day, short-day type was identified in a brown-winged, yellow-eyed strain of Ephestia cautella (Walker). The proportion of larvae diapausing in very long photoperiods was less than in short photoperiods. The mean critical photoperiod, here defined as that photoperiod giving half the maximum percentage of insects that diapause in response to photoperiod at a given temperature, was between 12 and 13 hr for the long-day reaction at both 20 and 25°C. The principal sensitive phase occurred near the time of the last larval moult. The mean duration of diapause was 2–3 months at 20°C and slightly longer at 25°C. The optimum temperature for diapause development was near 15°C, all larvae pupating within 24 days after a 45-day exposure at this temperature. Diapause could be terminated whenever larvae diapausing at 20°C were exposed to as few as five long (15 hr) photoperiods at 25°C. Long photoperiods at 20°C, or short photoperiods (9 hr) at 25°C were less effective in terminating diapause.