Completion Of Diapause Research Articles

Development of the overwintering stages of the carrot fly, Psila rosae (Diptera: Psilidae)

AbstractThe overwintering stages of the carrot fly (Psila rosae (Fabricius)) were sampled at Wellesbourne, Warwickshire, during the winters of 1987, 1988, 1989 and 1990. Between 20% and 55% of the insects overwintered as pupae in diapause. The remaining insects stayed in the larval stage during the winter period and gave rise to non-diapausing pupae in the early spring. In May, adults emerged earlier, and over a shorter period, from insects that overwintered as larvae than those that overwintered as pupae. Diapause was most intense during late December and early January. In the laboratory, diapause was completed at temperatures of 5°C and above but was not completed at 0°C. When the overwintering stages were sampled in early February and maintained at constant temperatures in the laboratory, the overwintering pupae required from 114 days at 9°C to 44 days at 21.5°C to give rise to adults. In contrast, the overwintering larvae required only 91 days (9°C) and 27 days (21.5°C), respectively. Populations of overwintering P. rosae collected from Warwickshire and Norfolk had similar requirements for spring emergence but diapause pupae collected in Lancashire emerged over a longer period of time than those collected in Warwickshire. Comparisons with published data indicated that North American and European pupae had different requirements for the completion of diapause. Accumulation of weather data for a P. rosae forecast should start when temperatures are low and any date in early February would be suitable.

Effect of temperature on the termination of diapause in the univoltine almond seed wasp Eurytoma amygdali

AbstractDiapausing larvae of Eurytoma amygdali Enderlein (Hymenoptera, Eurytomidae) were collected in early August and late September. They were subjected to various photoperiod and temperature regimens for up to 20 weeks, then kept at L16:D8 and 19 °C for another 14 to 26 weeks for diapause to be terminated and pupation to take place.Photoperiod did not affect diapause completion. It was confirmed that the two morphologically distinct diapause stages have different temperature requirements for their completion. The first diapause stage was completed synchronously at temperatures between 16 and 19 °C. A higher temperature of 26 °C delayed diapause development. The second stage required lower temperatures between 4 and 10 °C. Spontaneous termination of diapause was observed at constant 19 °C.When applied to the first diapause stage for 20 weeks, low temperatures made the larvae refractory to subsequent intermediate temperatures. The first stage was thus maintained until a higher temperature of 26 °C made the larvae regain their ability to respond to the intermediate temperatures and complete this stage. Larvae grown in Retsou almonds had a higher diapause intensity than larvae grown in Truoito almonds.The results suggest that, in nature, the high temperatures of late summer and early autumn are likely to maintain the first diapause stage. Subsequently, the less warm temperatures of autumn allow the completion of the first stage by late autumn, and the low temperatures of late autumn and of winter allow the completion of the second diapause stage by mid winter.

Individual lake characteristics modify the life cycle and diapause habitat of two neighbouring populations of the cyclopoid copepod Thermocyclops oithonoides

Thermocyclops oithonoides (Cyclopoida, Copepoda) populations were studied in two neighbouring lakes with similar seasonal hydrographical characteristics. The two populations showed different life-cycle and diapause characteristics. The major differences were found in the number of generations per year (three versus two), the timing of induction and termination of diapause, temperature and oxygen conditions during diapause migration to the sediment, and habitat selection for wintering. Diapause initiation occurred at about 12 h light: 12 h dark in one population, but about 8 h L: 16 h D in the other. Higher habitat temperatures (approximately 5 °C) seemed to allow completion of a further generation in the warmest lake. The population descending early into the hypolimnion utilized the deep profundal sediment as a diapausing habitat. These specimens were most likely physiologically prepared for diapause, including tolerance to low-oxygen or anoxic conditions. The population with an additional generation, probably not yet in the complete diapause phase, avoided low-oxygen conditions and utilized mainly the oxygenated part of the profundal sediment as a diapausing habitat. The major part of both populations diapaused in the sediment, but a small fraction was in "active diapause" in the plankton during winter. In these populations of T. oithonoides, day length, modified by habitat temperature, seemed to influence diapause initiation, whereas habitat distribution during winter seemed to be influenced by the combined effect of diapause ontology and oxygen conditions in the potential wintering habitat.

