Interspecific parasite exchange in a mixed colony of birds

Studies of avian host-parasite interactions rarely include consequences of relationships among hosts for either the host or parasite species. In this study, we examine the ectoparasitic burden of adult and nestling European bee-eaters (Merops apiaster) and rock sparrows (Petronia petronia) in a mixed colony. We found that (1) each bird species had its own species of lice; (2) hematophagous mites parasitized both adults and nestlings of both bird species; (3) Carnus hemapterus, a common parasite of nestling bee-eaters, also infested rock sparrow nestlings, a species not previously described as a host for this dipteran; and (4) whereas C. hemapterus did not show high host specificity within the colony, the emergence of adult flies was synchronized with the start of hatching in bee-eater nests. We suggest that coexistence of these 2 bird species results in parasite exchange, bee-eaters obtaining mites from sparrows and sparrows becoming infested by C. hemapterus. Differences in the detrimental effects of parasite transfer for each host species may result in a process of apparent competition mediated by shared parasites. Interspecific parasite exchange is an important aspect of host-parasite relationships in mixed colonies, which requires further attention.     

Intra‐specific variability in life‐cycle synchronization of an ectoparasitic fly to its avian host

The role of environmental and host‐associated factors in synchronization of host–parasite life‐cycles is an important question of evolutionary ecology. Yet, only handsome of studies examined this question at the intraspecific level. Here we explore how host‐associated traits, such as breeding phenology and host breeding habitat, can influence parasite phenology and co‐occurrence at different spatial scales. We studied the system comprised of a generalist ectoparasitic fly Carnus hemapterus and one of its avian hosts, the European roller Coracias garrulus. Inter‐annual variation in phenology was larger for parasites than hosts. Host predictability in terms of occurrence and phenological regularity was moderate, suggesting that this resource can be difficult to be tracked by the parasite. A large proportion of flies consistently emerged before the appearance of suitable host resources at both the nest and population level. Consequently, we revealed low and highly variable inter‐annual host–parasite synchronization rates. Nevertheless, we found that parasites from nests of early and progressively earlier breeding European rollers were more synchronized with their hosts than parasites from nests of late and progressively later breeding hosts, respectively. Temporal trends in host suitability and parasite emergence at the population scale suggest that other mechanisms, such as dispersal or exploitation of other host species, ensure parasites access to resources and counteract asynchrony with the host at the nest scale.     

Nest excavation does not reduce harmful effects of ectoparasitism: an experiment with a woodpecker, the northern flicker Colaptes auratus

It has been hypothesized that it is adaptive for birds to build new nests annually in order to avoid the accumulation of ectoparasites. Previous studies on costs of ectoparasitism have focused on cavity nesters in nestboxes while largely ignoring reproductive consequences in natural tree cavity nests, the context where nest selection strategies presumably evolved. To see whether ectoparasitism could be a driving selective force in the evolution of nest excavation in a woodpecker, I experimentally fumigated a subset of freshly excavated cavities and a subset of reused cavities of the northern flicker Colaptes auratus and compared reproductive performance with a set of control nests. The main ectoparasite of nestlings, a blood-sucking fly Carnus hemapterus , may have appeared one or two days earlier in reused nests but there was no difference between fresh and reused nests in intensities of flies one week post-hatching. Prevalence of parasitism reached 100% in both reused and freshly-excavated control nests in the second week. Nestlings from control nests had lower body mass residuals than those from fumigated nests after 15 d and fledged at a lower weight, suggesting that ectoparasitism by C. hemapterus was costly. However, fresh nest construction was no benefit, likely because the high dispersal ability of the ectoparasite meant all nests were colonized rapidly. Parents did not adjust provisioning effort according to parasitism as delivery rates did not differ between control and fumigated nests but delivery rates increased with brood size.     

Mixed life-history strategies in a local population of the ectoparasitic fly Carnus hemapterus

A major issue for the proper understanding of the evolution of life-cycle histories is the regulation of voltinism and its variation. Diapause characteristics are known to regulate voltinism, but the underlying mechanisms are poorly understood. This paper studies diapause duration and voltinism variation in a haematophagous diptera parasitizing 2 sympatric hosts with very different breeding phenologies. We hypothesize that bivoltinism will be more frequent in carnid flies parasitizing an early breeding, multi-brooded species than in flies parasitizing a late breeder, single-brooded species. We obtained evidence of the co-occurrence of uni- and bivoltinism in both clutches of the multi-brooded Spotless starling (Sturnus unicolor) as well as in clutches of the single-brooded European roller (Coracias garrulus). Unexpectedly, the proportion of bivoltine flies was similar in both host species. A remarkable degree of host-parasite synchronization at the population level was found for bivoltine flies. Our findings reveal the facultative nature of diapause in Carnus. We discuss the influence of abiotic conditions and host availability on polymorphism in life-history cycles and the consequences both for the parasite and the host.     

