Post-diapause Period Research Articles

Temperature-Dependent Development of the Post-Diapause Periods of the Apricot Seed Wasp Eurytoma maslovskii (Hymenoptera: Eurytomidae): An Implication for Spring Emergence Prediction Models.

Simple SummaryEurytoma maslovskii is an important stone fruit pest whose control relies on application timing, which requires a reliable tool for predicting spring emergence. The most common approach in insect phenological modeling is based on temperature-dependent development and thermal bioparameters. However, not a lot is known regarding E. maslovskii. In the present study, we investigate the development of E. maslovskii after diapause breaks at various temperatures. The lower temperature threshold and thermal constant of the species after diapause are estimated. The results confirm that the field emergence of E. maslovskii can be predicted by a model using accumulated degree days starting from 1 January, thereby providing an efficient tool for pest-control decision making.The present study investigates the influence of temperature on the development of Eurytoma maslovskii after a diapause break up until adulthood. The insect development rate was fitted to both linear and nonlinear models to estimate thermal bioparameters, which served as the basis for constructing prediction models. Chilled apricot seeds collected in November were used for the experiments in March. Experiment 1 used intact seeds, while experiment 2 used overwintered larvae obtained by cracking the endocarp cover. Both larvae and intact seeds were subjected to seven constant temperatures (14.5, 18.8, 21.3, 24.0, 27.0, 30.2, and 34.3 °C). The post-diapause larvae of E. maslovskii developed into adults at a temperature range of 14.5–30.2 °C, and no larvae pupated at 34.3 °C. The lower temperature thresholds (LTs) for post-diapause larva and pupa and the total post-diapause period until adult emergence and until adult exit were 8.1, 8.2, 8.2, and 7.3 °C, respectively, whose thermal constants (DD) were 66.2, 180.2, 246.9, and 336.7 degree days, respectively. The distribution of E. maslovskii at all post-diapause stages was described using a two-parameter Weibull function. The data predicted by the model using accumulated degree days starting from January 1 did not differ by more than three days from the observed field emergence of E. maslovskii. Our data provide insights into the development of E. maslovskii after diapause. Temperature-dependent development supports the use of a degree day model to predict field emergence for pest timing control.

Nesting Biology and Offspring Development of the Cavity-Nesting Solitary Wasp Isodontia elegans (F. Smith) from Trap-Nests in Oregon

We studied the nesting biology and developmental schedules of the cavity-nesting solitary wasp Isodontia elegans in Oregon, USA. Trap-nests contained 1–15 brood cells each, separated by partitions, which adult females made with grass fragments. Before leaving nests to hunt, females made loose, temporary closures of longer fragments of dried grass and, upon returning, briefly deposited prey just inside the nest entrance before transferring them to a cell. Cells were provisioned with katydids (Meconema thalassinum, an invasive species in North America) and tree crickets (Oecanthus fultoni), the latter predominating as summers progressed. The inner cells of nests, where most daughters developed, were longer and separated from adjacent cells by partitions thicker than those in outer cells, where most sons developed. These observations, along with the fact that daughters are larger than sons (likely because they receive a greater provision mass from mothers), indicate that investment in daughters is considerably greater than that in sons, by multiple measures. Sexual size dimorphism was evident in both cocoon mass (prepupae + cocoon case) and adult mass. From 2013 to 2019, nesting began earlier in the summer when mean maximum daily temperatures in June were higher and when the number of days in June with maximum temperatures <25 °C were fewer. Once nesting began, females typically completed 1 cell per day, the egg being laid on one of the first 3 prey placed in the cell. In the field, eggs hatched in 2–6 d, and larvae completed feeding and began cocoon spinning 5–11 d later. After removal from winter storage, offspring completing development at 29 °C emerged as adults in 22–40 d, with males emerging about 2 d earlier on average. The duration of the postdiapause period leading to adult emergence, however, was not correlated with eventual adult mass in either sex. We discuss interpopulation differences in prey species and nest materials used by I. elegans.

Modelling diapause in mosquito population growth.

