Notes on the biology and ecology of the parasitoids of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lep., Sesiidae) in Bulgaria. I. Apanteles evonymellae (Bouché, 1834) (Hym., Braconidae)

Aspects of the biology and ecology of Apanteles evonymellae (Bouché), a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.), were studied during the period 1987–96. One-year-old poplar ( Populus spp.) shoots infested with P. tabaniformis larvae were collected during the winter months at 11 localities in Bulgaria and examined in the field and laboratory. Apanteles evonymellae was recorded in all areas studied in Bulgaria. The mortality of P. tabaniformis caused by this parasitoid in various regions of Bulgaria varied from 2.4 to 35.4%; the average for the country was 17.3%. Laboratory observations showed that A. evonymellae is a solitary endoparasitoid of the poplar clearwing moth. It develops in early-stage (first- to fourth-instar) host larvae and overwinters as a larva in the host. Apanteles evonymellae is bivoltine, but only the second generation is associated with P. tabaniformis . In the field, adult parasitoids of first generation appear in April about 1 month before the emergence of P. tabaniformis . The longevity of A. evonymellae adults is a maximum of 6 days. Therefore, in the spring, A. evonymellae cannot attack neonate P. tabaniformis larvae and must develop in alternative hosts. Prior to their death the parasitized P. tabaniformis larvae construct conical structures, 'refuges' of frass and silk threads over the external openings of the larval galleries. Apanteles evonymellae pupates in these refuges after the host's death. This modified behaviour of the parasitized host larvae probably protects the pupae of A. evonymellae from hyperparasites and predators.     

Bioecological characteristics of Bassus tumidulus (Nees) (Hym., Braconidae), a parasitoid of the poplar twig borer, Gypsonoma aceriana (Dup.) (Lep., Tortricidae) in Bulgaria

Main aspects of biology and ecology of Bassus tumidulus (Nees), a parasitoid of Gypsonoma aceriana (Dup.), were studied during the period 1989–2000. Poplar tender shoots with G. aceriana larvae were collected at four localities in Bulgaria (Sofia, Svoge, Vardim and Pazardzhik) and examined in laboratory conditions. B. tumidulus was recovered in the Sofia and Svoge localities. It is a solitary internal parasitoid that attacks young larvae of G. aceriana (first–second instars) and kills host pre‐pupae. It develops two generations and overwinters as a larva in the host. Adult emergence of both overwintering and summer generation of B. tumidulus coincides with adult emergence of the host. In 1997, the first generation emergence of B. tumidulus was in relatively good synchrony with the first larval population of G. aceriana. However, the second generation B. tumidulus was not very well synchronized with the life cycle of G. aceriana because adult parasitoids appeared mostly in the beginning of the host larval population. The average mortality of G. aceriana, caused by this parasitoid in 1997 in Sofia, was 15.7 and 23.3% for the overwintering and summer generation, respectively. The highest level of parasitism by B. tumidulus, observed in individual study, was 61.5%, occurring during the summer generation in 1997.     

Lydella thompsoni Herting (Dipt., Tachinidae), a parasitoid of the European corn borer, Ostrinia nubilalis Hbn. (Lep., Pyralidae) in Slovakia, Czech Republic and south-western Poland

This paper shows that, within Central Europe, parasitism of the European corn borer (ECB) by the tachinid parasitoid, Lydella thompsoni (LT) increased from 0.47 to 1.49% in south-western Poland (51°03'N), to 4.31–21.95% in eastern Slovakia (48°20'N). The synchrony between the parasitoid LT and its primary host, the ECB, was studied in Central Europe under conditions where the host is univoltine, but the parasitoid is bivoltine. A cumulated total of more than 400 LT was field-collected from overwintering ECB larvae. The parasitoid hibernated as larva inside the host. Pupation started in the second half of the following March and 50% of pupation was surpassed in the first half of April. The first parasitoid adults emerged at the end of April and the majority at the beginning of May. Development threshold temperatures for 50% pupation was determined to be 2.7°C, and for 50% adult emergence 5.0°C; the respective thermal constants were 178.8–179.8 and 237.7–251.8 Celsius degree-days. Emerged adults did not parasitize overwintered ECB larvae in spring, hence there must be an alternate host for the first generation of LT in areas of univoltine life cycle of the ECB. Parasitization of the ECB larvae by LT continued until the end of July. The first parasitoid adults from this second generation emerged in the second half of August. By the end of the season, nearly one-third of LT adults had emerged. The rest of this generation apparently overwintered in the larval stage.     

