草地螟阿格姬蜂的滞育诱导和滞育茧的低温贮藏

为了阐明环境因子对草地螟阿格姬蜂Agrypon flexorium (Thunberg)滞育诱导作用, 测定了5个光周期和4个温度处理对阿格姬蜂的滞育诱导和该蜂感受光周期的敏感虫态以及不同时间段低温贮藏对滞育虫茧的影响。结果表明： 在17~23℃、 光照时间10~14 h范围内, 随着温度的降低和光照时间的缩短, 滞育率明显提高。高温能抵消短光照对滞育诱导的影响, 在26℃下, 短光照不能诱导滞育。因此, 低温和短光照是诱导草地螟阿格姬蜂滞育的主要因子。草地螟阿格姬蜂感受滞育信号的敏感虫态为卵和1龄幼虫。卵和1龄幼虫感受滞育信号以后, 需要在滞育环境中发育到老熟幼虫才能全部进入滞育。将室内诱导的滞育茧在4℃左右环境条件下冷藏80 d, 成蜂的羽化率和寄生能力与没有冷藏的非滞育茧差异不显著, 冷藏120 d, 滞育茧仍有71.7%可以正常羽化。结果说明,可在17℃,光周期8L∶16D条件下对寄生后3 d内的草地螟Loxostege sticticalis幼虫进行滞育诱导, 滞育后的虫茧最佳贮藏时间为80 d, 不宜超过120 d。本研究为室内扩繁、 防止蜂源退化、 控制寄生蜂发育时间以便适时释放提供了参考依据。     

Selection in the absence of males does not affect male-female conflict in the parasitoid wasp Leptopilina clavipes (Hymenoptera: Figitidae)

Divergent reproductive interests of males and females can lead to sexually antagonistic coevolution (SAC). In the absence of males, adaptations evolved under SAC are released from selection and expected to deteriorate. In this study, we investigated this prediction using two populations of the parasitoid wasp Leptopilina clavipes, one arrhenotokous and one thelytokous. Thelytokous females were induced to produce sons by curing them of their Wolbachia-infection. We examined whether thelytokous males were less able to inhibit female remating than arrhenotokous males and whether thelytokous females were more susceptible to male-induced longevity reduction than arrhenotokous females. The results showed that females were monandrous, regardless of whether mated with an arrhenotokous or thelytokous male. While ongoing courtship of males reduced female life span, there was no longevity cost of mating for either arrhenotokous or thelytokous females. Our results therefore do not support the idea that adaptations evolved under SAC deteriorate under prolonged female-only selection.     

The joint effect of temperature and host species induce complex genotype-by-environment interactions in the larval parasitoid of Drosophila, Leptopilina heterotoma (Hymenoptera: Figitidae)

Phenotypic plasticity and genotype-by-environment interactions are usually studied by testing environmental factors separately. However, several environmental factors may vary simultaneously across the geographic range of a species, and thus interact to drive phenotypic and genotypic evolution. Here, we address the question of the interaction between two environmental factors in the case of a koinobiont parasitoid of Drosophila , Leptopilina heterotoma (Hymenoptera: Figitidae). Using two allopatric parasitoid lines, we analysed the joint effect of developmental temperature and host species on two major fitness components (pre-imaginal survival and fecundity) of emerged parasitoids. Our results indicate that both environmental factors strongly interact to shape the parasitoid phenotype. Moreover, complex genotype-by-environment interactions appeared that can even invert the relative fitness of the two parasitoid lines.     

Cytology of Wolbachia-induced parthenogenesis in Leptopilina clavipes (Hymenoptera: Figitidae).

Parthenogenesis induced by cytoplasmatically inherited Wolbachia bacteria has been found in a number of arthropod species, mainly Hymenoptera. Previously, two different forms of diploidy restoration have been reported to underlie parthenogenesis induction in Hymenoptera by Wolbachia. Both are a form of gamete duplication, but each differs in their timing. We investigated the cytology of the early embryonic development of a Wolbachia-infected strain of the parasitoid wasp Leptopilina clavipes and compared it with that of an uninfected sexual strain. Both strains have a similar meiosis. In the infected parthenogenetic strain, diploidy is restored by anaphase restitution during the first somatic mitosis, similar to Trichogramma, but not to Muscidifurax. Our results confirm the occurrence of different cytological mechanisms of diploidy restoration associated with parthenogenesis-inducing Wolbachia in the order Hymenoptera.     