Diapause, a period of arrested development caused by adverse environmental conditions, serves as a key survival mechanism for insects and other invertebrate organisms in temperate and subtropical areas. In this paper, a novel modelling framework, motivated by mosquito species, is proposed to investigate the effects of diapause on seasonal population growth, where the diapause period is taken as an independent growth process, during which the population dynamics are completely different from that in the normal developmental and post-diapause periods. More specifically, the annual growth period is divided into three intervals, and the population dynamics during each interval are described by different sets of equations. We formulate two models of delay differential equations (DDE) to explicitly describe mosquito population growth with a single diapausing stage, either immature or adult. These two models can be further unified into one DDE model, on which the well-posedness of the solutions and the global stability of the trivial and positive periodic solutions in terms of an index [Formula: see text] are analysed. The seasonal population abundances of two temperate mosquito species with different diapausing stages are simulated to identify the essential role on population persistence that diapause plays and predict that killing mosquitoes during the diapause period can lower but fail to prevent the occurrence of peak abundance in the following season. Instead, culling mosquitoes during the normal growth period is much more efficient to decrease the outbreak size. Our modelling framework may shed light on the diapause-induced variations in spatiotemporal distributions of different mosquito species.

Diet and nutritional status during early adult life have immediate and persistent effects on queen bumble bees.

Many insects sequester nutrients during developmentally programmed periods, which they metabolize during subsequent life history stages. During these periods, failure to store adequate nutrients can have persistent effects on fitness. Here, we examined a critical but under-studied nutrient storage period in queen bumble bees: the first days of adult life, which are followed by a diapause period typically coinciding with winter. We experimentally manipulated availability of pollen (the primary dietary source of lipids and protein) and the sugar concentration of artificial nectar (the primary source of carbohydrates) for laboratory-reared queens during this period and examined three nutritional phenomena: (i) diet impacts on nutritional status, (ii) the timescale upon which nutrient sequestration occurs and (iii) the fitness consequences of nutrient sequestration, specifically related to survival across the life cycle. We found evidence that pollen and nectar starvation negatively impact lipid storage, whereas nectar sugar concentration impacts stored carbohydrates. The majority of nutrients were stored during the first ~ 3days of adult life. Nutrients derived from pollen during this period appear to be more critical for surviving earlier life stages, whereas nutrients sequestered from nectar become more important for surviving the diapause and post-diapause periods. Negative impacts of a poor diet during early life persisted in our experiment, even when pollen and a relatively high (50%) nectar sugar concentration were provided post-diapause. Based on these findings, we posit that the nutritional environment during the early adult life of queens has both immediate and persistent impacts on fitness. These findings underscore the importance of examining effects of stage-specific nutritional limitations on physiology and life history traits in this social insect group. Moreover, the findings may shed light on how declining food resources are contributing to the decline of wild bumble bee populations.

Expression profiles of 14 small heat shock protein (sHSP) transcripts during larval diapause and under thermal stress in the spruce budworm, Choristoneura fumiferana (L.).

Diapause is an important strategy for certain insect species to survive unfavorable environmental conditions, including low temperatures experienced when they overwinter in cold climate. Many studies have indicated that the increased expression of heat shock proteins during diapause improves the thermal tolerance of insects. However, the relationship between small heat shock proteins (sHSPs) and diapause is not clear or well-researched. In this study, we investigated the transcript levels of 14 sHSP genes in the spruce budworm, Choristoneura fumiferana, a major pest of spruce and fir in Canada, during pre-diapause, diapause, and post-diapause under normal rearing conditions and in response to a heat shock treatment. We found that sHSP expression profiles could be classified into five patterns under normal laboratory conditions: pattern I was upregulated only during pre-diapause, pattern II was upregulated only during diapause, pattern III was constantly expressed throughout diapause, pattern IV was upregulated in both pre-diapause and diapause, and pattern V was upregulated only during post-diapause. After heat shock, five different expression patterns were observed: pattern I responded weakly or not at all throughout diapause, pattern II responded weakly during the diapause stage but strongly at the onset of diapause and in the post-diapause period, pattern III was upregulated only during post-diapause, pattern IV was strongest during diapause, and pattern V was strongest only in early diapause. These complex expression profiles lead us to suggest that most of the sHSP genes are involved in the diapause process and that they may have multiple and important roles in different phases of this process.

