Protein expression during parasite redirection of host (Trichoplusia ni) biochemistry

Expression of proteins during normal egg and larval development of Trichoplusia ni was compared with that occurring in hosts stung as eggs by the parasitic wasp Chelonus sp. near curvimaculatus. Those stung hosts which produced a parasite (truly parasitized), precociously expressed proteins associated with larval-pupal metamorphosis, as did those stung hosts which did not contain a developing endoparasite (pseudoparasitized). No highly abundant, low-intermediate molecular weight hemolymph proteins were observed in truly or pseudoparasitized larvae which did not also occur at some point in the development of normal larvae. A low abundance, high molecular mass (160,000 Da) protein was observed in the hemolymph of truly parasitized larvae, but not of normal or pseudoparasitized larvae. The protein is glycosylated and very acidic (pI near 4.5). The data show that any parasitization proteins injected or induced by the ovipositing female parasite are in low abundance, in contrast to situations reported for parasitic wasps which sting hosts as larvae.     

Chelonus sp.: suppression of host ecdysteroids and developmentally stationary pseudoparasitized prepupae

When eggs of the caterpillar Trichoplusia ni are stung by Chelonus sp. (near C. curvimaculatus) (Braconidae), the developing host larvae precociously spin a cocoon but then remain developmentally stationary in the prepupal stage. The latter event happens even in hosts which were stung and precociously spin cocoons but which, upon dissection, contain no obvious parasite. Injection of radiolabeled ecdysone into either pseudoparasitized or allatectomized larvae demonstrates suppressed rates of conversion of ecdysone to 20-hydroxyecdysone when compared with controls. The data indicate that the occurrence of developmentally stationary pseudoparasitized prepupae is due to less production of ecdysteroid and less conversion of ecdysone to 20-hydroxyecdysone, both probably as a result of suppressed juvenile hormone titer.     

Parasite regulation of host insect metamorphosis: a new form of regulation in pseudoparasitized larvae ofTrichoplusia ni

Summary When eggs ofTrichoplusia ni (Lepidoptera) are stung by a parasitic wasp,Chelonus sp., the developing host larvae precociously initiate metamorphosis ten days later. Precocious initiation of metamorphosis occurs even in ‘pseudoparasitized’ stung hosts which contain no living parasites at the time of symptoms of host regulation by the parasite. In feeding, penultimate instar, pseudoparasitized hosts, the corpora allata activity, hemolymph juvenile hormone esterase activity, in vivo rates of juvenile hormone metabolism and changes in hemolymph protein composition all follow the pattern of the normal last instar. This and other evidence suggests the entire developmental pattern of the last larval instar is precociously expressed in penultimate instar, pseudoparasitized hosts. The cause of precocious expression of the developmental program leading to metamorphosis is a significant decrease in the critical size parameter that, in normal larvae, signals attainment of the last instar. The induction, in preultimate instar larvae, of the entire feeding stage developmental program leading to metamorphic commitment, using either biochemical, surgical or parasitic experimental probes, has not been previously reported. The results have important implications for the study of host-parasite endocrine interaction, of normal insect metamorphosis and even of human puberty.     

Possible bases of pseudoparasitism in Spodoptera littoralis larvae stung by Microplitis rufiventris

The effects of host age and parasitoid female age on the occurrence of 'Pseudoparasitism', using the Spodoptera littoralis-Microplitis rufiventris host-parasitoid system were investigated. The first four larval instars of the host are not equally suitable for parasitoid development. The proportion of pseudoparasitized hosts significantly increases when: (1) the age of the female parasitoid increases; (2) oviposition occurs mostly in fourth instar larvae; (3) a later age of the host instar is used; (4) the mandibles of the newly hatched parasitoid larvae mistakenly attack host interior organs (e.g. Malpighian tubules); and (5) an imperfect growth pattern of teratocytes occurs. The reluctance of female wasps to parasitize fourth instar host larvae is not due to the thickness of host cuticle but possibly due to the unfavourable physiological state of the host larvae. The age of host larvae at the time of parasitization may influence the adverse effects of parasitoid factors (e.g. polydnavirus, venom and teratocytes) on the growth of host larvae. It is suggested that females of M. rufiventris are able to determine the suitability of a potential host instar for the development of their offspring. The cell diameter of M. rufiventris teratocytes increases with increasing age of host larvae at the time of oviposition. The association within the host of living parasitoid larvae and functional teratocytes may be important for the survival of each other and consequently for successful parasitism.     