Factors affecting the rate of attack by Cotesia rubecula (Hymenoptera: Braconidae)

Abstract. 1. The relationship between responses of the insect parasitoid Cotesia rubecula (Marshall) to kairomones produced by the feeding activities of its host, Pieris rapae (L.), and patterns of parasitism were investigated under field conditions.
2. Parasitoid adults aggregated in patches with the highest densities of host larvae but there was no commensurate increase in the rate of attack in these patches.
3. The rate of attack was not limited by the availability of eggs.
4. The rate of parasitoid attack was highest where feeding damage by the host was highest, irrespective of current host density.
5. The rate of parasitoid attack was further influenced by host age distribution. Late instar larvae were less susceptible to parasitism than were early instar larvae. The rate of attack on early instar larvae occupying the same plants as late instar larvae was reduced. This reduction in rate of attack was due to limitations on parasitoid search time imposed by the increased feeding damage associated with large host larvae and by the increased time the parasitoid required to recover from an attack on these large host larvae.     

中国钝唇姬蜂属三新种(膜翅目:姬蜂科)及二寄主新纪录(英文)

本文报道钝唇姬蜂属三新种乌钝唇姬蜂Eriborusfurvus,sp.nov.,沈阳钝唇姬蜂Eriborusshenyangensis,sp.nov.,柄钝唇姬蜂Eriborusstipitatus,sp.nov.和大螟瘦姬蜂E．terebrans（Gravenhorst）的二寄主新纪录,白杨透翅蛾ParanthrenetabaniformisRott.和青杨天牛SaperdapopulneaL．     

Interspecific competition between Diadegma semiclausum Hellen (Hym., Ichneumonidae) and Cotesia plutellae (Kurdjumov) (Hym., Braconidae) in parasitizing Plutella xylostella (L.) (Lep., Plutellidea)

Abstract:  Interspecific competition between Diadegma semiclausum and Cotesia plutellae was investigated at 25°C in the laboratory, by exposing the third instar larvae of the diamondback moth, Plutella xylostella to both species together, either species alone or by exposing the host larvae already parasitized by one species, at different intervals, to the other. When host larvae were exposed simultaneously to two species in one arena, parasitism rates of the host by each species were not reduced by the presence of the other species; joint parasitism rate by two species was not significantly higher than that by either parasitoid alone. Both parasitoids could lay eggs into the host larvae which had previously been parasitized by the other species, leading to the occurrence of multiparasitized hosts. When host larvae were parasitized first by D. semiclausum and then being followed within 1–2 h by exposing to C. plutellae , or vice versa, ensuing parasitoid cocoons from the multiparasitized host larvae were nearly all C. plutellae . When host larvae were parasitized initially by C. plutellae and then being followed by D. semiclausum two or more days later, all parasitoids ensued from the multiparasitized hosts were C. plutellae . In contrast, when host larvae were parasitized initially by D. semiclausum and then being followed by C. plutellae two or more days later, most host larvae could not survive to prepupae and most of the ensuing parasitoid adults from the surviving hosts were D. semiclausum . Dissections of host larvae at various time intervals after parasitization by the two parasitoids showed that development of both parasitoids in multiparasitized hosts were somewhat arrested, and that the first instar larvae of C. plutellae could initiate a physical attack on the larvae of D. semiclausum and remove the latter.     