Are parasite intensity and related costs of the milichiid fly Carnus hemapterus related to host sociality?

Ectoparasites have often been shown to have detrimental effects on their host. Not much is known, however, about determinants of infestation, e.g. the question of which factors affect distribution and occurrence of parasites on different host species (degree of host specificity) and their infestation rates. In this study we examine possible effects of host determinants on parasite intensity of Carnus hemapterus (Carnidae), an ectoparasitic fly on nestling birds, in the European bee-eater (Merops apiaster), which is a common host of C. hemapterus. Our results show that European bee-eaters seem to be one of the most heavily infested host species of C. hemapterus. We found that brood size, nestling age, and colony size are the most important determinants of infestation by C. hemapterus. This parasite seems to prefer medium-sized bee-eater chicks and to select them according to their condition. Our results further suggest a negative effect of C. hemapterus on chick development.     

Diapause development in early and late emerging phenotypes of Delia floralis

The turnip fly, Delia floralis Fall6n （Diptera： Anthomyiidae） is an important insect pest of brassica vegetable crops in the holarctic region. Different populations have strongly varying temperature requirements for fly emergence, a challenge for accurate prediction of activity. This study focused on diapause development in one early and one late emerging phenotype. The physiological state after various treatments was deduced from emergence data. Our results showed a slow diapause progression at chilling conditions for both populations and diapause ended about 7 months after pupae were formed for the early population. For the late population held at 4℃ diapause did not end, no matter how long the duration of chilling. These pupae required a period with elevated temperatures above 6~C to continue development. At constant non-chilling conditions （18℃） from the time pupae were formed both populations completed diapause most rapidly. These results indicate that chilling delayed, rather than accelerated development and was not a prerequisite for diapause development. For post-diapause, results indicated a linear relationship between rate of development and temperature within the range of 6-18℃and a theoretical base temperature for development of about 2℃ for both populations. In conclusion, D. floralis pupae are in diapause throughout a long winter period, and delayed emergence of the late population appears to be caused by prolonged diapause regulated by a developmental temperature threshold. The study has added information on the biology of turnip fly populations, a prerequisite for improved pest control.     

Influence of a bimodal emergence strategy of a Dipteran host on life-history traits of its main parasitoids

Abstract. 1. Among a great diversity of other strategies, insects have evolved polymodal emergence patterns that can increase survival in the face of annual variations in environmental conditions. Delia radicum L. (Diptera: Anthomyiidae) is a polyvoltine pest that attacks several cultivated cruciferous species. At the time of emergence, most populations show a polymodal emergence of type A (i.e. all individuals that enter diapause in the same year terminate diapause the following growing season, and exhibit a bimodal emergence curve). This results in the occurrence of two sympatric phenotypes, early and late, which differ by the timing of adult emergence in both diapausing and non‐diapausing generations. 2. In Brittany, D. radicum pupae can be heavily parasitised by three parasitoids, Aleochara bilineata Gyll. (Coleoptera: Staphylinidae), Aleochara bipustulata L., and Trybliographa rapae (Hymenoptera: Eucoilidae). As in all parasitoids species, the successful development of both Aleochara species and T. rapae larvae depends mainly on the amount and quality of the food provided by the host. 3. The relationship between early and late host phenotype and (i) the parasitism efficiency, (ii) emergence patterns, and (iii) host selection behaviour were investigated for the three parasitoid species. 4. Depending on parasitoid species and their different parasitism and development mode, the results reveal that host phenotype can influence (i) survival and development time in T. rapae, and (ii) survival in Aleochara species. Aleochara larvae did not appear to discriminate between early and late host pupae on the basis of phenotype, but rather selected them according to their developmental stage. Furthermore, it was discovered that the same phenological strategy occurred in T. rapae and in D. radicum. However, for D. radicum the results indicate that such a strategy has a cost as the longer development time of late host pupae results in a longer period of time favourable for parasitism.     