Is the host or the parasitoid in control?: effects of host age and temperature on pseudoparasitization by Microplitis rufiventris in Spodoptera littoralis

We compared the production of pseudoparasitization by Microplitis rufiventris females in most (third) and less (fourth) preferred instars of Spodoptera littoralis larvae at 20+/-1 and 27+/-1 degrees C. The parasitized hosts were classified into hosts producing parasitoids (type A hosts) and hosts producing no parasitoids, i.e., pseudoparasitized hosts (type B hosts). The latter were further classified into: (a) pseudoparasitized hosts with "well" arrested development (type B1 hosts); (b) pseudoparasitized hosts with partially arrested development (type B2 hosts); and (c) pseudoparasitized hosts that successfully pupated to apparently normal host pupae (type B3 hosts). The present series of experiments showed that parasitization by M. rufiventris was clearly affected by host instar, age within an instar and rearing temperature. Production of type B hosts was less when third instar S. littoralis larvae were exposed to the wasp females than when the host larvae were in fourth instar. The production of type A hosts was much greater when early or mid ages of an instar was stung by the wasp females comparing with stung late age of the same instar. Production of type B hosts may be due to one or overall of the following: (a) dosage dilution of M. rufiventris female's factors in the different age classes of the instar; (b) endocrine system (physiological state) at parasitization time, i.e., early vs late age of the instar; (c) growth rate of host larvae. The lowest production of type B hosts was at highest growth rate; and (d) temperature, larger proportions of type B hosts were produced at 27+/-1 than at 20+/-1degrees C. The three types host development (B1, B2 and B3) are possibly representing three levels of host resistance (host control) resulting in partial or complete failure of parasitoid control. Type A hosts represent complete success of parasitoid control. The results suggest that the impact of parasitoid factor(s) on developmental arrest is affected by host age at the time of parasitism and/or by temperature.     

A biological review of the genusEuplectrus [Hym.: Eulophidae] with special emphasis onE. Laphygmae as a parasite ofSpodoptera littoralis [Lep.: Noctuidae]

The life history and behavior ofEuplectrus laphygmae Ferrière were studied. The parasites paralyse the host larvae temporarily before ovipositing 1–2 eggs on their dorsum. Egg and larval development takes place externally in the location of egg deposition and pupation is in a silken cocoon under the dead host. Development lasts 11.7 days for both sexes. The eggs are attached to the host with a pedicel that is inserted under the cuticle but above the hypodermis, and which may have physiological and mechanical functions. The adult parasites host-feed, but do not lay on the same host. All hosts stung by parasites die, regardless whether oviposition has occurred, or whether host larvae develop upon them. Multiparasitism with internal parasites ofSpodoptera littoralis (Boisd.) was observed. A comparison with otherEuplectrus species was made. They have a wide range of lepidopterous hosts but very similar biological characteristics. Only very few utilizations for biological control have been reported with this genus.     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

Regulation of wing formation and adult development in an aphid host, Aphis fabae, by the parasitoid Aphidius colemani

