Effect of temperature on reproduction and parasitism of the egg parasitoid,Anastatus orientalis (Hymenoptera: Eupelmidae)

Anastatus orientalis is a solitary endoparasitoid of Lycorma delicatula (Hemiptera: Fulgoridae) eggs. We investigated the development, longevity, fecundity, and sex ratio of A. orientalis on different temperatures to establish the optimal temperature condition for laboratory mass rearing. There were significant differences in its development and longevity between 15 °C and the rest of temperature conditions (20, 25, and 30 °C), among which were no significant differences. The average number of eggs laid by A. orientalis was higher at 20 and 25 °C, but there was no statistically significant difference in its fecundity between the two temperatures. More females emerged at 15 and 20 °C than higher temperatures.Parasitisms of A. orientalis varied with host egg ages and densities. Even in 14 day old eggs of L. delicatula, parasitoids successfully emerged from 92.3% of the parasitized eggs. On the other hand, parasitism was lowest (13.8%) on just before hatching eggs. Parasitism was negatively dependent on host density.Oviposition behavior for A. orientalis primarily occurred at 1400–1600 h, not at 2400–0800 h. The majority of this parasitoid's emergence occurred at 0800–1000 h, largely before noon. These results may be useful for controlling the adequate time for supplying host eggs and release density of this parasitoid as well as for potentially predicting the accurate time for securing parasitoid adults in laboratory mass rearing of A. orientalis.     

Biological studies on Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae), egg parasitoid of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae)

The tomato moth, Tuta absoluta Meyrick, is one of the most important tomato pests in South America. In Argentina, management strategies include only chemical control. In this work, the parasitoid wasp Trichogrammatoidea bactrae Nagaraja was evaluated as a potential natural enemy against this pest. Biological and population parameters were estimated by developing a life table under laboratory conditions at 25 ± 1oC, 14:10 photoperiod and 60 ± 10% RH. Three cohorts of 26-30 T. bactrae females each were placed with one of the three following treatments: 1 - Sitotroga cerealella (Olivier) eggs on a piece of cardboard; 2 - S. cerealella eggs on a piece of tomato leaf, and 3- T. absoluta eggs on a piece on tomato leaf. The following parameters were estimated for each cohort: survival (egg to adult), longevity, fecundity and oviposition period of females, sex proportion of the F1, net rate of reproduction (Ro), mean generation time (T) and intrinsic rate of population increase (r m). Survival of the T. bactrae immatures was higher than 90% on both, S. cerealella and T. absoluta eggs. The female survival curves corresponded to type III and showed no significant differences among treatments. The three cohorts did not show significant differences between sex ratio, female longevity, oviposition period, fecundity and the population parameters studied. These results indicate that T. bactrae would be a potential biological control agent of T. absoluta.     

繁育寄主对三种赤眼蜂个体大小及抱卵量的影响

【目的】繁育寄主及成蜂日龄均会影响赤眼蜂体内的抱卵量,为了解繁育寄主及育出赤眼蜂个体大小与赤眼蜂抱卵量的关系,我们在室内研究了米蛾 Corcyra cephalonica（Stainton）卵和亚洲玉米螟 Ostrinia furnacalis （Güenée）卵作为繁育寄主对3种赤眼蜂雌蜂大小、抱卵量的影响。【方法】在光周期14L:10D、温度25±1℃的室内条件下,以米蛾卵、亚洲玉米螟卵作为繁育寄主,解剖不同日龄（羽化后12-72 h）松毛虫赤眼蜂 Trichogramma dendrolimi Matsumura、玉米螟赤眼蜂Trichogramma ostriniae Pang et Chen以及稻螟赤眼蜂Trichogramma japonicum Ashmead,观察雌蜂抱卵量,测量成蜂的大小,分析雌蜂抱卵量与其日龄、个体大小以及繁育寄主的关系【结果】在羽化后48 h以内,3种蜂的抱卵量随雌蜂日龄的增长而增加。羽化后72 h,除米蛾卵繁育的玉米螟赤眼蜂及玉米螟卵繁育的松毛虫赤眼蜂的抱卵量比羽化后48 h时略高外,其他组合均出现下降。以亚洲玉米螟卵为繁育寄主时的玉米螟赤眼蜂的抱卵量显著高于对应日龄的以米蛾卵为繁育寄主时的抱卵量,而松毛虫赤眼蜂（除羽化后12和24 h外）和稻螟赤眼蜂则相反;以米蛾卵为繁育寄主时,相同日龄的赤眼蜂中,松毛虫赤眼蜂抱卵量最高,稻螟赤眼蜂的抱卵量最低;以亚洲玉米螟卵为繁育寄主时,玉米螟赤眼蜂抱卵量最高,稻螟赤眼蜂抱卵量最低。雌蜂抱卵量与雌蜂个体大小呈线性正相关,相关程度随雌蜂日龄增加而更加明显。【结论】后足胫节长度可以作为评价松毛虫赤眼蜂、玉米螟赤眼蜂和稻螟赤眼蜂质量的指标。赤眼蜂抱卵量受繁育寄主、赤眼蜂蜂种及雌蜂日龄的显著影响,寄主的适合性也会影响育出赤眼蜂的大小,筛选合适的繁育寄主有助于提高赤眼蜂的质量。     