Physiological and biological patterns of a highland and a coastal population of the European cherry fruit fly during diapause

Adult emergence of univoltine temperate insect species and its synchronization with specific host phenological stages is mainly regulated by obligatory pupal diapause. Although a few studies have investigated the factors affecting diapause intensity, little attention has been paid to the physiological alterations and metabolic regulation that take place during diapause. Here, we describe differences in diapause between a highland and a coastal Greek population of the European cherry fruit fly Rhagoletis cerasi, a major pest of sweet and sour cherries in many European countries. Pupae of both populations were exposed to the environmental conditions prevailing in the two areas and diapause termination was observed under laboratory conditions. The regulation of energetic metabolites during the long pupae stage was examined under both field and laboratory conditions. Differences in diapause intensity revealed that the two populations have adapted to the local geographical and climatic conditions and have different requirements for low temperatures to terminate diapause. The coastal population undergoes a shorter diapause and adults emerge more rapidly, especially in the highland area. The highland population failed to terminate diapause (<40% adult emergence) in the coastal area. Both populations draw on their major energetic reserves (lipids and protein) similarly during diapause. Nevertheless, regulation of carbohydrate and glycogen reserves seems to vary between the populations: major peaks of these stored nutrients occur on different dates in the two populations, suggesting a differential regulation. Differences in diapause intensity imply a genetic differentiation between the two populations. The importance of our findings in understanding the physiological patterns during obligatory diapause of a univoltine insect species, as well as the practical implications for the development of specific phenological models for the European cherry fruit fly are discussed.     

Diapause termination of Rhagoletis cerasi pupae is regulated by local adaptation and phenotypic plasticity: escape in time through bet‐hedging strategies

Persistence and thriving of univoltine, herbivore insect species of the temperate zone rely on obligate diapause response that ensures winter survival and synchronization with host phenology. We used a stenophagous fruit fly (Rhagoletis cerasi) with obligate pupae diapause to determine genetic and environmental effects on diapause intensity of geographically isolated populations with habitat heterogeneity. Pupae from two Greek and one German populations with various gene flow rates were exposed at five constant chilling temperatures (0–12 °C) for different durations and then incubated at a high temperature until all adults have emerged. Pupae diapause intensity differs among Greek and German populations, suggesting an adaptive response to habitat heterogeneity (mostly differences in phenology patterns of local host cultivars). Moderately warm winter temperatures, such as 8 °C, promote diapause termination in all three populations. Insufficient chilling (short duration or warmer temperatures) regulates the expression of prolonged dormancy. Interestingly, extended chilling (longer than required for terminating diapause) ‘return’ pupae to another (facultative) cycle of dormancy enabling adults to emerge during the next appropriate ‘window of time’; a strategy first time reported for univoltine insects. Consequently, diapause duration of R. cerasi is determined both by i) the adaptive response to local climatic conditions (annual dormancy) and ii) the plastic responses to interannual climatic variability resulting in two types of long life cycles within populations, prolonged and facultative dormancy as response to insufficient chilling and extended exposure to chilling, respectively. Long life cycles are expressed as a part of dormancy bet‐hedging strategies of R. cerasi populations.     

高温条件下棉铃虫化蛹率、夏滞育率和蛹重的变化

在预蛹期,高温处理能诱导棉铃虫蛹进入夏滞育。本实验着重就33～39℃的变温下滞育蛹和未滞育蛹的失重动态进行了对比研究,同时以常温（27℃）下蛹作为参照。研究发现： 在33～39℃的变温条件下,棉铃虫化蛹率显著低于其在常温下的化蛹率,且所化蛹中有63.2%的雄性和10.9%的雌性进入高温夏滞育,其中高温滞育蛹和未滞育蛹分别都轻于正常发育蛹。化蛹后第2日至第5日期间,高温滞育蛹失重量显著低于高温未滞育蛹和正常发育蛹的失重量,分别为3.62、13.30和5.49 mg;蛹期总失重量结果与化蛹后第2～5日间蛹失重量趋势一致,高温滞育蛹、未滞育蛹和正常发育蛹失重量分别为15.60、49.35和26.30 mg。蛹失重动态研究发现高温滞育蛹在夏滞育期间其失重曲线平缓,显著低于高温未滞育蛹和正常发育蛹;高温滞育蛹滞育解除后,其失重曲线与正常发育蛹的失重趋势基本一致。结果表明,棉铃虫夏滞育蛹能通过维持低的代谢水平来度过不利环境,具有一定的生态适应意义。     