Apple sawfly Hoplocampa testudinea (Hym., Tenthredinidae) and its parasitoid Lathrolestes ensator in Dutch apple orchards (Hym., Ichneumonidae, Ctenopelmatinae)

Abstract: Changes in population densities of the apple sawfly Hoplocampa testudinea (Klug) and its parasitoid Lathrolestes ensator (Brauns) were monitored in 15 apple orchards for a period of up to 4 years. The parasitoid species was found in all orchards except one, and was more numerous in plantings on sandier soils. Post‐bloom insecticide applications against other pests, and carbaryl for fruit thinning, often decimated both host and parasitoid in integrated pest management orchards. In organic orchards, where synthetic pesticides are banned, and Quassia is the only remedy against sawfly, the pest is more problematic. The low levels of parasitism in all organic orchards, except one, were possibly due to the application of wettable sulphur during the parasitoid flight period. The sawfly usually recovers more quickly than its parasitoid when chemical control is discontinued, because propagation of L. ensator is limited in various ways. The parasitoid is time limited, because suitable second instar host larvae are rarely available for more than a week on a single apple variety. Moreover, parasitism levels stay moderate because the parasitoid females do not avoid superparasitism. Finally, relatively more sawflies than parasitoids emerge after 10 months underground, because the incidence of prolonged diapause is more elevated in L. ensator than in the sawfly. It is suggested that both the high incidence of prolonged diapause and the inability to avoid superparasitism are useful in reducing the risk of local extinction. Elevated sawfly attack in a single early apple variety would reduce exploitation of suitable host larvae in other nearby varieties, in as far as the parasitoid is not able to distinguish fruitlets with accessible second instar host larvae from those with inaccessible older larvae. Although the former are available for a limited time, the latter may keep the parasitoids from moving to the less abundant second instar larvae in late(r) varieties. Reduction of elevated host density in such an early variety by a properly timed application of a short‐lived pesticide, such as Quassia, increases parasitism levels proportionally, and is expected to promote parasitoid movement to host larvae in other varieties nearby.     

Weak parasitoid-mediated apparent competition between two Phyllonorycter (Lepidoptera: Gracillariidae) leaf miner species on a deciduous oak Quercus dentata

Parasitoid assemblages and the rates of parasitism on tissue-feeding larvae of two Phyllonorycter leaf miner species, P. persimilis and P. leucocorona , were studied from the autumn generation in 2002 to the summer generation in 2005 to understand whether parasitoids mediate interactions between the two leaf miner species. Fourteen species of parasitoids emerged from P. persimilis and 11 emerged from P. leucocorona . The parasitism rate was high: 24.1–92.6% in P. persimilis and 58.9–81.7% in P. leucocorona . Thus, parasitism was a major mortality factor in the present Phyllonorycter species. The parasitoid composition was distinctly different between the two host species, although most parasitoids were able to parasitize both leaf miner species. The analysis based on the quantitative parasitoid overlap revealed that the present parasitoids could mediate interactions between the present leaf miner species, but their effects would be weak. This is attributable to parasitoid's preferential uses of either of the leaf miners as a host.     

六盘山翠金小蜂生物学特性的研究

六盘山翠金小蜂Tritneptis sp.是华北落叶松人工林主要食叶害虫落叶松红腹叶蜂Pristiphora erichsonii Hartig茧期的体外复寄生性天敌。对该蜂的生物学特性研究表明,该蜂在宁夏六盘山1年2代,以幼虫在寄主茧内越冬,翌年4月中旬开始活动取食,5月中旬开始化蛹,成蜂从6月中旬开始羽化,每头虫茧平均出蜂6.14头,雌雄比1.79∶1,雌蜂6月下旬开始产卵,一只雌蜂一生可在12.2头寄主虫茧上产卵,第1代寄生蜂幼虫7月上旬开始孵化并吸食寄主营养发育,7月下旬开始化蛹,8月上旬开始羽化并交尾、产卵寄生。该蜂体型较大,对寄主跟随性强,无重寄生天敌,自然寄生率7.3%～33.6%,是一种优良天敌寄生蜂。     