Performance of Trichogrammatoidea sp. nr lutea Girault (Hymenoptera: Trichogrammatidae) collected from Mussidia spp. in Kenya on eggs of six lepidopteran hosts

Mussidia nigrivenella Ragonot (Lepidoptera: Pyralidae), an important pest of maize ears in West Africa, has never been reported to attack crops in East and southern Africa (ESA), though it was found on various wild host plants in these regions. It was suggested that in ESA M. nigrivenella might be under natural control. In Kenya, exploration for natural enemies associated with Mussidia spp. yielded several parasitoids including a trichogrammatid egg parasitoid, Trichogrammatoidea sp. nr lutea Girault. The ability of T. sp. nr lutea to attack the eggs of several lepidopteran species found in Kenya was studied. The lepidopterans included the noctuids Busseola fusca (Fuller) and Sesamia calamistis (Hampson), the pyralids Eldana saccharina Walker, Mussidia fiorii Cecconi and de Joannis and Mussidia‘madagascariensis’, and the crambid Chilo partellus (Swinhoe). The former three species also infest cereals in West Africa. Trichogrammatoidea sp. nr lutea successfully attacked and developed in eggs of all six species indicating its potential to exploit other lepidopteran pests of maize in West Africa. Busseola fusca and S. calamistis were the most suitable hosts and had the largest number of eggs parasitized and progeny per female wasp where E. saccharina and C. partellus were the poorest hosts. The host species used to rear the parasitoid and the age of egg also significantly affected the total number of host eggs parasitized by the parasitoid. It was concluded that the ability of T. sp. nr lutea to exploit lepidopterans that are also pests of maize in West Africa may enhance biological control of M. nigrivenella and it should be considered for translocation to that area from Kenya.     

Strategic ejaculation in the egg parasitoid Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

Abstract.  1. Several parameters influence sperm allocation by males, including their size and sperm stock, intra-specific variability, quality of females', as well as the risk and intensity of sperm competition.
2. Models predict that males should invest the maximum ejaculate size when sperm competition intensity is low. As sperm competition intensity increases, males should decrease the number of sperm transferred during mating.
3. This decrease in sperm transfer to females occurs because the benefits gained by males with each extra unit of expenditure on sperm decrease. When sperm supply is not unlimited, males could expect a better return by keeping some or all sperm for mating under lower competition intensity.
4. In this study, the ejaculate size of males that were kept in groups of one, five or 10 males prior to mating, has been investigated in the haplodiploid egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae).
5. As predicted by theory, the number of sperm transferred decreased significantly with an increase in the number of rivals.
6. This is the first study showing strategic sperm allocation depending on sperm competition intensity in a parasitoid.     

Scope for genetic enhancement of the parasitisation potential of four native strains of Trichogrammatoidea sp. nr. lutea Girault (Hymenoptera: Trichogrammatidae) in Kenya