Mechanisms underlying spruce budworm outbreak processes as elucidated by a 14‐year study in New Brunswick, Canada

AbstractWe conducted a 14‐yr intensive study of spruce budworm (Choristoneura fumiferana (Clem.)) survivorship at three study plots in largely balsam fir (Abies balsamea (L.) Mill.) stands in New Brunswick, Canada, to elucidate certain key mechanisms underlying spruce budworm outbreak cycles. The study covered a peak‐to‐declining phase (from 1981 and 1994) of the budworm outbreak cycle that had started in the early 1960s. Frequent sampling was carried out in each plot‐year to construct a practically continuous survivorship curve, and the annual variation in population density was estimated. We found a high level of correlation between the studied phase of the outbreak cycle and annual variations in the survivorship over the postdiapause period, suggesting that postdiapause survivorship was the chief determinant of the cycle. We found the annual changes in population density in the present study to be closely similar in pattern to those from the provincial budworm surveys conducted in much larger areas. This implies that the mechanism underlying the population process found in the few study plots in largely balsam fir stands also applies to the process in much larger areas of diverse stand types. The main source of postdiapause mortality is found to be natural enemies. The impacts of parasitoids and disease are evaluated by rearing budworm samples in the laboratory. Hymenopteran and dipteran parasitoids are by far the major sources of mortality, and microsporidians are the most prevalent pathogen. Occurrences of other entomopathogenic fungi and viruses were insignificant throughout the study. Seasonal changes in laboratory survivorship are compared with the corresponding field survivorship to estimate the effect of predation. No major mortality factor is found to singly play a predominant role in determining the outbreak cycle. Conversely, some minor factors are shown to have played significant roles. Thus, the importance of recognizing the action of natural enemies as a complex is emphasized for understanding the budworm outbreak cycle. Finally, centered on the roles played by the chronological succession of natural enemies in the present study, the results of budworm research in New Brunswick since the mid‐1940s are synthesized to outline basic mechanisms underlying the outbreak processes as a guide for further studies.

Egg laying behaviour, host plants and larval survival of Euphydryas aurinia provincialis (Lepidoptera Nymphalidae) in a Mediterranean population (central Italy)

In this paper, we show the results of research that can inform conservation measures elsewhere in Europe for the endangered butterfly Euphydryas aurinia. A five year field study was undertaken to identify the host plant preference of larvae of Euphydryas aurinia provincialis in the Mediterranean and which signals are used by females to lay their eggs. The females oviposit on Gentiana cruciata, Scabiosa columbaria and Cephalaria leucantha; the larvae feed on all these plants and additionally on Lonicera caprifoliumin the wild and on Gentiana lutea in the laboratory. The females do not show any preference for a specific host plant and the larvae move from one species of plant to another without any difficulty. The most important factors in determining the female oviposition are the visibility, accessibility and sun-exposure of the host plants. The vegetative state of host plants is the key factor in larval use of plants during the pre- and post-diapause period. The large-sized host plants, G. cruciata and C. leucantha, are optimal for the growth and survival of the pre-diapause I-III larval instar, while they are unavailable to the larvae in Spring because of their delayed vegetative growth. The post-diapause larvae preferentially feed on plants of S. columbaria, and to lesser degree L. caprifolium, as they provide and abundant food source compared with G. cruciata and C. leucantha. The results also suggest that, there is an evolutionary advantage in large numbers of caterpillars feeding together, with the females of E. aurinia provincialis preferring to lay their eggs nearby or above egg batches laid previously by another female, and selecting large plants for oviposition. Despite the competition for food among caterpillars, the oviposition behaviour of females is advantageous and increases the larval survival rate on large plants. The gregarious larval behaviour provides several benefits during both pre-diapause period (avoiding starvation) and post-diapause period (efficiency in thermoregulation).