Recruitment of native parasitoids by an exotic leaf miner, Cameraria ohridella: host-parasitoid synchronization and influence of the environment

Abstract

• 1 The horse‐chestnut leaf miner, Cameraria ohridella, is a moth of unknown origin that has recently invaded Europe and severely defoliates the European horse‐chestnut, an important ornamental tree.
• 2 Several indigenous parasitoids have colonized this new host, but parasitism remains low. One of the hypotheses suggested to explain the low parasitism is that candidate parasitoids emerge too early in spring to attack the first host generation and, thus, need early‐occurring leaf miners as alternate hosts. This hypothesis was tested by observing the synchronization between the phenology of the moth and that of its main parasitoids, and by comparing parasitism rates and parasitoid richness in different environments with various levels of biological diversity.
• 3 In spring, the bulk of the parasitoids emerge at least 5 weeks before the occurrence of the first suitable larvae of C. ohridella whereas most parasitoid adults reared outdoors die within 5 weeks after emergence.
• 4 Parasitism rates and parasitoid richness do not increase with biological diversity, suggesting that most parasitoids attacking the first generation of C. ohridella do not come from alternate hosts. Parasitism does not increase later in the year in the subsequent generations, when host‐parasitoid synchronization becomes less critical.
• 5 We conclude that, although the spring emergence of parasitoids is not synchronized with the phenology of C. ohridella, the parasitoids attacking the first generation are probably old or late‐emerging adults of the overwintering generation. The lack of synchronization is probably not the only reason for the poor recruitment of native parasitoids by C. ohridella.

     

Mass-rearing biology of Fopius vandenboschi (Hym., Braconidae)

Abstract:   Basic biological information concerning the reproductive activities of Fopius ( Biosteres ) vandenboschi (Fullaway) (Hym., Braconidae, Opiinae) were determined to facilitate insectary mass production. Mean (±SE) progeny production per generation (yield) of 200 ♀♀ F. vandenboschi was 6835.8 ± 433.2 and 3755.8 ± 112.4 parasitoids, with 24-h exposure to second instar Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann), respectively. Ceratitis capitata as a factitious host was more sensitive to parasitism, producing a significantly higher percentage of uneclosed host puparia frequently containing parasitoid cadavers (22.5 ± 0.8%), than B. dorsalis (3.4 ± 0.2%). The overall mean production of female offspring was ≥50%♀♀ in both host species. Unlike several other opiine parasitoids, young (5-day-old) females of F. vandenboschi produced low proportion of daughters (26–37%♀♀) and significantly shifted production to female-biased offspring (53–71%♀♀) at older age intervals (16–30 days). Based on the parasitoid yield data with a 24-h exposure period to second instar host larvae of B. dorsalis , about 150 cage replicates (of 200 ♀♀ each) may be sufficient to mass produce about 1 million parasitoids of F. vandenboschi during the reproductive period of 5–30 days, with an average of 56% female offspring. A short oviposition exposure period of 6 h was not optimal for mass production of F. vandenboschi . Total yield at 6 h exposure was one-fifth the production at 24-h exposure, using B. dorsalis hosts.     