Sexual functionality of Leptopilina clavipes (Hymenoptera: Figitidae) after reversing Wolbachia-induced parthenogenesis

Females infected with parthenogenesis-inducing Wolbachia bacteria can be cured from their infection by antibiotic treatment, resulting in male production. In most cases, however, these males are either sexually not fully functional, or infected females have lost the ability to reproduce sexually. We studied the decay of sexual function in males and females of the parasitoid Leptopilina clavipes. In western Europe, infected and uninfected populations occur allopatrically, allowing for an investigation of both male and female sexual function. This was made by comparing females and males induced from different parthenogenetic populations with those from naturally occurring uninfected populations. Our results indicate that although males show a decay of sexual function, they are still able to fertilize uninfected females. Infected females, however, do not fertilize their eggs after mating with males from uninfected populations. The absence of genomic incompatibilities suggests that these effects are due to the difference in mode of reproduction.     

中红侧沟茧蜂滞育诱导和滞育茧的冷藏

中红侧沟茧蜂Microplitis mediator (Haliday)是夜蛾科害虫低龄幼虫的重要寄生蜂。田间实验表明,在冀中地区秋季田间条件下,当日平均气温为21.5℃、日平均光照时间为12 h 33 min时,少数个体进入滞育;当气温降至17.9℃以下、日光照时间缩短到11 h 45 min以下时,全部个体进入滞育。室内模拟实验结果表明,在17～26℃、光照时间10～14 h范围内,随着温度的降低和光照时间的缩短,滞育率明显提高。高温能抵消短光照对滞育诱导的影响,在26℃下,短光照不能诱导滞育。因此,低温和短光照是诱导该种天敌昆虫滞育的主要因子。中红侧沟茧蜂感受滞育信号的敏感期为低龄幼虫期,以预蛹（茧）进入滞育。低龄幼虫感受滞育信号以后,需要在滞育环境中发育到老熟幼虫才能全部进入滞育。将室内诱导的滞育茧在4℃左右环境条件下冷藏240天,成蜂的羽化率和寄生能力与没有冷藏的非滞育茧差异不显著;冷藏300天,滞育茧仍有81.4%可以正常羽化。本项研究结果为中红侧沟茧蜂的规模化、标准化生产提供了科学的依据。     

Revision of the Asian species of genus Xyalaspis Hartig, 1843 (Hymenoptera: Figitidae: Anacharitinae)

A revision of genus Xyalaspis (Hymenoptera: Anacharitinae) in Asia is given. Xyalaspis lituricis Belizin, 1965 is synonymized with Xyalaspis hyalina Belizin, 1951. Four new species are described: Xyalaspis esbelta n. sp., Xyalaspis dimorphica n. sp., Xyalaspis orientalis n. sp., and Xyalaspis siamensis n. sp. Diagnostic characters are illustrated and data about biology, distribution and morphological variability of the studied species are discussed. A key to the Asian species of this genus is included.     

Taxonomy and phylogeny of Leptopilina species (Hymenoptera: Cynipoidea: Figitidae) attacking frugivorous drosophilid flies in Japan,with description of three new species

Despite the intensive use of the Leptopilina genus and its drosophilid hosts as model systems in the study of host–parasitoid interactions, the diversity and distribution of the species occurring in the Asian region remain elusive. Here we report the phylogeny of Japanese Leptopilina species attacking frugivorous drosophilid flies, based on COI, ITS1 and ITS2 sequences. Consistent with molecular data, hybridization experiments and morphological examination, five species were recorded in Japan: Leptopilina heterotoma, L. victoriae and three new species, two occurring in the Ryukyu archipelago, L. ryukyuensis and L. pacifica, and another species, L. japonica, distributed in Honshu and Hokkaido. Leptopilina japonica is further divided into two subspecies, L. j. japonica occurring in Japan, and L. j. formosana occurring in Taiwan. According to these results, we discuss the evolution, speciation and colonization history of Japanese Leptopilina species.     