Optimal Low Temperature and Chilling Period for Both Summer and Winter Diapause Development in Pieris melete: Based on a Similar Mechanism

The cabbage butterfly, Pieris melete hibernates and aestivates as a diapausing pupa. We present evidence that the optimum of low temperature and optimal chilling periods for both summer and winter diapause development are based on a similar mechanism. Summer or winter diapausing pupae were exposed to different low temperatures of 1, 5, 10 or 15°C for different chilling periods (ranging from 30 to 120 d) or chilling treatments started at different stages of diapause, and were then transferred to 20°C, LD12.5∶11.5 to terminate diapause. Chilling temperature and duration had a significant effect on the development of aestivating and hibernating pupae. The durations of diapause for both aestivating and hibernating pupae were significantly shorter when they were exposed to low temperatures of 1, 5 or 10°C for 50 or 60 days, suggesting that the optimum chilling temperatures for diapause development were between 1 and 10°C and the required optimal chilling period was about 50–60 days. Eighty days of chilling was efficient for the completion of both summer and winter diapause. When chilling periods were ≥90 days, the durations of summer and winter diapause were significantly lengthened; however, the adult emergence was more synchronous. The adaptive significance of a similar mechanism on summer and winter diapause development is discussed.     

松毛虫赤眼蜂滞育诱导及解除条件研究

【目的】以柞蚕Antheraea pernyi卵为繁殖寄主,对松毛虫赤眼蜂Trichogramma dendrolim滞育诱导及解除条件进行研究,以解决赤眼蜂工厂化生产和大面积应用中面临的的中、长期储存问题。【方法】通过观测不同发育阶段(寄生柞蚕卵在26℃培养40、96和144 h)、滞育诱导温度(10、13和16℃)和诱导时间对松毛虫赤眼蜂滞育的影响,确定松毛虫赤眼蜂滞育诱导条件;通过观测滞育诱导温度和滞育后的贮藏温度对滞育解除的影响,确定松毛虫赤眼蜂滞育解除条件。【结果】在松毛虫赤眼蜂的不同发育阶段对其进行持续的低温刺激均能使其导入滞育,但以小幼阶段(26℃培养40 h)开始效果最佳,寄生卵在26℃培养40 h后,转入10℃和13℃下连续诱导31 d,滞育率可达100%和99.12%。滞育诱导温度和滞育后的贮藏温度对松毛虫赤眼蜂解除滞育所需时间和解除滞育后的羽化出蜂率有较大影响,10℃诱导滞育后置于1℃冷藏的赤眼蜂解除滞育所需时间最短,解除滞育后的羽化出蜂率和单卵出蜂数更高,更耐储存。此条件下冷藏约30 d开始打破滞育,在正常发育下温度下羽化出蜂,60 d羽化出蜂率达到95.24%,冷藏4个月后羽化出蜂率仍在60%以上,单卵出蜂数高于50头。【结论】松毛虫赤眼蜂最佳滞育诱导条件为26℃培养40 h后,转入10℃连续低温诱导31 d;最佳滞育解除条件为1℃低温储存,但储存期不能超过4个月。     

The effect of parasite density on host colonisation success by a mobile avian ectoparasite

1. Full understanding of the dynamics of host–parasite interactions requires elucidation of the principles governing host colonisation. With respect to mobile parasites, little is known about their dispersal behaviour and the factors affecting host colonisation success. 2. Here, the effect of parasite density manipulations on the colonisation success of the carnid fly Carnus hemapterus, an avian ectoparasite, was experimentally explored. 3. Most host nests were colonised within the same breeding season, but the abundance of flies colonising the nests varied broadly both within and between years. 4. Experimental increase in the density of carnid flies in the vicinity of host nests did not result in higher parasite abundance in these nests. Host colonisation success in terms of parasite abundance was not related to indices of parasite density around host nests. 5. Parasite abundance in colonised host nests was positively related to host density and brood mass and negatively related to date. Host nests in trees held fewer carnid flies than those on cliffs and farmhouses. 6. The dispersal ability of C. hemapterus is apt for rapid colonisation of new host nests, but it is unable to explain the broad heterogeneity in parasite abundance between host nests.     