Lipids and fatty acids in Calanus sinicus during oversummering in the southern Yellow Sea

Over-summering is a crucial period for Calanus sinicus in the southern Yellow Sea, where it is a key member of the zooplankton community. Lipids play an important role in copepod diapause, which is part of their over-summering strategy. We investigated how different fatty acids and lipid classes, including wax esters, changed during over-summering of C. sinicus during three cruises in June and August 2011 and November 2010, corresponding to the pre-, during and post-diapause periods, respectively. Large amounts of lipids were accumulated, mainly wax esters as previously found in C. finmarchicus during its diapause, and most of the storage lipids were used during over-summering. Wax ester polyunsaturated fatty acids (PUFAs) showed the most variation of the fatty acids (FAs), while the percentage composition of FAs in polar lipids was relatively stable. Selective use of wax ester PUFAs has already been shown to play important roles in the winter diapause of Calanus species in other regions, and our FA results show that this is the case for the Yellow Sea Cold Bottom Water (YSCBW) population that diapauses in summer.

The Potential Roles of the G1LEA and G3LEA Proteins in Early Embryo Development and in Response to Low Temperature and High Salinity in Artemia sinica.

Late embryogenesis abundant proteins (LEA) are stress resistance-related proteins that play crucial roles in protecting against desiccation, cold and high salinity in a variety of animals and plants. However, the expression pattern, distribution and functions of LEA proteins in the post-diapause period of Artemia sinica, and under high salinity and low temperature stresses, remain unknown. In this study, the complete cDNA sequences of the group 1 LEA (As-g1lea) and group 3 LEA (As-g3lea) genes from A. sinica were cloned. The expression patterns and location of As-G1LEA and As-G1LEA were investigated. The protein abundances of As-G1LEA, As-G3LEA and Trehalase were analyzed during different developmental stages of the embryo and under low temperature and high salinity stresses in A. sinica. The full-length cDNA of As-g1lea was 960 bp, encoding a 182 amino acid protein, and As-g3lea was 2089 bp, encoding a 364 amino acid protein. As-g1lea and As-g3lea showed their highest expressions at 0 h of embryonic development and both showed higher relative expression in embryonic, rather than adult, development stages. The abundances of As-G1LEA, As-G3LEA and trehalose were upregulated under low temperature and downregulated under high salinity stress. These two genes did not show any tissue or organ specific expression. Our results suggested that these LEA proteins might play a pivotal role in stress tolerance in A. sinica

Emergence of the overwintering generation of peach fruit moth (Carposina sasakii) depends on diapause and spring soil temperatures

Survival rate and emergence timing of the overwintering generation of many temperate agricultural pests is expected to affect their population dynamics and damage potential. However the impact of fluctuating winter and spring conditions on the successful emergence of insects post-diapause is generally poorly known. Here we characterize diapause responses in the peach fruit moth (PFM) pest, Carposina sasakii Matsumura, which overwinters at the larval stage in soil. Temperatures at a depth of 5cm fluctuated markedly in early spring during the critical PFM post-diapause period (late December to mid-April). By removing outdoor larval samples over this period, we show that the completion of diapause for PFM in northern China starts from late January and continues until March. This extended developmental period is accompanied by an ongoing loss of cold resistance. Temperature conditions experienced in the field were associated with cold tolerance and emergence times, and reduced cold tolerance was associated with shorter emergence time. Cryoprotectants declined from late December, and levels were associated with changes in the supercooling point (SCP) of the larvae, but both correlated weakly to survival under cold stress during the post-diapause period. These findings suggest that diapause stage and soil temperatures should be taken into account when predicting field dynamics of soil-dwelling overwintering insects based on degree day accumulation models and other approaches.