扬州地区水稻二化螟寄生蜂种类及主要寄生蜂发生动态

本文报道了江苏扬州地区水稻二化螟Chilo suppressalis(Walker)寄生蜂主要有10种,即中华钝唇姬蜂Eriborus sinicus(Holmgren)、二化螟盘绒茧蜂Cotesia chilonis(Munakata)、稻螟小腹茧蜂Microgaster russata Haliday、螟甲腹茧蜂Chelonus munakatae Munakata、中华茧蜂Amyosoma chinensis(Szepligeti)、螟黄足盘绒茧蜂Cotesia flavipes(Cameron)、夹色姬蜂Auberteterus alternecoloratus(Cushman)、桑蟥聚瘤姬蜂Iseropus(Gregopimpla)kuwanae(Viereck)、螟蛉瘤姬蜂Itoplectis naranyae(Ashmead)以及二化螟盘绒茧蜂的重寄生蜂绒茧灿金小蜂Trichomalopsis apanteloctena(Crawford)。田间系统调查表明:扬州地区7-9月水稻二化螟寄生蜂的主要种类为二化螟盘绒茧蜂、中华钝唇姬蜂、螟甲腹茧蜂、稻螟小腹茧蜂、螟蛉瘤姬蜂、桑蟥聚瘤姬蜂,但这些寄生蜂对一代水稻二化螟幼虫的寄生率较低,对二代水稻二化螟幼虫的寄生率高。水稻二化螟越冬期的系统调查表明:扬州地区二化螟越冬幼虫的寄生蜂主要有3种,即二化螟盘绒茧蜂、中华钝唇姬蜂和稻螟小腹茧蜂,其中二化螟盘绒茧蜂和中华钝唇姬蜂是寄生水稻二化螟越冬幼虫的优势种。水稻二化螟越冬幼虫的寄生率调查表明,扬州地区水稻二化螟越冬幼虫的寄生率在不同年份间有一定的波动,但一般都在15%以上,有的甚至高达89.88%,因此寄生蜂对二化螟越冬幼虫具有很好的控制作用,能有效压低来年水稻二化螟的田间越冬基数。此外,3种寄生蜂出茧时间在1月和2月之间达到最长,分别达到19.79 d、17.26 d和27.00 d,该结果表明,在扬州地区这3种寄生蜂可能都存在滞育现象。     

Life-cycle characteristics of Tetrastichus turionum, a parasitoid of the European pine shoot moth, Rhyacionia buoliana

Abstract:  The life cycle of Tetrastichus turionum , a pupal endoparasitoid of the European pine shoot moth Rhyacionia buoliana , was studied in Spain in the field, prior to its use as a potential biological control agent of this pest in Chile. T. turionum showed two generations acting on the same host generation. Adults from the overwintering generation emerged and dispersed from mid- to late spring and gave rise to a fast developing, current year generation. Adults of this generation emerged and oviposited in early to mid-summer, producing progeny that overwintered as fourth instar larvae inside their host. Both generations appeared highly synchronized to the presence of pupae in the host population. The role of decreasing day length in the induction of diapause is also discussed. Laboratory bioassays showed that T. turionum did not oviposit on R. buoliana larvae already parasitized by Orgilus obscurator , a major larval parasitoid, already introduced in Chile. The results reinforce the suitability of T. turionum as a promising parasitoid that would complement O. obscurator in the biological control of European pine shoot moth.     

Distribution, host specificity, and overwintering of Celatoria bosqi Blanchard (Diptera: Tachinidae), a South American parasitoid of Diabrotica spp. (Coleoptera: Chrysomelidae: Galerucinae)

The genus Diabrotica (Coleoptera: Chrysomelidae) includes a great number of pest species, including some of the most important crops pests of the Americas. However, only five parasitoid species have been recorded for it. The parasitoid Celatoria bosqi Blanchard was the first parasitoid described from Diabrotica spp. in South America, where substantial parasitism has been observed. C. bosqi has been collected almost throughout the South American distribution of its main host, Diabrotica speciosa (Germar), in an area that includes temperate and tropical lowlands, and semiarid to humid highlands. Three Diabrotica species were found to host the parasitoid, D. speciosa (Germar), Hystiopsis sp., and Diabrotica viridula (F.), with a total parasitism of 2.60, 5.55, and <0.02%, respectively. Laboratory experiments with field beetles and puparia, reared in the laboratory, indicate that C. bosqi overwinters obligatorily in overwintering adult host beetles, remaining quiescent in its live host below developmental temperatures. Based on the known climatic range of C. bosqi, and its requirement of adult overwintering hosts, a potential distribution in North America is projected.     

