Oviposition behaviour, influence of experience on host size selection, and niche overlap of the solitary Leptomastix epona and the gregarious Pseudaphycus flavidulus, two endoparasitoids of the mealybug Pseudococcus viburni

Oviposition behaviour and host size selection of the solitary parasitoid Leptomastix epona(Walker) and the gregarious Pseudaphycus flavidulus(Brèthes) [both Hymenoptera: Encyrtidae] were examined on five size classes of the mealybug Pseudococcus viburni(Signoret) [Hemiptera: Pseudococcidae]. The host size classes mostly consisted of one stage (first, second, third instar nymph, young adult and preovipositing adult) and were presented together to wasps of either parasitoid species. Both parasitoid species locate the host by drumming the surface of the patch with the antennae. Leptomastix eponaseems to use mainly the antennae to examine the host but P. flavidulusmay accept or reject a host for oviposition after antennation or insertion of the ovipositor. Leptomastix eponaattempts oviposition in all the host stages from second instar nymphs but P. flavidulusincludes first instar. Both parasitoid species select mainly larger hosts (>1 mm, third instar nymphs) to oviposit but P. flavidulusis able to parasitize more second instar nymphs compared to L. epona. Female wasps of L. eponamay host feed on small mealybugs (second and third instar nymphs) that they do not use for oviposition. Oviposition experience of either parasitoid species for 24 hours does not influence host size selection on patches with hosts of similar mixed sizes. Oviposition decisions are independent of the host sizes of the preceding ovipositions. Implications about stability of a single parasitoid – host system and the success of biological control of the mealybug were discussed in respect of the developmental refugia of the two parasitoid species. Niche overlap of the two parasitoid species was discussed with a view to giving an insight into a single or multiple introduction.     

Superparasitism in Cotesia glomerata: response of hosts and consequences for parasitoids

Abstract.  1. Superparasitism occurs in Cotesia glomerata (Hymenoptera: Braconidae), a gregarious endoparasitoid of Pieris spp. (Lepidoptera: Pieridae). The response of P. brassicae larvae to superparasitism and the consequences for the parasitoid were examined in order to elucidate the ecological significance of this behaviour.
2. Field surveys of a Swiss population revealed that C. glomerata brood sizes from P. brassicae larvae ranged from three to 158, and both the female ratio and the body weight of emergent wasps correlated negatively with brood size. In the laboratory, single oviposition on P. brassicae larvae did not produce any brood size larger than 62, but brood size increased with superparasitism.
3. Laboratory experiments demonstrated that both naive and experienced female wasps were willing to attack hosts that had been newly parasitised by themselves or conspecifics. Superparasitism reduced survivorship but increased food consumption and weight growth in P. brassicae larvae. Superparasitism lengthened parasitoid development and prolonged the feeding period of host larvae.
4. Despite a trade-off between maximising brood size and optimising the fitness of individual offspring, two or three ovipositions on P. brassicae larvae resulted in a greater dry female mass than did a single oviposition on the host. Thus, superparasitism might be of adaptive significance under certain circumstances, especially when host density is low and unparasitised hosts are rare in a habitat.     

BIONOMICS OF MICROPLITIS MEDIATOR (HYM: BRACONIDAE) PARASITIZING PSEUDALETIA SEPARATA (LEP: NOCTUIDAE)*

Abstract This paper deals with the bionomics of Microplitis mediator parasitizing Pseudaletia separata. There were some stings (ca. 3. 1%) in which female wasps oviposited more than one eggs and about 4. 6% stings that there was no egg laid into a host. A negative correlation existed between the host age and percentage of parasitization. When the host suffered more stings by the parasitoid wasps, the percentage of parasitization was higher. But there was no correlation between the parasitoid sex ratio and the host age or the frequency of stings by the parasitoids. The host age is not the major factor affecting the offspring sex ratio of the parasitoid. Some putative sex determinant factors in the parasitoid are discussed and the 2nd instar of the host is recommended as a suitable host age in which parasitization could be performed for the purpose of the parasitoid mass culture.     