In response to emerging interest in commercial mass production of Trichogramma for Helicoverpa armigera biocontrol in eastern Africa, laboratory experiments were undertaken to assess the scope for genetic enhancement of the parasitisation potential of native strains of the local common trichogrammatid species, Trichogrammatoidea sp. nr. lutea. Four promising strains (ex-Kilifi – Kilifi District, ex-Kwa Chai – Kibwezi District, ex-Rarieda – Bondo District and ex-Ebuhayi, Kakamega District) were tested for cross-mating in reciprocal combinations with focus on fecundity and progeny female ratio. While all the crosses resulted in F1 progeny of both sexes, significant differences were observed between homogamic and reciprocal heterogamic crosses in fecundity, progeny production, proportion of female progeny and adult longevity. Among all the crosses, the cross between ex-Rarieda strain females and ex-Kilifi strain males resulted in progeny that was significantly superior in fecundity and progeny female ratio. Conversely, Kilifi strain females crossed to males from ex-Rarieda strain gave rise to progeny with relatively low fecundity and female ratio. There were significant differences between homogamic crosses and most reciprocal heterogamic crosses in the major biological attributes. Genotypic and phenotypic variance-covariance matrices generated for six life-history traits showed high positive correlations for most traits in both inbred (P<0.05) and reciprocal heterogamic crosses (P<0.05 and P<0.001). Fecundity and number of female offspring were the most important factors in the heterogamic crosses. The results confirmed the scope for genetic enhancement through inter-strain crossing for improving the field impact potential of T. sp. nr. lutea being targeted for commercial mass production.     

Effect of host quality of Callosobruchus maculatus (Coleoptera: Bruchidae) on performance of the egg parasitoid Uscana lariophaga (Hymenoptera: Trichogrammatidae)

Development and reproductive success of the solitary egg parasitoid Uscana lariophaga Steffan were examined after development in eggs of the bruchid storage pest Callosobruchus maculatus Fabricius reared at either low or high densities on cowpea seeds and laid at day 1 and 4 of maternal life. Both bruchid larval competition and maternal age negatively affected egg size, but the latter more than the former. Uscana lariophaga reared in small hosts developed slower, were smaller and produced fewer eggs compared to parasitoids reared in large hosts. Fecundity of the parasitoid was heavily influenced by host egg size. This was reflected in the values for the intrinsic rate of increase of U. lariophaga, which differed for wasps that developed in host eggs laid by bruchid females of different age. Wasps allocated marginally more female offspring to larger hosts.     

Developmental time,longevity, reproductive capacity and sex ratio of the mealybug parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

Key biological parameters of Anagyrus sp. nr. pseudococci reared on the citrus mealybug Planococcus citri (Risso) were determined. The mean longevity of female wasps was 21.1 days, the median lethal time (LT₅₀) was 22 days, the mean number of offspring per female was 30.2 wasps and the sex ratio of the progeny was slightly male biased (1.1 males per female). Wasps fed with water showed a significantly lower longevity compared to that recorded for wasps fed with syrup for bee nutrition mixed with water. The longevity of female wasps was significantly higher compared to males when the syrup-water solution was provided as food. Longevity was significantly higher for female wasps fed with syrup and water in comparison with those exposed to host mealybugs. The mean development time of female and male wasps was 14.7±0.1 and 14.5±0.1 days, respectively.     

Differences in egg parasitism of Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae) by Enoggera nassaui Girault (Hymenoptera: Pteromalidae) in relation to host and parasitoid origin

Abstract The first instances of egg parasitism of Chrysophtharta agricola , a pest of eucalypt plantations, are recorded. Enoggera nassaui was found parasitising C. agricola egg batches in Tasmania, the Australian Capital Territory (ACT), New South Wales and Victoria: this is the first record of this parasitoid species from Victoria. One instance of Neopolycystus sp. parasitising C. agricola eggs in Victoria was also recorded. Parasitism of egg batches by E. nassaui ranged from 0 to 55% between five geographical populations collected in mainland Australia ( n  = 45), and from 0 to 2% between two populations collected in Tasmania ( n  = 300). For mainland sites at which parasitism was recorded, parasitism rates within sites differed significantly from either population in Tasmania. Reciprocal exposure experiments using one Tasmanian (Florentine Valley) and one parasitised mainland (Picadilly Circus, ACT) population were conducted in the laboratory to examine whether these different parasitism rates were attributable to egg or parasitoid origin. Parasitoids from the ACT parasitised C. agricola eggs of both origins more successfully than parasitoids from Tasmania, with up to 65% wasp emergence compared with 33% from Tasmania. Parasitoid origin significantly affected the number of wasps that emerged from exposed batches, but not the total loss from parasitism.     