Obligate annual and successive facultative diapause establish a bet‐hedging strategy of Rhagoletis cerasi (Diptera: Tephritidae) in seasonally unpredictable environments

To cope with temporal and spatial heterogeneity of habitats, herbivorous insects in the temperate zone usually enter diapause that facilitates synchronization of their life cycle with specific stages of host plants, such as fruit ripening. In the present study, we address those factors regulating dormancy responses as part of a ‘longer strategy’ to persist and thrive in temperate environments, focusing on Rhagoletis cerasi, a univoltine, oligophagous species, which overwinters as pupae and emerges when host fruits are available for oviposition at local scale. To ensure population survival and reproduction at habitats with ecological heterogeneity, R. cerasi has evolved a sophisticated diapause strategy based on a combination of local adaptation and diversified bet‐hedging strategies. Diapause duration is determined both by (i) the adaptive response to local host fruit phenology patterns (annual diapause) and (ii) the plastic responses to unpredictable inter‐annual (temporal) climatic variability that drives a proportion of the populations to extend dormancy by entering a second, successive, facultative cycle of prolonged diapause as part of a bet‐hedging strategy. Besides the dormant periods, post‐diapause development (which varies among populations) exerts ‘fine tune’ adjustments that assure synchronization and may correct possible errors. Adults emerging from pupae with prolonged diapause are larger in body size compared with counterparts emerging during the first year of diapause. However, female fecundity rates are reduced, followed by an extended post‐oviposition period, whereas adult longevity remains unaffected. Overall, it appears that R. cerasi populations are adapted to ecological conditions of local habitats and respond plastically to unpredictable environmental (climatic) conditions.     

Timing of diapause termination in relation to variation in winter climate

In temperate insects, winters are typically endured by entering diapause, which comprises a deep resting stage. Correct timing of diapause termination is vital for synchronization of emergence with conspecifics and for mobilizing resources when conditions for growth and reproduction become favourable. Although critical to survival, the intrinsic and extrinsic drivers of diapause termination timing are poorly understood. In the present study, we investigate diapause development under a range of durations (10–24 weeks) spent at different temperatures (?2 to 10 °C) in the pupal diapausing butterfly Pieris napi Linnaeus (Lepidoptera:Pieridae). We determine: (i) the maximum cold temperature for diapause development; (ii) if pupae in diapause count cold days or cold sums; and (iii) whether diapause termination is distinct or gradual. The results indicate large and idiosyncratic effects of high and low nonlethal temperatures on diapause development in P. napi. Although all temperatures tested lead to diapause termination, a thermal optimum between 2 and 4 °C is observed. Lower temperatures lead to decreased eclosion propensity, whereas higher temperatures slow down development and increase emergence desynchronization. These data suggest that, rather than a simple cold‐summing process with a distinct diapause termination point, there are trade‐offs between time and temperature at the low and high end of the thermal range, resulting in a nonlinear thermal landscape showing a ridge of increasing eclosion propensity at moderate temperatures. The present study suggests that the effects of temperature on diapause development should be included in projections on post‐winter phenology models of insects, including pest species.     

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.     

Parasitism and oviposition of Melittobia acasta on Bombus terrestris: Impact of larval overwintering and host status on pupation and adult emergence

Melittobia acasta (Walker) are microhymenopteran ectoparasitoids of the pupae and prepupae of the commercially‐used pollinator bumblebee species Bombus terrestris L. The female parasitoids puncture the host cuticle with their sting and feed oozing hemolymph. This study shows that M. acasta parasitize 100% pupae and 84% prepupae of B. terrestris but are ineffective on the larvae of the bees. The female parasitoids lay a significantly higher number of eggs on pupae (67.7 ± 16.2 female^?1) compared to prepupae (20.5 ± 14.5 female^?1). The parasitoids differ in their choice for oviposition sites and fecundity on different locations of B. terrestris pupae, and they show most preference for oviposition (32%) as well as fecundity (34.9 ± 15.1 female^?1) on the petiole of the host. Larvae of the parasitoids overwinter at low temperatures but larval overwintering duration and post‐diapause rearing on original or new hosts do not affect their pupation and adult emergence. Larvae have a higher percentage of pupation (88.0–94.4%) and adult emergence (84.4–92.9%) both on the original and the new host, thus indicate that the parasitoids are highly capable of reproduction in B. terrestris colonies.     