Influence of aphid size,age and behaviour on host choice by the parasitoid wasp Ephedrus californicus: a test of host-size models

Summary When host quality varies, parasitoid wasps are expected to oviposit selectively in high-quality hosts. We tested the assumption underlying host-size models that, for solitary species of wasps, quality is based on host size. Using Ephedrus californicus, a solitary endoparasitoid of the pea aphid, we evaluated the influence of aphid size (= mass), age and defensive behaviours on host selection. Experienced parasitoid females were given a choice among three classes of 5-day-old apterous nymphs: small aphids that had been starved daily for 4 h (S4) and 6 h (S6) respectively, and large aphids permitted to feed (F) normally. Wasps attacked more, and laid more eggs in, small than large aphids (S6>S4>F). This rank-order for attack did not change when females could choose among aphids of the same size that differed in age; however, wasps oviposited in all attacked aphids with equal probability. Host size did not influence parasitoid attack rates when aphids were anaesthetized so that they could not escape or defend themselves. As predicted by host-size models, wasp size increased with host size (F>S4; S6), but large wasps required longer to complete development than their smaller counterparts (S4E. californicus reflects a trade-off between maximization of fitness gains per egg and the economics of search-time allocation. Because large aphids are more likely to escape parasitization, a wasp must balance her potential gain in fitness by ovipositinng in a high-quality (large) aphid against her potential cost in terms of lost opportunity time if the attack fails.     

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。     

Interspecific competition between the braconid endoparasitoids Glyptapanteles porthetriae and Glyptapanteles liparidis in Lymantria dispar larvae

The effect of interspecific competition between the solitary endoparasitoid Glyptapanteles porthetriae Muesebeck (Hymenoptera: Braconidae) and the gregarious Glyptapanteles liparidis Bouché (Hymenoptera: Braconidae), was investigated in larvae of Lymantria dispar L. (Lepidoptera: Lymantriidae). Host larvae were parasitized by both wasp species simultaneously in premolt to the 2^nd or the 3^rd host instar or in an additional approach with a 4-day delay in parasitization by the second wasp species. Host acceptance experiments revealed that both wasp species do not discriminate between unparasitized host larvae and larvae parasitized previously by the same or the other species. In more than 90% female wasps parasitized the larva they encountered first. During the period of endoparasitic development, larvae of the competing parasitoid species never attacked the egg stage of the other species. When host larvae were parasitized simultaneously by both wasp species, the rate of successful development of both species depended on the age of the host larva at the time of its parasitization; G. liparidis emerged successfully from 44% of host larvae parasitized during the premolt to 2^nd instar, G. porthetriae from 28%, and in 20% of the hosts both parasitoid species were able to develop in one gypsy moth larva. However, when host larvae were parasitized simultaneously during premolt to the 3^rd instar, G. liparidis was successful in 90% of the hosts, compared to 8% from which only G. porthetriae emerged. In the experiments with delayed oviposition, generally the species that oviposited first succeeded in completing its larval development. Larvae of the species ovipositing with four days delay were frequently attacked and killed by larvae of the first parasitizing species or suffered reduced growth. As the secondary parasitoid species, G. porthetriae-larvae were never able to complete their development, whereas G. liparidis developed successfully in at least 12,5% of the multiparasitized host larvae. Thus, multiparasitism of gypsy moth larvae by both Glyptapanteles species corresponds to the contest type; however, G. porthetriae is only able to develop successfully as the primary parasitoid of young host larvae.     

寄主大小及寄生顺序对蝇蛹佣小蜂寄生策略的影响

寄主大小模型认为寄生蜂后代性比与寄主大小相关,寄生蜂倾向于在大寄主上产出更多雌性后代,在小寄主上产出更多雄性后代.探讨了以家蝇蛹为寄主时,蝇蛹佣小蜂后代产量和性比变化;单次寄生情况下,寄主大小及寄生顺序对寄生蜂后代性比等影响.结果表明,蝇蛹佣小蜂的产卵期为(8.93±3.34)d,单头雌蜂能产雌性后代(34.11±16.34)头和雄性后代(11.04±8.87)头,且雄性百分比为0.24±0.11.随成蜂日龄的增大,寄生蜂产生雄性后代的比率显著增加.蝇蛹佣小蜂在寄生家蝇蛹时,会优先选择寄生个体较大的蛹;在单次寄生的情况下,蝇蛹佣小蜂倾向于在较大的家蝇蛹内产出更多的雌性后代.     