Expression and roles of As-NUPR1 protein from Artemia sinica during embryo development and in response to salinity stress

As-NUPR1, a stress-related protein, plays an important role in post-diapause during embryonic development in the brine shrimp Artemia sinica. In the present study, successful expression of As-NUPR1 from the cDNA sequence isolated from A. sinica was demonstrated using a prokaryotic expression system. The recombinant protein consisted of 132 amino acids with a molecular weight of 15kDa, and a predicted isoelectric point of 7.17. As-NUPR1 polyclonal antibodies were prepared by immunization of Balb/c mice with purified recombinant As-NUPR1 protein as an antigen, and immunological studies were carried out. Expression of As-NUPR1 during different developmental stages of the embryo and in response to salinity stress was analyzed in A. sinica using Western blots. The experimental results showed that the expression of As-NUPR1 is widely distributed at different developmental stages in A. sinica, and there was no tissue or organ specificity. Expression of As-NUPR1 decreased gradually during the diapause termination stage of embryo development, after which there was a general increase in expression after breaking the shell. In addition, As-NUPR1 expression was highly upregulated under conditions of high salinity. These results suggest that the As-NUPR1 protein is a stress-related protein that plays a role in protecting embryos from high salt damage in different embryonic developmental stages, especially during the post-diapause period.

Study of intracellular localization of the proteolytic enzyme complex and its protein inhibitors in bombyx grain

Intracellular localization of serine, cysteine and aspartate proteases, as well as their protein inhibitors, in bombyx grain in the postdiapause period of embryogenesis has been studied. Proteolytic activity of aspartate and cysteine proteases was found in lysosomal, mitochondrial, and nuclear fractions of grains. Serine protease activity was not observed in subcellular fractions of grains of the fourth day of postdiapause development. It has been shown that activities of protein inhibitors and certain peptide hydrolases in subcellular fractions provide consistent functioning and fine regulation of the proteolytic enzyme complex.

Temperature effects on embryonic development of Paratlanticus ussuriensis (Orthoptera: Tettigoniidae) in relation to its prolonged diapause

Paratlanticus ussuriensis eggs overwinter by entering diapause, which can be prolonged to more than 1 year depending on environmental conditions. To determine temperature effects on diapause duration of P. ussuriensis eggs, the rates of embryonic development and hatching were compared at various temperatures conditions by measuring embryonic stages and egg weights. Most eggs stayed in a very young stage (blastoderm formation, stage 4) when reared at 15 and 20 °C, 10–30% eggs developed into middle or late stages when reared at 25 °C, and most embryos developed fully (stage 23/24) when reared at 30 °C. Egg weight at 30 °C was 1.5 times higher than those reared at 20 °C. Chilling induced hatching in embryos at stage 23/24. Chilling caused stage 4 embryos to develop into stage 24, but they failed to hatch in response to a second warm period. Thus, P. ussuriensis eggs can overwinter either as young embryos (initial diapause) or as fully-developed embryos (final diapause). Eggs that experience an initial diapause overwinter again the second year in a final stage diapause. The post-diapause period was shorter when embryos overwintered in a final stage diapause. The hatching rate was highest in a temperature range of 7.5–15 °C. Our results suggest that temperature is an important environmental factor for the control of prolonged diapause in P. ussuriensis and initial diapause plays an important role in the control of its life cycle.

Sexual differences in diapause induction of the cotton bollworm, Helicoverpa armigera (Hb.)(Lepidoptera: Noctuidae).

The induction and termination of pupal diapause of Helicoverpa armigera were examined in three local populations from Kagoshima, Okayama and Ishikawa in Japan. Pupae in diapause retained eyespots for much longer than non-diapause pupae, and for markedly diverse durations. Once eyespots disappeared at the end of diapause, the period required for development until eclosion was more or less constant at 18°C. In all experiments repeated twice under the same conditions, male pupae generally showed a high tendency to enter diapause while female pupae showed a slight and rather population-specific tendency towards diapause. This trait as well as the higher intensity of male pupal diapause and the shorter post-diapause period of females suggest that females emerge first in the field in spring. This feature was regarded to be potentially important for considering the life-history strategy of this cosmopolitan pest.