Factors affecting parasitism by Microctonus aethiopoides (Hymenoptera: Braconidae) and parasitoid development in natural and novel host species

A laboratory study of aspects of parasitoid host acceptance, suitability and physiological regulation in natural and novel host species was carried out to investigate the degree of variability encountered with different hosts and to determine the value of such observations in host range determination. The parasitoid Microctonus aethiopoides Loan was exposed to a natural host, Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) and three novel hosts, the New Zealand native Nicaeana cervina Broun, the introduced weed biological control agent Rhinocyllus conicus (Froehlich), and a congeneric pest species, Sitona lepidus Gyllenhal (all Coleoptera: Curculionidae). Per cent parasitism of these species was 54%, 43%, 39% and 0%, respectively. The results indicated that for both S. discoideus and R. conicus more males than females were parasitized (69% cf. 45%, and 49% cf. 32% respectively) but host size was not a significant factor. Overall, superparasitism was recorded in about 29% of parasitized weevils and there was evidence that host discrimination to avoid superparasitism occurred in the natural host. Conversely, superparasitism occurred more frequently than would be expected in N. cervina (42%) coupled with higher survival of larvae in superparasitized hosts in this species. The frequency distribution of attack of R. conicus by M. aethiopoides was not different from random. Parasitoid development was more rapid in the natural host, S. discoideus, and parasitoid size was positively correlated with host size. There was a strong positive relationship between parasitoid larval survival and the presence of teratocytes in all hosts. Host fecundity and fertility were reduced by parasitism for most species, and in some cases, by exposure to parasitoids in the absence of detectable parasitism. It was concluded that laboratory observations can provide useful information on the compatibility between host and parasitoid which can complement traditional host range tests to predict field host range.     

Biological studies on two neotropical egg parasitoid species: Trichogramma nerudai and Trichogramma sp. (Hymenoptera: Trichogrammatidae)

The main biological attributes of two Neotropical egg parasitoids, the arrhenotokous Trichogramma nerudai and the thelytokous Trichogramma sp., were assessed under controlled laboratory conditions. Developmental time from egg to adult, and parasitoid survival, fecundity and fertility were studied using life tables. Results showed that T. nerudai had a faster developmental time than Trichogramma sp. (13.014±0.4019 and 13.595±0.4931 days, respectively). Both species showed similar life table statistics, r_m was 0.222 and 0.225 for T. nerudai and Trichogramma sp., respectively. Parasitoid survival averaged 95% for both species. The results obtained are discussed in the context of selecting one of these natural enemies as a potential biological control agent for the European pine shoot moth Rhyacionia buoliana (Lepidoptera: Tortricidae) in pine forests and the codling moth Cydia pomonella (Lepidoptera: Tortricidae) in apple orchards in Argentina.     

Effects of various insecticides on the development of the egg parasitoid Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae).

The toxicity of six insecticides, acephate, methomyl, ethofenprox, cartap, chlorfluazuron, and Bacillus thuringiensis (Bt) was tested on different developmental stages of the egg parasitoid, Trichogramma dendrolimi (Matsumura). Each of the insecticides tested showed different degrees of toxicity to the parasitoid, Ethofenprox showed the highest toxicity and cartap showed relatively higher toxicity compared with the other insecticides. The development of the parasitoids treated with these two insecticides was normal, similar to that of the control group. Only the emergence of adult wasps from host eggs was disturbed. Emergence of the host, Mamestra brassicae larva was reduced following treatment with ethofenprox, cartap and methomyl. However, adult female wasps, which emerged from host eggs treated with the insecticides had the ability to oviposit normally.     

Effect of host egg viability on reproduction and development of Trichogramma cacoeciae and T. principium (Hymenoptera: Trichogrammatidae)

A combination of a sterile insect technique, resulting in infertile eggs, and of an egg parasitoid, should provide better control of codling moth than either alone. Non-choice laboratory experiments were conducted with infertile and fertile codling moth eggs to evaluate the potential parasitism and reproduction of Trichogramma cacoeciae Marchal and T. principium Sug. et Sor. The tendency of T. cacoeciae females to attack infertile eggs was similar to that for fertile eggs, whereas T. principium showed a greater preference for infertile eggs than fertile eggs. The fertility status of the host did not affect the number of eggs that were parasitized but fewer F₁ progeny emerged from infertile eggs when parasitized than from fertile eggs. When T. cacoeciae and T. principium parasitized infertile host eggs their mean developmental time was prolonged but the viability and quality of parasitoid progeny was not influenced by the fertility status of the host eggs. The study demonstrates the compatibility of use of T. cacoeciae and T. principium in an integrated program employing the sterile insect technique for codling moth management.     