Influence of previous herbivory on behavior and development of Spodoptera exigua larvae on glanded and glandless cotton

The solitary endoparasitoid Aenasius vexans Kerrich (Hymenoptera: Encyrtidae) is used for augmentative releases against the cassava mealybug, Phenacoccus herreni Cox & Williams (Sternorrhyncha: Pseudococcidae), an important pest on cassava in South America. In light of the need for large numbers of high quality females, experiments were conducted on host stage suitability and sex allocation. In choice and no-choice experiments, individual female wasps were offered second and third instar, as well as adult, hosts. During the first five days after emergence, the wasps showed a steady increase in the number of hosts they successfully parasitised per day, but the respective secondary sex ratio for each instar remained constant. Parasitism was highest for third instar hosts in no-choice tests, while in choice tests parasitism was highest in both third instars and adults. The later the developmental stage of the host at oviposition, the faster the parasitoids developed and emerged, and for each host stage, the development time of males was shorter than for females. The sex ratio of the wasps emerging from hosts that were parasitised as second instars was strongly male-biased, while the apparently preferred later stages yielded significantly more females than males. Female and male A. vexans emerging from hosts parasitised at the third instar were significantly larger than for the other stages. This may explain the preference for the third instar as well as the female-biased sex ratio, as size is usually positively correlated with higher fitness, especially in females. The results suggest that third instar hosts are the most suitable for rearing high numbers of large females.     

Effects of pre-adult and adult experience on host acceptance in choice and non-choice tests in two strains ofTrichogramma

The effect of adult learning through an oviposition experience, and pre-adult learning through development inside a host was investigated in two strains of an Australian egg parasitoid,Trichogramma nrivelae (Hymenoptera: Trichogrammatidae). Host response was measured in two types of laboratory preference tests. In single host tests, females reared on three lepidopteran hosts (Heliothis punctigera (Noctuidae),Papilio aegeus (Papilionidae), andHypolimnas bolina (Nymphalinae)) were presented host eggs individually, and allowed two ovipositions. Pre-adult experience affected host preference in only one strain, while acceptance of a host was increased in both strains when they had previously oviposited in this host species. An oviposition experience had a stronger effect on host preference than pre-adult experience. In choice tests, pairwise combinations of hosts were arranged in an alternating grid. The ratio of host acceptances to host contacts was computed for the whole test and up to the first oviposition. These indicated that effects of rearing host were weak or absent, but the host chosen initially had a strong effect on host preference. Relative size of the hosts had a strong effect on choice of the first host. The implications of learning inTrichogramma are discussed in relation to host preference testing procedures and the selection of candidate strains for mass rearing and inundative release.     

班氏跳小蜂对新寄主资源的寄生适合度

【目的】班氏跳小蜂Aenasius bambawalei是扶桑绵粉蚧Phenacoccus solenopsis的伴迁性天敌,迄今已知该寄生蜂只能寄生扶桑绵粉蚧,但是我们发现该寄生蜂还能成功寄生另一种外来有害生物——石蒜绵粉蚧P. solani。本研究旨在明确班氏跳小蜂对该新寄主资源的寄生适合度,为今后充分开发、利用该寄生蜂提供科学依据。【方法】在实验室条件下,以马铃薯Solanum tuberosum块茎作为粉蚧的寄主植物,测定了班氏跳小蜂对不同龄期石蒜绵粉蚧的寄生适合度,并在非选择条件下测定了上述两种寄主上僵蚧形成时间以及该寄生蜂羽化时间、寿命、后足胫节长度、寄生率、羽化率及子代性比。【结果】班氏跳小蜂可寄生石蒜绵粉蚧的雌成虫及2龄和3龄若虫,但只有寄生雌成虫才能正常羽化出蜂。分别以石蒜绵粉蚧与扶桑绵粉蚧为寄主时,最适合的蜂蚧比分别为2∶15和2∶20。不同寄主对僵蚧形成时间及班氏跳小蜂的羽化时间无显著影响,但显著影响班氏跳小蜂的寿命以及雌蜂后足胫节长度,尤其是扶桑绵粉蚧上羽化的寄生蜂的寿命比以石蒜绵粉蚧上的长约20 d。而且,班氏跳小蜂对扶桑绵粉蚧的寄生率(54.0%)显著高于对石蒜绵粉蚧的(25.3%),但班氏跳小蜂在这两种寄主上的羽化率均在90%以上,差异不显著;寄生扶桑绵粉蚧的雌蜂比例高于寄生石蒜绵粉蚧的雌蜂比例。【结论】班氏跳小蜂能寄生石蒜绵粉蚧,且只在雌成虫上完成世代发育;与在更适寄主扶桑绵粉蚧上比较,石蒜绵粉蚧上羽化的班氏跳小蜂在寿命及雌蜂个体大小上有劣势。     