Nymphs of presumptive winged gynoparae of Aphis fabae (Hemiptera: Aphididae), were exposed to female parasitoids, Aphidius colemani (Hymenoptera: Aphidiidae) and stung once with the ovipositor. Wing development was inhibited and, when aphids were parasitised during the early stages, they did not reach the adult stage but mummies with rudimentary or no wingbuds are observed in the host's fourth-stadium. These and previous studies have suggested that wing development may be inhibited by factor(s) from the maternal parasitoid injected into the host at the time of oviposition. In an attempt to identify such factor(s), saline extracts of whole female parasitoids, abdomens, ovaries and venom glands were prepared. When a saline extract of venom glands was injected into late-second-stadium aphids, many develop to fourth-stadium nymphs with rudimentary wingbuds, indicating an effect on wing formation but also showed developmental arrest and often died when attempting to moult to the adult stage. It appears that host death may be related to physiological/biochemical interactions of parasitoid and host rather than just late stage parasitoid larvae ingesting the host's vital organs. Injections with extracts into later host stadia gave similar results with regard to development to the adult, although aphids injected in the late-fourth-stadium develop normally to the adult stage with no effect on wing formation. The results indicate that the earlier the injection before the final moult the greater the effect of the injected extract on preventing adult development.Extracts prepared from head + thorax do not affect aphid development and the results indicate that there is an active factor(s) - likely a protein - in the female parasitoid's venom that disrupts wing development and/or inhibits development to the adult stage. Surprisingly, injections of extracts from male parasitoids have similar effects but the location and function of such a factor(s) in males are unknown.     

Butterfly oviposition preference is not related to larval performance on a polyploid herb

The preference–performance hypothesis predicts that female insects maximize their fitness by utilizing host plants which are associated with high larval performance. Still, studies with several insect species have failed to find a positive correlation between oviposition preference and larval performance. In the present study, we experimentally investigated the relationship between oviposition preferences and larval performance in the butterfly Anthocharis cardamines. Preferences were assessed using both cage experiments and field data on the proportion of host plant individuals utilized in natural populations. Larval performance was experimentally investigated using larvae descending from 419 oviposition events by 21 females on plants from 51 populations of two ploidy types of the perennial herb Cardamine pratensis. Neither ploidy type nor population identity influenced egg survival or larval development, but increased plant inflorescence size resulted in a larger final larval size. There was no correlation between female oviposition preference and egg survival or larval development under controlled conditions. Moreover, variation in larval performance among populations under controlled conditions was not correlated with the proportion of host plants utilized in the field. Lastly, first instar larvae added to plants rejected for oviposition by butterfly females during the preference experiment performed equally well as larvae growing on plants chosen for oviposition. The lack of a correlation between larval performance and oviposition preference for A. cardamines under both experimental and natural settings suggests that female host choice does not maximize the fitness of the individual offspring.     

Testing adaptive significance of host manipulation with a parasitoid wasp

According to the extended phenotype hypothesis, certain parasites manipulate the host's behaviour which ultimately enhances the transmission of parasite genes into the next generation. The parasitoid wasp Ampulex compressa attacks and stings its cockroach Periplaneta americana host and lays an egg on the cockroach's leg. Before the wasp's oviposition, the stung cockroach engages in excessive self-grooming for about 30 min. The prey location hypothesis posits that self-grooming may allow the wasp to easily locate its host before transporting it to the nest. To test this hypothesis, we manipulated the mobility of the stung cockroach under different spatial constraints. Latencies to locate stung cockroaches with unlimited movement were similar than latencies to locate stung, but motionless cockroaches irrespectively of spatial constraints. Wasps were less willing to lay eggs and seal an entrance to the burrow in treatments with motionless cockroaches which suggests that if the expected reproductive success is low, then parental investment decreases. Our results provide no support for the location hypothesis and call for further experimental investigation of the extended phenotype hypothesis in parasite–host interactions.     

Factors affecting the ability of the wasp parasite Pseudeucoila bochei to inhibit tumourigenesis in Drosophila melanogaster.

The cellular immune reaction of Drosophila melanogaster larvae which results in encapsulation of internal metazoan parasites is similar to the autoimmune reaction made by certain tumourmutant stocks against abnormally developing host tissues. The wasp parasite Pseudeucoila bochei is capable of actively inhibiting the haemocytic encapsulation reaction of host larvae, and this activity can also inhibit the haemocytic response made by the bw tu mutant flies against abnormal fat body tissue. The ability of the parasite to suppress tumourigenesis is dependent on the age of the host at the time of infection, and on the amount of previous oviposition of the parasite. The earlier during host development parasitisation occurs the more tumour formation is inhibited. partially spent females are less able to inhibit tumours than are newly emerged parasites and unspent parasites of the same age. In some parasitised individuals the tumour response is incomplete and consists of small pigment particles instead of the large melanotic growths characteristic of the strain. The autoimmune response made against “alien” host tissues is specific and does not interfere with the successful development of the parasite.     