Adaptive self- and conspecific superparasitism in the solitary parasitoid Leptopilina heterotoma (Hymenoptera: Eucoilidae)

One of the foraging decisions facing parasitoids is whetherto accept (superparasitize) or reject hosts that have alreadybeen parasitized. An important distinction is whether the hosthas been parasitized by the female parasitoid herself or bya conspecific. In solitary parasitoids, the pay-off from anegg laid in the latter host type (conspecific superparasitism)is the probability that the second egg wins the competitionfor the host and results in an offspring. The pay-off from anegg laid in the former type (self-superparasitism) increaseswith an increasing probability that another female will superparasitizethe host in the near future. When this probability equals one,self-superparasitism and conspecific superparasitism have thesame payoff. However, conspecific superparasitism will generallyhave a higher pay-off than self-superparasitism. It will thereforebe beneficial for a female parasitoid to be able to distinguishbetween a host she parasitized and one parasitized by a conspecific.The degree of benefit depends on the probability of conspecificsuperparasitism in the near future. Using an optimal diet model,I show that when a parasitoid encounters a patch containinga mixture of unparasitized and already-parasitized hosts, afemale that can distinguish between the two types of parasitizedhosts gains more offspring than a female without this ability.However, when parasitoids search a patch together with conspecifics,it is adaptive to self-superparasitize, and the pay-off fromthis ability may be negligible. It is therefore predicted thatwhen a female parasitoid searches a partially depleted patchalone, it will reject the hosts parasitized by itself more frequentlythan hosts parasitized by conspecifics. In contrast, femaleparasitoids searching together are predicted to accept hoststhat they parasitized themselves much more often. The resultsshow that the solitary parasitoid Leptopilina heterotoma (Hymenoptera:Eucoilidae) is able to distinguish between hosts that it parasitizedand hosts parasitized by conspecifics. The predictions of themodel are met in a second experiment that shows that L. heterotomaself-superparasitizes when the probability of conspecific superparasitismis high.     

Diapause termination in two species of tropical butterfly, Euploea core (Cramer) and Euploea sylvester (Fabricius) (Lepidoptera: Nymphalidae)

Abstract This study examined the factors used as cues for diapause termination by two Euploea species. Euploea core and E. sylvester were collected from two overwintering sites at Chillagoe, Queensland. Under tropical wet-season conditions, more butterflies terminated diapause (approximately 60%) than those kept under dry-season conditions (approximately 40%). However, 100% diapause termination occurred only when butterflies were kept under wet-season conditions and were fed with honey. For reproductive success, Euploea species need to terminate diapause rapidly to synchronise oviposition with fresh, rapid growth of their larval host plants, which often occurs after rain. The presence of rainfall, increased temperature and long days alone is not a fail-safe set of cues for this event. Our results suggest that food (as nectar), in conjunction with these combined environmental factors, provide Euploea species with a reliable signal that larval host resources are available for oviposition.     

白蛾周氏啮小蜂滞育诱导及滞育后发育

本研究针对人工繁育白蛾周氏啮小蜂Chouioia cunea Yang过程中出现的小蜂滞育现象, 对其滞育诱导的光周期反应及敏感光照虫态进行了调查。结果表明: 沈阳地区的白蛾周氏啮小蜂属长日照型昆虫, 以老熟幼虫进入滞育状态, 但在不同的温度条件下诱导滞育的临界光周期不同, 在18℃时诱导滞育的临界光周期处于13L∶11D和14L∶10D之间; 在21℃和24℃时诱导滞育的临界光周期变短, 处于12L∶12D和13L∶11D之间。白蛾周氏啮小蜂滞育诱导的敏感光照虫态为幼虫期, 且以幼虫的后期最为敏感, 但整个幼虫期接受短光照对滞育的形成更为有利。通过观察白蛾周氏啮小蜂滞育后在18℃, 21℃, 24℃和30℃的恒温条件下的发育历期, 由最小二乘法计算出白蛾周氏啮小蜂老熟幼虫滞育后发育起点温度和有效积温分别为14.60±0.31℃和209.38±8.72日·度。这些结果可为进一步研究白蛾周氏啮小蜂的种蜂长期保存技术和指导商品蜂生产, 正确把握放蜂时机提供理论依据。     