RETRACTED ARTICLE: Foraging of Host-Habitat and Superparasitism in <Emphasis Type="Italic">Cotesia glomerata</Emphasis>: A Gregarious Parasitoid of <Emphasis Type="Italic">Pieris brassicae</Emphasis>

The study investigates differences in the oviposition pattern of a braconid parasitoid, Cotesia glomerata (Linn.) in Pieris brassicae (Linn.) in relation to their use of different cruciferous food plants. The response of P. brassicae to superparasitism and consequences for the parasitoid were examined in order to elucidate the ecological significance of this behaviour. Female parasitoid located various crucifers and searched for host more frequently almost on all the host plants tested i.e. cabbage, cauliflower, Chinese cabbage, broccoli and radish. According to the estimated relative number of female locating hosts, cabbage was the most attractive plant for C. glomerata and total number of eggs laid in host larvae feeding on it was higher than in larvae feeding on other plants. Laboratory experiments demonstrated that superparasitism reduced survivorship of P. brassicae larvae. Superparasitism lengthened parasitoid development and prolonged the feeding period of host larvae. Sex ratio and the body weight of emergent wasps correlated negatively with brood size. Despite a trade-off between maximising brood size and optimising the fitness of individual offspring, two or three ovipositions on P. brassicae larvae resulted in a greater female dry mass than did a single oviposition on the host. Thus, superparasitism might be of adaptive significance under certain circumstances, especially when host density is low and unparasitized hosts are rare in a habitat.     

Patch Time Allocation by the Parasitoid Diadegma semiclausum (Hymenoptera: Ichneumonidae). I. Effect of Interpatch Distance

We observed the foraging behavior of Diadegma semiclausum (Hymenoptera:Ichneumonidae), a larval parasitoid of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), in a wind tunnel to determine how interpatch distance affects patch time allocation. Individual female wasps were released onto an experimental patch infested with host larvae and were allowed freely to leave for an identically extrapatch placed upwind of the experimental patch with varying interpatch distances. The effects of interpatch distance and within-patch foraging experience on the patch-leaving tendency of the parasitoid were analyzed bymeans of the proportional hazards model. Increasing interpatch distance andunsuccessful host encounter as a result of host defense decreased the patch-leaving tendency, while successful oviposition and unsuccessful search time since last oviposition increased the patch-leaving tendency. Asa result, both patch residence time and number of ovipositions by D. semiclausum increased with increasing interpatch distance, which appears to agree with the general predictions of the marginal value theorem that a parasitoid should stay longer and parasitize more hosts with increasing interpatch distance.     

The Influence of Host Species on Some Biological and Behavioural Aspects of Dibrachys boarmiae (Hymenoptera: Pteromalidae), Parasitoid of Kermania pistaciella (Lepidoptera: Tineidae)

Dibrachys boarmiae was recently found as a parasitoid of the pistachio twig borer moth, Kermania pistaciella, an important pistachio pest in Iran. Several biological and behavioural aspects of the wasp were studied under controlled conditions using three different lepidopterous host species, K. pistaciella, Sitotroga cerealella and Galleria mellonella. Development time from egg to adult decreases from 54 days at 15°C to 12.6 days at 32.5°C. The thermal constant was estimated 270°D, and the lower development threshold was at 9.9°C. Longevity of females that had the opportunity to oviposit and access to food (honey) was on average 23 days, and 134 offspring were produced during 13 days of oviposition. Ninety percent of ovipositions occur during the first 10 days of the parasitoid's life, although no pre-oviposition period was found. If females were deprived of food, longevity as well as fecundity, were drastically reduced to 8 days and only 79 offspring respectively. Females were able to mate immediately after emergence and the sex ratio of the progeny was strongly female biased on all examined hosts, especially on the largest host G. mellonella (0.08 male). When females were kept with a male throughout their life, the total number of progeny decreased to 92 wasps on average but the sex ratio was unaffected. The parasitoid significantly preferred to attack the pre-pupal stage, and this influenced the size of clutches allocated to different host stages. The parasitoid laid larger clutches on bigger hosts.     