DNA synthesis by testicular follicles in a lady-beetle, Coccinella septempunctata brucki (Coleoptera: Coccinellidae) in relation to aestivation diapause

Summary The present study confirmed that imaginal aestivation diapause in the seven-spotted lady-beetle, Coccinella septempunctata brucki, was characterized by the arrested reproduction not only in females (Okuda and Chinzei, 1988) but also in males. Changes in spermatogenesis by the testicular follicles and development of the male accessory gland were observed during prediapause, diapause and the post-diapause period. DNA synthesis by testicular follicles was examined as a criterion to assess spermatogenesis. DNA synthesis in the testicular follicles from pre-diapause male adults was as active as that from post-diapause ones. DNA synthesis gradually decreased with the induction of diapause and reached minimum activity on day 30 after emergence. Later DNA synthesis gradually resumed and reached its maximum activity when the male adults completed diapause on day 120. The male accessory glands developed intermediately during the pre-diapause period based on total protein content, which showed its minimum value in the middle of diapause and regeneration occurred with the termination of diapause. Methoprene treatment to diapausing male adults induced reproductive activation, i.e., increases of DNA synthesis by the testicular follicles and protein content of the male accessory glands. In contrast to the in vivo results, 5-h incubation of testicular follicles from diapausing males in Grace's medium containing methoprene induced no significant elevation of DNA synthesis. Histological study suggested an occurrence of a diapause-specific lipid in the testicular follicles, and this was confirmed by thin layer chromatography analysis.

Activity of gut alkaline phosphatase, proteases and esterase in relation to diapause of pharate first instar larvae of the gypsy moth,Lymantria dispar

Two distinctly different patterns of gut enzyme activity were noted in relation to diapause in pharate first instar larvae of the gypsy moth, Lymantria dispar. Trypsin, chymotrypsin, elastase, aminopeptidase and esterase activities were low at the initiation of diapause and through the period of chilling needed to terminate diapause. At the completion of a 150 day chilling period, activity of each of these enzymes quickly increased when the pharate larvae were transferred to 25°C. By contrast, activity of alkaline phosphatase (ALP) increased rapidly at the onset of diapause, remained elevated throughout diapause, increased again during postdiapause, and then dropped at the time of hatching. In addition, zymogram patterns of ALP activity differed qualitatively in relation to diapause: several bands were detectable during the pre- and postdiapause periods, but only one band, a band of high mobility, was visible during diapause. The ALP isozyme present in diapausing pharate larvae had a pH optimum of 10.6. Diapause in the gypsy moth can be averted by application of an imidazole derivative, KK-42, and pharate larvae treated with KK-42 showed elevated protease and esterase activity, low ALP activity, and expressed ALP isozymes with low mobility. Thus the overall patterns of gut enzyme activity and the ALP zymogram in KK-42 treated individuals were similar to those observed in untreated individuals at the termination of diapause. Our results suggest a unique pattern of enzyme activity in the gut that is regulated by the diapause program. Arch. Insect Biochem. Physiol. 37:197–205, 1998. © 1998 Wiley-Liss, Inc.

Dormancy in Lymantria dispar (Lepidoptera: Lymantriidae): Analysis of Photoperiodic and Thermal Responses

Dormancy in the gypsy moth is a dynamic process characterized by complex and seasonally variable responses to physical factors. At the end of summer and the beginning of autumn, short daylengths play a small, but perceptible role in diapause maintenance in a small proportion of individuals. By comparison, temperature has a much larger role in diapause maintenance and in the timing of postdiapause hatching. Temperatures >;15.6°C decelerate diapause development, and thus maintain diapause, whereas exposure to 5.0 or 10.0°C accelerates diapause development and enhances the incidence, speed, and synchrony of hatching under warm conditions. A small proportion of individuals in some egg masses need not experience low temperature before they hatch; these individuals hatch in the fall. The thermal responses of the larvae within the eggs change as they undergo dormancy in nature; these changes are evident in the temperature-developmental response curves, the lower thermal thresholds and heat units required for hatching, and the relative rates of development under a range of temperatures. The pattern of change in the thermal responses throughout dormancy suggests that as autumn and winter proceed, there is a gradual transition from diapause to postdiapause periods of dormancy. Thermal responses during dormancy vary considerably among egg masses.