Possible impact of global warming on cabbage root fly (Delia radicum) activity in the UK

SUMMARYA program for simulating the patterns of egg‐laying by populations of the cabbage root fly was used to model the effects of global warming on future cabbage root fly attacks.An increase of 3°C in mean daily temperature would cause the cabbage root fly to become active about a month earlier in the year than at present. Under such conditions, the emergence of flies from the overwintering population would be less synchronised, as the completion of diapause and post‐diapause development would occur at the same time in different individuals within the population. However, there would continue to be only three generations of fly each year, even in the south of England. With temperature increases of 5°C or 10°C, the fly would complete four generations each year and aestivation would seriously disrupt egg‐laying.These rises in temperature would have a major impact on cabbage root fly activity and would require new strategies for controlling this pest.

Effects of photoperiod, temperature, food and relative humidity on the induction of diapause in the predatory miteAmblyseius potentillae

Aspects of the induction of diapause were studied in a Dutch strain of the phytoseiid miteAmblyseius potentillae. The photoperiodic response curve was of the long-day type, with a sharply defined critical daylength of 14.5 h. Critical daylength varied only little at temperatures between 15.0 and 22.5°C. All post-embryonic and possibly even late-embryonic stages of development were found to be sensitive to photoperiod; sensitivity appeared to be maximal during the protonymphal stage. It is shown that β-carotene is necessary for some early step in the physiological mechanism of photoperiodic induction, and not (or not exclusively) for the expression of the diapause response. Two points of sensitivity to light could be demonstrated in the nights ofl∶d 13∶11 andl∶d 12∶12 long-night regimes, using 1-h night interruptions. These results are similar to those obtained in lightbreak experiments with spider mites and insects. However, no effect was found with light interruptions applied during the dark phase of anl∶d 10∶14 long-night regime. In resonance experiments with a constant photophase (12 h) and a variable scotophase, a weak rhythmic response was found at 22.5°C; at 19.0°C this effect was completely absent. The relative humidity experienced by the mites during diapause induction as well as during diapause development influenced the rate of diapause completion under long days (l∶d 16∶8). Diapause duration appeared to be shortest when the mites experienced low relative humidity (35±5%) during diapause induction and high relative humidity (75±5%) during diapause termination, and longest under the reverse conditions.

Dormancy in the Strawberry Leafroller (Lepidoptera: Tortricidae)

A 2-yr study of strawberry leafroller, Ancylis comptana (Froelich), populations in central Iowa showed that short daylengths and low temperatures maintain diapause during autumn and that this autumnal diapause ends without a specific cue by the end of December. The completion of diapause does not require chilling. The postdiapause developmental rate of A. comptana is linearly related to temperatures between 14 and 30°C; adult emergence requires 154 degree-days (DD) above a lower thermal threshold ( t ) of 10.5°C. Field cage studies demonstrated that 50% emergence of adult A. comptana from overwintering larvae can be predicted accurately based upon the accumulation of approximately 150 DD > 10°C.

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.

Multiple role of temperature during insect diapause: a review

AbstractThe review emphasizes that there are multiple pathways to diapause completion. The programmed course of events is modified by environmental cues. Often chilling is not a prerequisite for the completion of hibernation diapause (examples tabulated). Diapause completion progresses well at intermediate or high temperatures, sometimes it is even stimulated by high or increasing temperature. Low temperatures are important, as they (1) conserve metabolic reserves, (2) prevent resumption of post‐diapause morphogenesis and thus synchronize the life‐cycle, (3) represent contrast to the later increase in temperature. Diapause consists of phases with different prerequisites. There is a principal difference between diapause development and photoperiodic activation as indicated by the subsequent physiological condition of insects.