Suitability of five mealybug species (Hemiptera,Pseudococcidae) as hosts for the solitary parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

Anagyrus sp. nr. pseudococci is an endoparasitoid which has been used as a biological control agent of mealybug pests. In this study, we compared the suitability of five mealybugs species with different phylogenetic relationships and geographical origins as hosts of this parasitoid. The selected mealybugs were: (1) a Mediterranean-native species, Planococcus ficus, sharing a long co-evolutionary history with the parasitoid; (2) three exotic species, the Afrotropical Planococcus citri, the Australasian Pseudococcus calceolariae and the Neotropical Pseudococcus viburni, with a recent history; and (3) the Neotropical Phenacoccus peruvianus, with no previous common history with the parasitoid. Host suitability was assessed based on different fitness parameters, such as body size, developmental time, emergence rate and sex ratio. The parasitoid was able to complete development in all mealybug species. Nevertheless, its emergence rate significantly varied among mealybug species, with the highest values observed in Pl. ficus and Pl. citri, intermediate values in Ps. calceolariae and the lowest ones in Ps. viburni and Ph. peruvianus. The body size of adult wasp females varied with host suitability and was positively correlated with other measures of parasitoid fitness, including the emergence rate and the sex ratio. The parasitoid developmental time differed among mealybug species but did not correlate with any other measure of fitness. A female biased sex ratio was found in the parasitoid progeny emerged from all mealybug species, except in Ps. viburni and Ph. peruvianus. There was a direct relationship between the proportion of females in the parasitoid progeny and the emergence rate.     

Within-patch foraging behaviour of the aphid parasitoidAphidius funebris: plant architecture, host behaviour, and individual variation

The influence of plant architecture, host colony size, and host colony structure on the foraging behaviour of the aphid parasitoidAphidius funebris Mackauer (Hymenoptera: Aphidiidae) was investigated using a factorial experimental design. The factorial design involved releasing individual parasitoid females in aphid colonies consisting of either 10 or 20 individuals ofUroleucon jaceae L. (Homoptera: Aphididae) of either only larval instar L3 or a mixture of host instars, both on unmanipulated plants and on plants that had all leaves adjacent to the colony removed. Interactions between the parasitoid and its host were recorded until the parasitoid had left the plant. The time females spent on the host plant and the number of eggs laid varied greatly among females. Host colony size significantly affected patch residence time and the number of contacts between parasitoids and aphids. Plant architecture influenced the time-budget of the parasitoids which used leaves adjacent to the aphid colony for attacking aphids. Female oviposition rate was higher on unmanipulated plants than on manipulated plants. No further significant treatment effects on patch residence time, the number of contacts, attacks or ovipositions were found. Oviposition success ofA. funebris was influenced by instar-specific host behaviour. Several rules-of-thumb proposed by foraging theory did not account for parasitoid patch-leaving behaviour.     

Host-size-dependent sex ratio in a parasitoid wasp

Charnov's host-size model explains parasitoid host-size-dependent sex ratio as an adaptive consequence when there is a differential effect of host size on the offspring fitness of parasitoid males versus females. This article tests the predictions and the assumptions of the host-size model. The parasitoid wasp Pimpla nipponica Uchida (Hymenoptera: Ichneumonidae) laid more female eggs in larger or fresher host pupae when choice among hosts of different sizes or ages was allowed. Then, whether an asymmetrical effect of host size and age on the fitness of females versus males existed in P. nipponica was examined. Larger or fresher host pupae yielded larger wasps. Larger females lived longer, whereas male size did not influence male longevity. Large males mated successfully with relatively large females but failed with small females, whereas small males could mate successfully either with small or with large females. Thus, small-male advantages were found, and this held true even under male–male competition. Ovariole and egg numbers at any one time did not differ among females of different sizes. Larger females attained higher oviposition success and spent less time and energy for oviposition in hosts. Larger females produced more eggs from a single host meal. Taken together, females gained more, and males lost more, by being large. Host size and age thus asymmetrically affected the fitness of offspring males versus females through the relationships between host size or hast age and wasp size, which means the basic assumption of the host-size model was satisfied. Therefore, sex ratio control by P. nipponica in response to host size and age is adaptive. Received: November 13, 1998 / Accepted: January 18, 1999     