新疆光脉赤眼蜂属种类记述(膜翅目:赤眼蜂科)

本文简述了光脉赤眼蜂属Aphelinoidea Girault的研究历史及现状,并描述了采自新疆的光脉赤眼蜂属3个种,其中有1新种,2中国新记录种,同时提供了新疆光脉赤眼蜂属分种的分类检索表,另附主要形态特征图。所有标本保存在福建农林大学生物防治研究所。1．长翅光脉赤眼蜂Aphelinoidea dolichoptera (Novicky),中国新记录(图1)Aphelinoidea dolichoptera(Novicky),1933,Polsk.Pismo Ent.12:4。观察标本：1♀,2♂♂,新疆新源县,2001-Ⅵ-01,吴卫网扫;1♂,新疆乌鲁木齐市,2001-Ⅶ-25,崔卫东网扫。2．沙湾光脉赤眼蜂Aphelinoidea shawanica,新种(图2)本种与Aphelinoidea subexserta Novicky很相似,但本种前翅的缘毛较长,翅面纤毛较稀少;产卵管明显露出：触角棒节基部深褐色,端部淡黄色。正模：♀,新疆沙湾县,2001-Ⅶ-14,胡红英网扫;副模：1♀,同正模;2♀♀,新疆温泉县,2001Ⅶ-16,胡红英网扫;2♀♀,石河子市150团,2001-Ⅶ-12,胡红英网扫。3．土耳其光脉赤眼蜂Aphelinoidea anatolica Novicky,中国新记录(图3)Aphelinoidea natolica Novicky,1936,Zeit．Angew.Ent．Berlin．23：144．观察标本：2♀♀,1♂,新疆沙湾县,2001-Ⅶ-14,胡红英网扫;1♀,新疆温泉县,2001-Ⅶ-12,胡红英网扫;1♀,石河子市150团,2001-Ⅶ-12,胡红英网扫;4♀♀,3♂♂,新疆新源县,2001-Ⅶ-01,吴卫网扫;1♀,新疆呼图壁县,1999-Ⅷ-27,林乃铨网扫;1♂,新疆五家渠市,2001-Ⅶ-26,孙涛网扫;1♂,新疆和静县,2001-Ⅷ-08,胡红英网扫。2♀♀,新疆和硕县,2001-Ⅷ-07,胡红英网扫;3♀♀,3♂♂,新疆博湖县,2001-Ⅷ-07,胡红英网扫。     

Development of Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) in Helicoverpa (Lepidoptera: Noctuidae) host eggs

Abstract Morphological studies of development of the egg parasitoid Trichogramma australicum Girault in the cotton bollworm, Helicoverpa armigera (Hübner), were conducted to provide benchmarks for assessing developmental rates in both natural hosts and artificial diets. Observations of living embryos and histological sections show that embryos proceed rapidly through cleavage and blastoderm formation and show a characteristic pinching or rotation 8 h after deposition. Eggs progressively increase in volume, primarily by increasing in diameter at the widest point. At 29 ± 1°C the duration of the egg stage is 22−24 h, the larval stage 27 h, the prepupal stage 50−52 h, and pupa 85 h. Larvae undergo dramatic shape changes as they ingest food but do not show signs of larval moults, reinforcing observations that there is only one larval instar. Criteria for staging the embryonic and postembryonic development in natural hosts will be used for future studies aimed at developing and refining artificial diets for Trichogramma.     

卷蛾分索赤眼蜂雌蜂的颜色偏好性

为了确定卷蛾分索赤眼蜂Trichogrammatoidea bactrae Nagaraja 雌蜂的颜色偏好性, 在室内通过在培养皿底部黏贴彩纸的方法测定卷蛾分索赤眼蜂雌蜂对红、 黄、 黑、 紫、 绿、 白、 蓝7种颜色的行为趋性反应。结果表明, 卷蛾分索赤眼蜂雌蜂在红、 黄、 紫、 绿和蓝5种颜色上的滞留时间都极显著地高于对照（P<0.01）, 在黑和白2种颜色上的滞留时间与对照没有显著差异（P>0.05）; 对黄色的首次选择率极显著高于对照(P< 0.01), 对红、 紫、 绿和蓝色的首次选择率均显著高于对照(P＜0.05), 对黑色和白色的首次选择率与对照没有显著差异。当雌蜂分别在黄与红、 紫、 绿和蓝两两颜色之间选择时, 雌蜂在黄色彩纸上的滞留时间显著长于其他4种颜色。当雌蜂对红、 紫、 绿、 蓝和黄色5种颜色一起选择时, 在首次选择率、 滞留次数上5种颜色间都没有明显差异(P＞0.05); 但在红色和蓝色上的滞留时间显著长于紫色(P＜0.05), 在这3种颜色上的滞留时间与在黄色和绿色上的滞留时间均无显著差异(P＞0.05)。卷蛾分索赤眼蜂雌蜂在7种颜色卵卡上分别与透明纸（对照）上的米蛾卵的选择寄生时, 在黄色卵卡上的寄生卵量极显著多于对照(P＜0.01), 黑色卵卡上的寄生卵量极显著少于对照(P＜0.01), 其他5种颜色的卵卡上的寄生卵量与对照没有显著差异(P＞0.05)。结果说明, 卷蛾分索赤眼蜂雌蜂对黄色最为偏好, 其次偏好红、 紫、 绿和蓝色, 较不喜好白色和黑色。     