Diapause Termination and Postdiapause Development in Eggs of Hydraecia immanis Guenée (Lepidoptera: Noctuidae)

Most diapause eggs of Hydraecia immanis Guenée stored in environmental chambers at 1.7 and 4.4°C terminated diapause after ca. 2 or 3 mo. After diapause was completed, mean egg hatch occurred in ca. 12 or 13 d at 21.1°C. About 0.1% of eggs held continuously at 21.1°C hatched without exposure to cold storage, which indicates that low temperatures are not required to terminate diapause for all eggs. Diapause eggs laid between 16 August and 4 September 1985 in a greenhouse under conditions of natural daylight and placed in an outdoor weather shelter in Champaign, Ill., on 4 September, generally terminated diapause by the end of the year, although some eggs did not complete diapause until later in winter. To achieve 50% hatch under field conditions, 119.5 degree days above a threshold temperature of 9.43°C were required by eggs that had completed diapause.

Increased cold hardiness in eggs of Arcynopteryx compacta (Plecoptera) by dehydration

Eggs of the stonefly, Arcynopteryx compacta, that overwinter in the alpine region of Norwegian mountains, increase their cold-hardiness by dehydration. Eggs enclosed in ice at −22°C survive the loss of about two-thirds of their total water content by shrinkage due to passive diffusion of body water along the concentration gradient. Fully hydrated eggs are killed by freezing at their supercooling point of −26°C, and by direct cooling to −30°C. Dehydrated eggs have a mean supercooling point of −31°C, and survive exposure at −27 and −29°C in ice. Judged from their melting points the eggs do not accumulate low-molecular-weight cryoprotective substances. The difference between freezing and melting points corresponds to a thermal hysteresis of up to 1.8°C. The presence of thermal hysteresis antifreezes may stabilize their supercooled state when enclosed by ice during overwintering. The eggs enter diapause in the autumn, and diapause completion is enhanced both by temperature and time during enclosure in ice.

Diapause development and photoperiodic activation in starving females of Pyrrhocoris apterus (Heteroptera)

Diapausing adults of Pyrrhocoris apterus 3–9 weeks old were exposed for 1–10 weeks to combinations of photoperiod (18L:6D; 12L:12D) and temperature (26°C, 15°C) under starvation. Their response was then measured by the incidence of oviposition and duration of oviposition delay after a switch to 18L:6D, 26°C and feeding. Since vitellogenesis is prevented in starving females, diapause completion was reliably separated from post-diapause morphogenesis. Tachytelic processes of photoperiodic activation did not require feeding, but high temperature was essential; at 15°C and 18L:6D only horotelic completion of diapause (i.e. diapause development) was possible, similarly to 12L:12D and 26°C or 15°C. Tachytelic processes were even stimulated by starvation. Starvation did not increase the rate of horotelic processes. Tachytelic completion of diapause did not result in the loss of photoperiodic response. The involvement of changes in the photoperiodic clock in the horotelic and tachytelic processes is discussed.

Adult Reproductive Diapause in the Mexican Bean Beetle (Coleoptera: Coccinellidae): Interaction of Temperature with Photoperiod

Survivorship and cumulative oviposition patterns were determined for cohorts of summer generation and overwintered Mexican bean beetle adults, Epilachna varivestis Mulsant, at a series of constant and alternating (12 h:12 h) temperature regimes. All photoperiods were LD 12:12, with the low temperature portion of each alternating regime occurring during the dark period. Overwintered adults showed no indication of prolonged survivorship or delayed oviposition suggestive of diapause and may represent postdiapause individuals. All summer generation adults at 25°C, 30:20°C, and 30°C oviposited, died, or both during the first 100 days of incubation and may represent nondiapause individuals. At both 15 and 20°C, about 25% of each cohort exhibited prolonged survivorship (to day 327), delayed oviposition (after day 160), or both. These individuals resumed feeding significantly earlier at 20 than 15°C, suggesting faster completion of diapause and commencement of postdiapause activity at the higher temperature. At 20°C, adults apparently entered and completed diapause and then completed postdiapause oviposition.