Fecundity and development of the ectoparasitic waspNasonia vitripennis are dependent on host quality

The gregarious, ectoparasitoidNasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) was offered pupae representing seven fly species, but only members of two families (Sarcophagidae and Muscidae) were parasitized. Host acceptance as an oviposition site did not imply host suitability for parasitoid growth:N. vitripennis produced fewer progeny, a higher proportion of males, required a longer development time, and produced smaller adult wasps onMusca domestica L. (Diptera: Muscidae) than on the three sarcophagid species tested [Sarcophaga bullata Parker,S. crassipalpis Macquart, andPeckia abnormis (Enderlein) (Diptera: Sarcophagidae)]. The physiological and nutritional status of a preferred host,S. bullata, influenced oviposition behavior and development ofN. vitripennis. Progeny allocation and sex ratio, which were regulated by the female parasitoid during oviposition, differed on living and dead nondiapausing hosts and on diapausing pupae. Differences in the host's nutritional condition was reflected in changes of the wasp's development time and adult body size. Envenomation was essential for successful development of the parasitoid on nondiapausing hosts, but venom injection byN. vitripennis did not increase the suitability of diapausing or dead pupae. The results suggest that wasp development is enhanced by changes induced in the host by parasitism.     

Development of a new attract‐and‐kill technology for Oriental fruit moth control using insecticide‐impregnated fabric

Various physiological effects of Wolbachia infection have been reported in invertebrates, but the impact of this infection on behavior and the consequences of these behavioral modifications on fitness have rarely been studied. Here, we investigate the effect of Wolbachia infection on the estimation of host nutritive resource quality in a parasitoid wasp. We compare decision‐making in uninfected and Wolbachia‐infected strains of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) on patches containing either fresh or old host eggs. For both strains, fresh eggs were better hosts than older eggs, but the difference was smaller for the infected strain than for the uninfected strain. Oviposition behavior of uninfected wasps followed the predictions of optimal foraging theory. They behaved differently toward high‐ vs. low‐quality hosts, with more hosts visited and more ovipositions, fewer high‐quality hosts used for feeding or superparasitism, and a sex ratio that was more biased toward females in patches containing high‐quality hosts than in patches containing low‐quality ones. Uninfected wasps also displayed shorter acceptance and rejection times in high‐quality hosts than in hosts of lower quality. In contrast, infected wasps were less efficient in evaluating the nutritive quality of the host (fresh vs. old eggs) and had a reduced ability to discriminate between unparasitized and parasitized hosts. Furthermore, they needed more energy and therefore engaged in host feeding more often. This study highlights possible decision‐making manipulation by Wolbachia, and we discuss its consequences for Wolbachia fitness.     

Host Preference and Progeny Sex Ratio in a Solitary Koinobiont Mealybug Endoparasitoid, Anagyrus Pseudococci (Girault), in Response to its Host Stage

Anagyrus pseudococci (Girault) , a koinobiont endoparasitoid , is a potential biological control agent of the citrus mealybug Planococcus citri (Risso) . This paper examines the effect of host stage of the mealybugs on the parasitoid preference , development , survival and sex ratio of the offspring . Host susceptibility and preference tests showed that the parasitoid had a significant preference for the older host instars . Percentage parasitization increased 4.8 - fold in the adult stage , compared with the second - instar host , although the parasitoid developed and emerged successfully from all stages . Mean developmental time for male parasitoids was faster than for the females . There was some evidence of delayed development of males in young hosts . Higher percentage emergence of parasitoid was observed from older mealybugs . A. pseudococci exhibited maternal adjustment of sex ratio as a function of host size with an increased proportion of females with the increasing host size . Females maximized their fitness by adjusting offspring sex ratio in response to host size without evaluating the future host quality . This information is important for mass rearing of A. pseudococci and for evaluating it in a biological control programme for P. citri.     

The developmental strategies and related profitability of an idiobiont ectoparasitoid Sclerodermus pupariae vary with host size

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