Bottom-up cascading effects in a tritrophic system: interactions between plant quality and host-parasitoid immune responses

Abstract.  1. Little is known about underlying mechanisms by which plants indirectly affect parasitism success in hymenopteran endoparasitoids. The hypothesis that host-plant effects can challenge the innate immune system of an insect host was experimentally tested in this study using a model tritrophic, crucifer – lepidopteran [ Plutella xylostella (L.)] – parasitoid [ Cotesia plutellae (Kurdjumov)], system.
2. The effects of host-plant suitability on herbivore performance and parasitism were examined. The bottom-up effect of plant suitability on host-parasitoid immune responses was then evaluated using measures of cellular and humoral effectors.
3. Host-plant quality showed a significant effect on the encapsulation response of P. xylostella to first instar but not to second instar parasitoid larvae. Encapsulation was never sufficient to prevent parasitoid emergence.
4. Poor host-plant suitability suppressed phenoloxidase activity in the absence of the parasitoid. The suppressive effect of C. plutellae on phenoloxidase activity was much greater and no plant effects were detectable after insects had been parasitized.
5. Despite strong plant effects on parasitism, those on immune effectors of the host were transitory or overwhelmed by the effect of the parasitoid.
6. These results demonstrated that plant-mediated variation in parasitism success by C. plutellae were not as a result of plant nutritional status or other attributes affecting the immune function of P. xylostella , nor to host-plant effects on superparasitism.
7. In these experiments, P. xylostella was a fully permissive host to C. plutellae and host-plant-mediated effects on the innate immune response appeared to play no part in parasitoid survival within hosts.     

Conflicts between a fungal entomopathogen, Zoophthora radicans, and two larval parasitoids of the diamondback moth

Zoophthora radicans (Zygomycetes: Entomophthorales), Diadegma semiclausum (Hymenoptera: Ichneumonidae), and Cotesia plutellae (Hymenoptera: Braconidae) are all natural enemies of the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae). Adult C. plutellae are not susceptible to Z. radicans infection but the pathogen can infect and kill adult D. semiclausum. Infection of adult D. semiclausum prior to exposure to P. xylostella host larvae significantly reduced the number of parasitoid cocoons subsequently developing from the host larvae. Although Z. radicans infection of P. xylostella larvae prior to parasitism by D. semiclausum or C. plutellae always resulted in the death of the immature parasitoids, neither species discriminated between healthy and Z. radicans-infected host larvae in an oviposition choice experiment. However, host larvae recently killed by Z. radicans were always rejected by D. semiclausum but sometimes accepted by C. plutellae. At 20 degrees C, egg to pupa development took 6.7 and 7.8 days for D. semiclausum and C. plutellae, respectively. C. plutellae parasitism significantly increased host instar duration but D. semiclausum parasitism did not. Cadavers of P. xylostella larvae parasitized 1 day prior to fungal infection showed no reduction in Z. radicans conidia yield. However, cadavers of larvae parasitized 3 days prior to fungal infection demonstrated a marked decrease in Z. radicans conidia yield. Z. radicans infection of P. xylostella larvae < or = 4 days after parasitism resulted in 100% parasitoid mortality; thereafter, the reduction in parasitoid cocoon yield decreased as the time between parasitism and initiation of fungal infection increased. The extended duration of the host larval stage induced by C. plutellae parasitism increased the availability of the parasitoid to the pathogen. Estimates of interspecific competition indicated a similar pattern for the interaction between Z. radicans and each species of parasitoid.     