Costs and benefits of polyandry in the egg parasitoid Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae)

Polyandry implies costs (i.e., time, energy, predation risk, etc.) especially in short-lived parasitoid species but females of several hymenopteran parasitoid species, mostly gregarious, do mate with multiple males. Several hypotheses have been proposed to explain the benefits of polyandry but controversy remains, especially in facultative gregarious species that bridge the gap between solitary and gregarious development. In this study, we investigated the possibility that polyandry may bring material benefits to Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) females, a short-lived and facultative gregarious egg parasitoid. Females mated several times with different males both at emergence and throughout their life. No significant difference was found in the offspring sex ratio and the fecundity of multiple mated and single mated females and pre-mating duration increased with the female’s age. The longevity of females did vary significantly with the number of matings but only in the presence of hosts. Female T. evanescens received enough sperm from one mating to allocate an optimal offspring sex ratio and we found no evidence of either nutritional resources or convenience polyandry in this species. Polyandry in facultative gregarious parasitoids might be an adaptive strategy to minimize the risk of mating with males that have already emptied their sperm bank or to accumulate sperm from several partially sperm-depleted males. Polyandry may also increase the probability of non-sib mating in patches exploited by several females.     

Taxonomic study of Ufens Girault from Xinjiang,China(Hymenoptera: Trichogrammatidae)

The genus Ufens Girault(Hymenoptera: Trichogrammatidae) is reported from Xinjiang, including one newly recorded species for China, U. pallidus Owen, and U. foersteri(Kryger), U. similis(Kryger). Ufensia xinjiangensis Hu Lin is synonymized under U. foersteri. A key to males of six species of Ufens from China is provided. All the specimens examined are deposited in the Insect Collection of College of Life Science and Technology, Xinjiang University, Urumqi, Xinjiang, China(ICXU).     

Effects of host species, stage and size on the sex ratio and clutch size of the parasitoid, Dibrachys boarmiae (Walker, 1863) (Hymenoptera: Pteromalidae)

Effects of host species, stage and size on clutch size and sex ratio of the gregarious, idiobiont ectoparasitoid Dibrachys boarmiae were investigated at 25±2°C and 70±5% relative humidity. The greater wax moth, Galleria mellonella, small wax moth, Achroia grisella, and early stage solitary larvae of the endoparasitoid, Apanteles galleriae, were used as hosts. Clutch size was greatest from prepupae of the largest host, Galleria mellonella, with a mean of 40.07 offspring per host versus 14.73 and 2.93 for Achroia grisella and Apanteles galleriae, respectively. The mean clutch size from pupae was lower than from prepupae, being 17.27, 10.73 and 2.89 for Galleria mellonella, Achroia grisella and Apanteles galleriae, respectively. Within each host species and stage, heavier hosts resulted in larger clutches. The sex ratio of offspring (proportion of male) was approximately 0.20, with only minor differences among host species, stages and sizes.     

Effect of temperature on parasitism and host-feeding of Trichogramma turkestanica (Hymenoptera: Trichogrammatidae) on Ephestia kuehniella (Lepidoptera: Pyralidae)

The egg parasitoid Trichogramma turkestanica Meyer is being evaluated as a biological control agent against the Mediterranean flour moth, Ephestia kuehniella Zeller, in flour mills. The longevity, parasitism and host-feeding of the parasitoid at four constant temperatures (15-30 degrees C) has been determined in the laboratory. The highest fecundity occurred at intermediate temperatures. The number of host eggs killed by host-feeding per female was highest at the two lower temperatures. A very conservative estimate of host-feeding showed that it accounts for approximately half of the mortality of host eggs at 20 and 25 degrees C and thus could constitute a major mortality factor for the flour moth population.