The genetic basis of male fertility in relation to haplodiploid reproduction in Leptopilina clavipes (Hymenoptera: Figitidae)

Traits under relaxed selection are expected to become reduced or disappear completely, a process called vestigialization. In parthenogenetic populations, traits historically involved in sexual reproduction are no longer under selection and potentially subject to such reduction. In Leptopilina clavipes, thelytokous (parthenogenetic) populations are infected by Wolbachia bacteria. Arrhenotokous populations do not harbor Wolbachia. When antibiotics are applied to infected females, they are cured from their infection and males arise. Such males are capable of producing offspring with uninfected females, but with lower fertilization success than sexual males. This can be attributed to the lack of selection on male fertility in thelytokous lines. In this study we used this variation in L. clavipes male fertility to determine the genetic basis of this trait. Males from cured thelytokous populations were crossed to females from uninfected populations. Using AFLP markers, a genetic linkage map was generated, consisting of five linkage groups and spanning a total distance of 219.9 cM. A single QTL of large effect (explaining 46.5% of the phenotypic variance) was identified for male fertility, which we call male fertility factor (mff). We discuss possible mechanisms underlying the effect of mff, as well as mechanisms involved in vestigialization of traits involved in sexual reproduction.     

Response of two parasitoid species (Hymenoptera: Braconidae,Figitidae) to tephritid host and host food substrate cues

The Neotropical‐native figitid Aganaspis pelleranoi (Brèthes) and the Asian braconid Diachasmimorpha longicaudata (Ashmead) are two parasitoids of Tephritidae fruit flies with long and recent, respectively, evolutionary histories in the Neotropics. Both species experienced a recent range of overlap. In Argentina, A. pelleranoi is a potential species in biological control programs against the pestiferous tephritid species, Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann), whereas D. longicaudata is already used in open‐field releases against Medfly in central‐western Argentina. To characterize the host‐foraging strategies of A. pelleranoi and D. longicaudata, olfactometer experiments were conducted comparing responses to C. capitata and A. fraterculus larvae, in two kinds of food substrate: fruit and artificial larval medium. To control the possible influence of host larvae used for parasitoid rearing on olfactory response, two strains of both parasitoid species, reared on both tephrtid species, were studied. Volatiles directly emanating either from A. fraterculus or C. capitata larvae may be detected by both A. pelleranoi and D. longicaudata, although chemical stimuli originating from the combination of host larvae and the habitat of the host were preferred. However, olfactory cues associated with host larvae probably play a relevant role in host searching behaviour of A. pelleranoi, whereas for D. longicaudata, the host‐habitat olfactory stimuli would be highly essential in short‐range host location. The strain of the parasitoids did not affect host search ability on the two tephritid species evaluated. These evidences are relevant for mass production of both parasitoids and their impact following open‐field augmentative releases.     

Diapause and seasonal life cycle strategy in the house spider, Achaearanea tepidariorum (Araneae, Theridiidae)

Abstract In order to elucidate the mechanism regulating its seasonal life cycle, the photoperiodic response of Achaearanea tepidariorum has been analysed. Nymphal development was faster in long-day and slower in short-day photoperiods. The combined action of low temperature, poor food supply and short daylength induced diapause at an earlier developmental stage than short days alone. Thus, photoperiod is a primary factor inducing nymphal diapause, but the diapausing instar is influenced by both temperature and food supply. Hibernating nymphs became unresponsive to photoperiod in late December. After hibernation, however, sensitivity was restored and the nymphs remained sensitive to photoperiod throughout their life. This spider could also enter an imaginal or reproductive diapause. Photoperiod was again a primary inducing factor and temperature modified the photoperiodic response to some extent. The induction of the reproductive diapause was almost temperature-compensated whereas development was not. So the involvement of a photoperiodic counter system was suggested. Irrespective of whether the nymph had experienced diapause or not, the imaginal diapause was induced in response to a short-day photoperiod after adult moult. Based on these observations, the seasonal life cycle and the adaptive significance of nymphal and imaginal diapause are discussed.     