Studies on some effects of relative humidity, food and light in termination of larval diapause in Busseola fusca (Lepidoptera: Noctuidae)

Time required in the laboratory for field collected Busseola fusca Fuller larvae to complete diapause development and to pupate decreased as the dry season progressed. Low relative humidity, darkness and the absence of food retarded diapause development as compared to (he opposing factors. However, the completion of diapause development and pupation did not occur solely because a particular threshold of any of the factors was exceeded, but rather, because of the cumulative effects of time and anyone of, or all the factors tested.

Environmental Control of the Seasonal Life Cycle of Adalia bipunctata (Coleoptera: Coccinellidae)

Adalia bipunctata L. has low developmental thresholds ( t ) for postdiapause and nondiapause development that adapt it to activity early in the season. Postdiapause reproductive development leading to oviposition requires an accumulation of 87 degree-days ( K ) above a relatively low developmental threshold temperature ( t ) of 6.8°C. Overwintering adults disperse and initiate oviposition during early to mid-May. The linearly derived ( t ) and ( K ) values of 263 ± 9.0 degree-days above 9.0°C for preimaginal development and daily maximum-minimum temperatures from outdoors accurately predicted outdoor developmental rates. Preimaginal development outdoors during June and July required 269 ± 12 degree-days above 9.0°C under conditions of excess prey. In the field, there are two to three generations per year in the Ithaca, N.Y., area. The critical photoperiod for diapause induction in the Ithaca, N.Y., (~42°N) population lies between LD 13:11 and LD 14:10 (23°C). Short daylengths maintain diapause, and during autumn the duration of diapause is quantitatively related to photoperiod. Diapause completion does not require chilling: during winter-early spring. photoperiod may exert some influence on the timing of diapause termination.

The regulation of development during diapause in Ephestia elutella (Hübner) by temperature and photoperiod

Diapausing larvae of Ephestia elutella reared at 20°C in short photoperiods (LD 11:13), and then maintained 12 weeks or longer at 5–15°C before transfer to 20 or 25°C, pupated sooner than unchilled controls. At 25°C, all samples kept in long photoperiods (LD 15:9) survived better and pupated faster than similarly treated samples held in short photoperiods (LD 9:15). Samples kept at 20°C after chilling pupated much slower than those at 25°C, and, except after exposure at 5°C, pupated at similar rates at LD 11:13 or 15:9, although mortality was higher at the shorter photoperiod. After exposure at 5°C, larvae required increased day-length as well as increased temperature to hasten pupation whereas after exposure at 10°C most responded to increased temperature only. For samples maintained in slightly heated or unheated outbuildings, the summer emergence was poorly synchronized and males on average emerged ahead of females. Samples moved from the unheated outbuilding to 25°C and long days in the laboratory in early spring, however, pupated quickly and males and females emerged together. A late phase of diapause development thus exists requiring both high temperature and long photoperiods to ensure a prompt resumption of morphogenesis. Spring temperatures in the United Kingdom are seldom high enough to synchronize the completion of diapause.

Intermittent character of adult diapause in Aelia acuminata (Heteroptera)

The response to photoperiod of field-collected Aelia acuminata was studied by exposing insects to three photoperiodic regimes. After the completion of diapause the insects do not respond to photoperiod: in mid-February the length of the pre-oviposition period is the same under both long and short photoperiods. After the onset of oviposition, insects again become responsive to photoperiod regardless of the time of year: under long day, oviposition lasts until death, whereas under short day the females cease oviposition after about 3 weeks. After a further 2 or 3 months without ovipositing, these females which are still experiencing short-day conditions resume reproduction for a further 4–7 weeks and long-lived individuals have three oviposition periods. A regulatory mechanism is suggested for the alternation between oviposition and diapause.