Host-handling behavior of the parasitoid,Diglyphus minoeus [Hym.: Eulophidae], parasitizing the honeysuckle leaf-miner,Phytomyza lonicerae [Dipt.: Agromyzidae]

The host-handling behavior of individual female waspsDiglyphys minoeus which attack the larvae of the honeysuckle leaf-miner,Phytomyza lonicerae, include 4 types of behavior: probing, ovipositor insertion, host-feeding, and resting. Ovipositor insertion may either be injection of venom, probing of the host by the sensilla on the ovipositor's tip or egg laying. Three types of attacks were distinguished: oviposition attack for unparasitized larvae, host-feeding attack for unparasitized host larvae and host rejection for previously parasitized host larvae. Oviposition attack was characterized by frequent alternation between probing and ovipositor insertion, long duration of ovipositor insertion and resting, and the long duration of host-handling. Resting behavior is thought to protect the progeny against superparasitism, host-feeding by other wasps or hosts' recovery from paralysis. Host-feeding attack was characterized by frequent alternation between host-feeding and ovipositor insertion and long duration of host-feeding. Host rejection was composed mainly of probing and ovipositor insertion and short handling time.      

Effects of male-female rations on mating and egg production in Octomyomermis muspratti (Mermithidae: Nematoda)

Octomyomermis muspratti, a mermithid parasite of mosquito larvae, molted to the adult stage in 4–16 days. When male-female ratios were relatively high (1:2), mating and oviposition began soon after maturation, and oviposition was completed in 21–40 days. The number of females developing eggs increased with a corresponding increase in the male-female ratio. About 60% of the females completed oviposition at male-female ratios of 1:20, and about 100% completed oviposition as the male-female ratios were increased to 1:2. No egg development was observed in the absence of males. Male O. muspratti were capable of mating with a number of females and remained reproductively active for at least 50 days after a maturation at 26–28°C.     

Experience acquisition by Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae)

We investigated experience acquisition (alpha-conditioning) by females of the parasitoid Trichogramma australicum using host eggs of the noctuid moth Helicoverpa armigera (Hübner). We compared the acceptance of a host egg by females with different levels of ovipositional experience. The level of experience was designated using the standard oviposition sequence: (1) host contact (C); (2) host examination (E); (3) drilling (D); (4) full insertion (FI); and (5) oviposition (O). Each treatment consisted of a single experience level, but together these consituted a qualitative behavioural continuum of oviposition experience from naive (N) to experienced wasps. We found that host experience by adult T. australicum females can modify their behaviour. Mean duration of host finding was: N = C > E = D > FI = O. Mean duration of host examination and full insertion were: N = C > E = D = FI = O. Drilling was constant for all experience levels. Experience in drilling of the chorion during the previous host-exposure process represents a critical experience for a female and results in efficient handling and more ready acceptance of a subsequently encountered host egg.     

桔小实蝇和番石榴实蝇对6种寄主果实的产卵选择适应性

植食性昆虫对寄主植物的选择适应性是研究昆虫和植物协同进化关系的核心内容之一。评估寄主植物对植食性昆虫种群的适合度,需要综合分析昆虫对寄主的产卵选择性和寄主对昆虫的取食适合性。以桔小实蝇和番石榴实蝇为研究对象,分别测定了这两种实蝇对6种寄主果实:番石榴、香蕉、杨桃、木瓜、甜橙、番茄的产卵选择性以及幼虫取食后对其生长发育的影响。寄主产卵选择性实验分别采用完整寄主果实直接供试产卵和块状寄主果实气味引诱产卵两种处理方式;在生长发育适应性实验中,以幼虫和蛹的存活和生长发育等相关参数作为评价指标。实验结果表明,寄主的供试方式不同,两种实蝇的选择性均有明显差异;对寄主气味选择性强的寄主更适合于两种实蝇后代的生长发育。两种实蝇对6种寄主果实的产卵选择性和后代发育适合性两者相关性不显著,与许多文献报道单一地采用发育适合性(如发育历期、存活率或蛹重等)作为评价寄主选择性的结果不一致。两种实蝇之间对6种寄主果实的产卵选择和幼虫取食适合性既具相似性也具差异性,表明这两种实蝇在寄主生态位上既有重叠性又有分化性。     