New distributional and host records for the parasitoid Gronotoma adachiae (Hymenoptera: Figitidae: Eucoilinae) in Asia

The parasitoid Gronotoma adachiae is reported from Vietnam for the first time. The vegetable leaf miner Liriomyza sativae (Diptera: Agromyzidae) is a new host record. The G. adachiae specimens collected in Yunnan Province are the second record of this parasitoid from China.     

Overwintering strategies and cold hardiness of two aphid parasitoid species (Hymenoptera: Braconidae: Aphidiinae)

The role of winter diapause in two aphid parasitoid species, Aphidius ervi Haliday and Aphidius rhopalosiphi DeStefani-Peres (Hymenoptera: Braconidae: Aphidiinae), in host synchronization and the induction of cold hardiness was investigated. Parasitoids were reared during three successive generations on Sitobion avenae Fabricius, at 15 degrees C under a photoperiod of 9 h light 15 h dark. Although these conditions are known to be strongly diapause inducing, neither parasitoids showed an incidence of diapause above 65% over the three generations; the rest of the population underwent quiescence. In both parasitoid species, diapausing mummies exhibited greater cold hardiness than non-diapausing mummies, resulting in significantly lower supercooling points (SCP) and in a higher survival rate during long-term exposures at 0 and -10 degrees C. The induction of increased cold hardiness in parasitoids was thus associated with the diapause state. SCPs of third instar larvae of S. avenae were similar to those of non-diapausing mummies of both parasitoid species, but significantly higher than those of diapausing mummies. The effect of winter climate on the stability of the host-parasitoid interaction is discussed.     

Egg-laying experience and acceptance of parasitized hosts by the parasitoid,Leptopilina heterotoma (Hymenoptera: Eucoilidae)

The influence of egg-laying experience on the response of females of the eucoilid parasitoid,Leptopilina heterotoma, to parasitized and unparasitizedDrosophila melanogaster host larvae was examined under more controlled conditions than those used in past studies. In laboratory assays, we precisely manipulated both the number of eggs laid by females and the kind of larvae (parasitized versus unparasitized) in which the eggs were laid. We found that the tendency to avoid laying eggs in parasitized hosts depended markedly on whether or not eggs had been laid previously, but depended little on whether those eggs had been laid in parasitized or unparasitized hosts. The observed effect of general egg-laying experience on avoidance of parasitized hosts may reflect responses to either changes in the wasp's internal state (perhaps, changes in egg load) or changes in the wasp's neural representation of the external environment (such as those presumed to occur during learning). In light of these results, we offer a tentative reinterpretation of several earlier studies.     

Diapause induction in the oblique-banded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae): Role of photoperiod and temperature

Induction of diapause in the larval stage of the oblique-banded leafroller, Choristoneura rosaceana (Harris), was found to be dependent on both photoperiod and temperature. At constant temperatures of 24, 20 and 16°C, short photoperiods induced diapause. The critical photoperiod was between 14–15 h of light per day at 20 and 16°C. At 14 h light: 10 h dark, all larvae expressed diapause. Temperature had a modifying effect, and slightly shifted the larval response to diapause-inducing photoperiods. High constant temperatures of 28°C and above induced diapause in some individuals (< 20%), while fluctuating temperatures of 32 and 16°C in a 12-h cycle resulted in 67% diapause induction, suggesting that diapause could also be induced by fluctuating temperatures, particularly if the higher temperature exceeds 25°C.The first- and the second-instar larvae were the only two stages sensitive to diapause induction. Exposure of adult, egg and third, fourth, and fifth-larval instars to diapause-inducing conditions did not produce diapause. Although diapause was induced in the first or the second instars, it was always expressed in the third or fourth instar.