Vitellogenesis in a lady-beetle, Coccinella septempunctata in relation to the aestivation-diapause

Yolk-protein precursor, vitellogenin, synthesis and effects of juvenile hormone analogue on vitellogenesis were studied in a lady-beetle, Coccinella septempunctata, which enters aestivation-diapause in the adult stage. In the prediapause period, total protein synthesis in the fat body was relatively high but vitellogenin synthesis was negligible. During diapause, total protein synthesis declined to a low level (but detectable) and vitellogenin synthesis was not detected at all. In the course of diapause termination, total protein synthesis recovered gradually, but vitellogenin synthesis did not occur before feeding. Juvenile hormone analogue application to a diapausing female induces vitellogenin synthesis and consequent oviposition. Sensitivities to juvenile hormone analogue in the stimulation of vitellogenin synthesis depended on the stage of diapause: pre-diapause period, diapause period and post-diapause period. The time lags between juvenile hormone analogue application and vitellogenin induction in the haemolymph were shorter in the pre- and post-diapause period than that in diapausing females.

Effects of B chromosomes on development in grasshopper embryos

Pre- and post-diapause embryonic development was described in Myrmeleotettix maculatus in 24 stages up to hatching. The rate of development and mitotic index of 0B, 1B and 2B karyotypes in males and females were compared in the laboratory in material from two disjunct locations. The overall influence of one B chromosome on development does not appear to be major ; however, higher numbers of Bs have a more noticeable effect. The B chromosome quite clearly slows down the early prediapause development of male embryos, and individuals with 2B or 3B chromosomes are on average retarded in the later stages of the post-diapause period prior to hatching. The presence of B chromosomes produces a variety of chromosomally mutant embryos, many of which are arrested prior to diapause and few develop to hatching. The results are discussed in relation to the maintenance of the B chromosome polymorphism in this insect.

Effects of temperature on the rates of oxygen consumption during morphogenesis and diapause in the egg stage of Letopterna dolobrata (Heteroptera, Miridae).

Oxygen consumption at 25°C was measured continously throughout the egg stage of Leptopterna dolobrata (more than 9 months).The rate of O2-uptake (μl O2/100 eggs · 1 h) is low in freshly laid eggs. Maintaining the eggs at a constant temperature of 16°C, respiration rises abruptly from the first day after oviposition and continues rising steadily for 3 days, reaching an average value of 1.4 μl. Oxygen consumption persists at or near this high level during the developmental phase of prediapause, which lasts about 15 days. After some days of oscillating high and low values, respiration decreases, and from the 24th day a low level (0.3-0.4 μl) is reached. If the eggs are incubated at 16°C continuously, this low diapause-level is maintained until the end of the experiments (42 weeks) and diapause is terminated in a few eggs only.A significant increase in the success of hatching is obtained by exposing the eggs to a sufficient period of chilling.24 groups of diapausing eggs were chilled at 5°C for certain periods (10, 18, 22, 26, 31, and 34 weeks) and afterwards transferred to 16°C and re-incubated. The changes of their O2-uptake at 25°C were traced throughout their chilling and successive re-incubating periods.Oxygen consumption is greatly accelerated during the cold treatment of the eggs. The low values of the diapause-level are raised progressively during the first 6 weeks of chilling. After this primary rapid increase, respiration remains at a level 5-times as high as the diapause values over a period up to the 25th week at 5°C. This is almost exactly the duration of mesodiapause (6 months).The rates of O2-uptake during the subsequent re-incubation at 16°C depend on the extent of chilling. The ability of diapause-breaking is correlated to the rates of O2-uptake, measured after setting of re-incubation. If respiration never decreases by the onset of re-incubation, diapause is terminated in most of the eggs, and the rates of O2-uptake increase as re-incubation goes on towards the emergence of the larvae (postdiapause period).A preliminary interpretation of the cold-stimulated O2-uptake in diapausing Leptopterna-eggs is given.