Effect of entomopoxvirus infection of Pseudaletia separata larvae on the oviposition behavior of Cotesia kariyai

Parasitoid behavior and oviposition were monitored to investigate the ability of Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae) to distinguish between entomopoxvirus-infected and noninfected larvae of Pseudaletia separata Walker (Lepidoptera: Noctuidae). Comparison of individual means revealed that searching time was not significantly different between treatments. Ovipositional time, however, differed significantly after day 8 post virus inoculation. The parasitoid adopted ovipositional posture on infected and noninfected host irrespective of the stage of infection and did not distinguish infected from noninfected larvae up to 4 days post infection. Mean number of larvae stung by the parasitoid was not influenced by the length of time interval between exposure to the virus. However, duration of ovipositor insertion was influenced by the time interval between exposure to the virus and subsequent exposure to parasitoid females. Female parasitoids did not completely reject infected larvae as unsuitable for egg deposition. However, 5 days after virus inoculation they rejected significantly more infected than noninfected larvae. Furthermore, significantly more eggs were laid in noninfected than infected larvae from day 5 following virus administration. These observations suggest that probing by Cotesia kariyai may provide information concerning host suitability.     

A radiographic method for rapid detection ofHylemya brassicae puparial parasitism

The efficiency of detecting parasitism in puparia ofHylemya brassicae (Bouché) with X-radiography was established as 92% as compared with results of actual rearing. The technique is more efficient with host puparia collected in the spring than in the previous fall, because both host and parasite are in more advanced developmental stages. the procedure did not affect host adult emergence, host oviposition, host egg hatching, or parasite emergence.     

Effects of Asobara japonica venom on larval survival of host and nonhost Drosophila species

Abstract Ovipositing Asobara japonica females inject venom (containing paralysis‐inducing factors) immediately after the insertion of their ovipositors into Drosophila larvae, and lay eggs a little later. Interruption of their oviposition behaviour before egg laying causes high larval mortality in host Drosophila species, whereas normal oviposition does not. This suggests that venom of this parasitoid is toxic to larvae of these host species but its toxicity is suppressed by factor(s) provided by parasitoid females at the time of laying egg or by parasitoid embryos developing in the hosts. On the other hand, venom does not show toxicity to larvae of nonhost Drosophia species. Possible functions of venom are discussed.     

中华花翅跳小蜂生物学特性和种群动态的研究

中华花翅跳小蜂Microterys sinicus Jiang是白蜡虫成虫产卵期的主要天敌。该蜂成虫喜在自然光下活动,取食和交配都在寄主树上进行。中华花翅跳小蜂每雌平均怀卵量34.39粒,产卵前期2～3天。产卵量、产卵率和产卵天数与温度密切相关,27℃时产卵量和产卵率最高。30℃时产卵天数最少。21～27℃卵孵化率达80%以上。幼虫共5龄。每头跳小蜂幼虫平均取食蜡虫卵数分别为：1龄14.6粒,2龄29.8粒,3龄69.4粒,4龄126.9粒。5龄幼虫不取食。全代发育起点温度和有效积温分别为11.84℃和574.32日·度。补充营养能显著延长成虫寿命和产卵天数,提高雌虫产卵量。中华花翅跳小蜂成虫在田间有两个高峰期,分别发生在4月上中旬和5月中下旬。每粒虫囊内跳小蜂幼虫数与白蜡虫健卵百分率呈负指数关系,拟合方程为：Y=96.0829Exp(-0.1872x)。