Life history traits of Pseudasphondylia rokuharensis (Diptera: Cecidomyiidae) affecting emergence of adults and synchronization with host plant phenology

To identify adaptive strategies of gall-inducing cecidomyiids, we studied the life history traits of Pseudasphondylia rokuharensis (Diptera: Cecidomyiidae), a univoltine species inducing fruit galls on a deciduous shrub, Viburnum dilatatum. Although univoltine gall midges that are associated with trees or shrubs are usually difficult to rear from immature stages under artificial conditions, we successfully reared P. rokuharensis from first instar to adult. Mature larvae entered diapause in autumn, and the diapause terminated after low temperature treatment (4 mo of incubation at 5 degrees C). The adults emerged within a shorter period of time than those without low temperature treatment. Thus, the diapause provides better synchronization of adult emergence in the spring. Because adults live for only a few days, this synchronization improves the chances of adults finding a mate. This is the first report on the mechanism of larval diapause termination for univoltine and tree- or shrub-associated gall midges. The numbers of days needed for adults to emerge under laboratory conditions after low temperature incubation were significantly different between two different localities. This result might suggest the possible existence of ecoclines in their life history parameters.     

温度和光周期对管侧沟茧蜂滞育诱导及滞育茧的低温冷藏

【目的】为明确诱导管侧沟茧蜂Microplitis tuberculifer 滞育的主要因子,在田间和室内研究了不同温度和光周期下管侧沟茧蜂的滞育率和滞育茧的最佳冷藏温度。【方法】田间实验分别从8月31日到9月25日每隔5 d在室外罩笼内释放管侧沟茧蜂寄生的粘虫幼虫,待寄生蜂结茧后统计子代蜂的滞育率。室内实验共设5个不同温度（16℃, 18℃, 20℃, 22℃和24℃）和7个不同光周期（6L:18D, 8L:16D, 10L:14D, 12L:12D, 14L:10D, 16L:8D和18L:6D）,分别统计寄生蜂在各个处理条件下的滞育率。【结果】在河北中部地区秋季自然条件下,8月底当日平均气温为24.4℃,日平均光照时间为12 h 51 min 时,少数蛹（5.08%）开始进入滞育;9月25日,当日平均气温为17.2℃,日平均光照时间为11 h 36 min以下时,几乎所有蛹个体进入滞育,滞育率达到99.70%。在室内人工控制条件下,当温度为22℃以上,无论光周期如何变化,管侧沟茧蜂不能进入滞育,所结茧全部为非滞育茧。温度为22℃以下存在光周期反应,在温度16℃, 18℃和20℃,光周期10L:14D时形成滞育茧数量最多,滞育率分别为100%, 89.75% 和 29.58%。可见温度和光周期二者共同影响管侧沟茧蜂的滞育。滞育茧在0℃左右条件下冷藏 240 d 和5℃左右环境条件下冷藏180 d, 成虫的羽化率和寄生能力与发育茧差异不显著(P>0.05);0℃条件下冷藏300 d,滞育茧仍有79%可以正常羽化。【结论】该寄生蜂在秋季进入滞育主要是低温条件和短光照反应相互作用的结果,滞育茧在0℃和5℃温度下至少可以保存240 d。这些结果对管侧沟茧蜂的大规模繁殖和滞育茧的保存具有重要参考价值。     

Cold-hardiness: a component of the diapause syndrome in pupae of the flesh flies, Sarcophaga crassipalpis and S. bullata

ABSTRACT. Diapausing pupae of Sarcophaga crassipalpis Macquart and S. bullata Parker reared at 20 or 25C readily survive exposure to - 10C for at least 25 days. In contrast, non-diapausing pupae produced by a variety of means are consistently intolerant of the low temperature. Non-diapausing pupae are not immediately killed by exposure to -10C: pupae exposed to the low temperature for up to 3 days proceed with pharate adult development but ultimately die before adult eclosion. Unlike many temperate zone insects, diapausing flesh fly pupae do not require a period of chilling for induction of cold-hardiness, and the attribute of cold-hardiness cannot be separated from other features of the diapause syndrome. Some cold-hardiness is already acquired during the third larval instar: diapause-destined larvae exposed to -10C are more successful in pupariating than non-diapause-destined larvae of the same age.