FACTORS AFFECTING DIAPAUSE DEVELOPMENT AND SURVIVAL IN THE PUPA OF MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

AbstractOnly soil temperatures below −7°C are likely to cause significant pupal mortality of M. configurata in the field, and only if exposure periods are sufficiently prolonged. At −17°C, a temperature not uncommonly encountered in the soil at 10 cm during the prairie winter, near total mortality occurred within 1 week in laboratory tests and significant mortality (20–30%) occurred within 1 day. The survival time at −12°C was considerably longer, and 50% mortality occurred after about 6 weeks of exposure. Pupal mortality caused by cold might thus vary from 0 to 100% depending on local climatic and field conditions and therefore is an essential component of a survival model for the species.Exposure to cold accelerates diapause development by as much as four orders of magnitude for the lowest temperature tested (−17°C). However, the acceleration of diapause development by sub-zero temperatures appears to be of limited phenological significance, since in western Canada the pupae spend at least 40 weeks in the soil and can easily complete diapause development within this time at 0° to 5°C. Further evidence for a major reorganization of the endocrine system of M. configurata pupae during stage 2 of diapause development is presented.

Diapause completion time of pear leaf miner

Diapause completion time of pear leaf miner

The common nemobiine field crickets of New Zealand (Orthoptera : Gryllidae)

Abstract Two new species of nemobiine crickets, Pteronemobius nigrovus and Pteronemobius bigelowi, are described. Both are widely distributed in grasslands throughout New Zealand and are sympatric in many areas. P. nigrovus eggs from Christchurch required 5–8 weeks at 5–9°C to complete diapause while P. bigelowi eggs from Kaikoura required 8–10 weeks at 5–9°C. Diapause in the eggs of both species occurs before a visible embryo is formed. Crosses between P. nigrovus from Christchurch and P. bigelowi from Kaikoura indicate that a high degree of reproductive isolation exists.

Bioclimatic Studies of the Aphid Parasite Praon exsoletum.1 2. Thermal Limits to Development and Effects of Temperature on Rate of Development and Occurrence of Diapause

Using bioclimatic chambers, fluctuating temperatures and humidities were examined for their effects on the development of the immature stages of Praon exsoletum (Nees) (Hymenoptera: Aphidiidae), a parasite of the spotted alfalfa aphid, Therioaphis trifolii (Monell) (= T. maculata (Buckton)) (Homoptera: Aphididae). Comparisons with response of the host to the same temperature conditions were made. The thermal limits for development of the parasite are diurnal means of 10 and 27°C, and development is fastest at 23°C. The host develops over a wider range, namely 6–32°C, and most rapidly at 26°C. At any temperature level the host grows more rapidly, and at 26°C it completes development in 6 days in contrast to the IS days required by the parasite. Diapause is induced in the parasite by low temperatures, beginning at diurnal means of 16°C and less, but it can be suppressed by long photoperiods (14 hrs or more). The host does not enter diapause under these same conditions. The age of the female parasite does not affect the incidence of diapause of her progeny, nor do the growing conditions of the host plants. Cool fluctuating temperatures accelerate parasite development relative to that occurring in constant-temperature conditions, and they also permit development to occur at thermal levels well below the constant-temperature threshold. On the other hand, high fluctuating temperatures are injurious to the parasite. The parasite can develop only over a restricted range of medial temperatures and to that extent can be rated a mesotherm, in contrast to the eurythermic host. Typical winter conditions in the Central Valley of California were simulated in a bioclimatic chamber and were found not injurious to the parasite. Instead it was found able to complete diapause and emerge as an adult in midwinter at a monthly mean temperature of 8°C.