闭弯尾姬蜂与菜蛾盘绒茧蜂寄生菜蛾幼虫时的种间竞争

在室内25℃下,以菜蛾3龄初幼虫作寄主,研究了菜蛾盘绒茧蜂Cotesia plutellae和半闭弯尾姬蜂Diadegma semiclausum的种间竞争。当寄主供2种蜂同时产卵寄生时,2种蜂各自的寄生率与其单独寄生时无显著差异,合计寄生率比一种蜂单独存在时有所提高,但差异不显著。2种蜂均能产卵寄生已被另一种蜂寄生了的寄主幼虫。当寄主被2种蜂寄生的间隔时间很短（少于10 h）时,所育出的蜂绝大部分（80%以上）为绒茧蜂;当寄主先被绒茧蜂寄生,并饲养2天以上再供弯尾姬蜂寄生时,所育出的全为绒茧蜂;当寄主先被弯尾姬蜂寄生,并饲养2天以上再供绒茧蜂寄生时,寄主幼虫绝大部分不能存活,只有少部分能育出寄生蜂,且多为弯尾姬蜂。当2种蜂的幼虫存在于同一寄主体内时,2种蜂的发育均受到另一种蜂的抑制;绒茧蜂1龄幼虫具有物理攻击能力,能将弯尾姬蜂卵或幼虫致死。这些结果表明,菜蛾盘绒茧蜂与半闭弯尾姬蜂在同一寄主中发育时,前者具有明显的竞争优势。     

斑痣悬茧蜂寄生、发育和生殖特征与寄主幼虫日龄的关系

【目的】“圆屋顶形”假说认为,对单寄生性姬蜂和茧蜂适合度而言,中间龄期幼虫寄主的品质高于更早和更晚龄期幼虫。该假说得到许多研究支持,但这些研究常以寄主幼虫脱皮划分虫龄,很少观测生殖特征,从而难以确切和全面描述适合度随寄主生长发育变化而变化的关系。本研究旨在检验“圆屋顶形”假说。【方法】本研究以斜纹夜蛾Spodoptera litura不同日龄幼虫为寄主,观测斑痣悬茧蜂Meteorus pulchricornis寄生和发育特征,并测定成蜂生殖力。【结果】线性回归分析表明,雌蜂对中间日龄寄主幼虫的寄生率大于对两端日龄寄主幼虫的寄生率;蜂卵至成虫的存活、成虫体型大小及其生殖力（产卵量）等适合度相关特征均表现出中间日龄寄主幼虫处理大于两端日龄幼虫处理。【结论】研究结果支持“圆屋顶形”假说。     

The reproductive strategy of the gregarious parasitoid,Pteromalus puparum (Hymenoptera: Pteromalidae)

Summary Pteromalus puparum is a gregarious parasitoid of lepidopterous pupae. To determine in which phase of a host outbreak superparasitism occurs, field investigations were carried out on seasonal prevalence of the host, Papilio xuhtus, and parasitism by P. puparum in a citrus grove in Fukuoka, Japan in 1974. Host pupation occurred from May to November and the parasitoid attacked the host throughout this period. Pupal density increased rapidly after mid-August and the percentage parasitism decreased during this period. A high level of parasitism was attained after one or more parasitoid generations in mid-September. The superparasitism was observed after mid-September when the parasitoid attained extremely high density, and resulted in an increase in the proportion of males, high mortality, and a decrease in the size of the progeny.     

Parasitism by Pteromalus cerealellae (Hymenoptera: Pteromalidae) on the Cowpea weevil, Callosbruchus maculatus (Coleoptera: Bruchidae): Host density, temperature effects, and host finding ability

Studies on interactions between a larval parasitoid, Pteromalus cerealellae (Boucek) and one of its hosts, Callosobruchus maculatus (F.) were carried out in the laboratory. The number of host larvae parasitized by P. cerealellae increased with host larvae at low densities and tended to a plateau at a density of 25 larvae per female parasitoid. Each parasitoid was able to parasitize more hosts and produced more offspring at 20 and 25 °C than at 30 °C. The number of non-infested seeds mixed with seeds infested with the last instar of C. maculatus did not preclude P. cerealellae from identifying infested seeds and attacking larvae inside them. When infested seeds were tightly packed, several host larvae escaped parasitism. P. cerealellae may be a useful biological control agent in newly harvested cowpea with low C. maculatus infestation, and lowering the temperature of the storage system may enhance the effectiveness of this parasitoid.