Effects of physiological condition and experience on oviposition behaviour of Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) on eggs of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

We produced an ethogram for and investigated effects of physiological condition and experience on oviposition behaviour for Trichogramma australicum on Helicoverpa armigera eggs. The data, coupled with the ethogram, have enabled the establishment of standard behavioural categories which can be used to assess acceptability of H. armigera eggs to T. australicum reared in vitro or in eggs of other species. Physiological and experiential conditions were investigated using females of three different ages (0–24, 24–48 and 48–72 h old), two types of sexual states (mated and unmated) and two types of ovipositional experience (naive and experienced). Durations of host finding, host examination, and post-ovipositional re-examination were reduced by oviposition experience and were shorter in younger females (0–48 h old). Oviposition experience reduces the duration of the drilling and percentage of females host-feeding. Being mated and young reduces the host examination time in subsequent oviposition bouts. Only ovipositionally inexperienced females host-feed before oviposition and host-fed more frequently than experienced individuals after oviposition. Host-feeding needs consideration for optimal culture.     

Influence of rearing hosts on host size acceptance by Trichogramma australicum

We investigated the acceptance of different sized host models by Trichogramma australicum in the laboratory. We used isoline cultures of T. australicum reared in hosts of different sizes. Helicoverpa armigera represent relatively large hosts, and those of Sitotroga cerealella are small, termed the Ha and Sc biotypes, respectively. Five sizes of glass beads were tested for acceptance: diameter 0.5, 0.75, 1.0, 1.5 and 2.0 mm. The acceptance of a host model was determined by persistent attempted drilling of a glass bead by a female. The relationship between host egg size and number of eggs laid by a female was also investigated. We used three sizes of artificial egg (diameter 0.75, 1.00, and 1.50 mm of hemispherical cupules) each containing artificial diet. Ha biotype wasps accepted host models in the range 0.75--1.50 mm dia. (vol. 0.166--1.325 l), whereas those of the Sc biotype accepted host models in the range 0.50--1.00 mm dia. (vol. 0.05--0.393 l). This evidence suggests a lineal (possibly genetic) influence to host size acceptance for T. australicum, dependent on the size of the host in which the wasp has been reared. Also T. australicum lay fewer eggs in smaller artificial eggs than in larger ones. The role of host size in host acceptance and number of eggs delivered, and its implications, is discussed.     

Oviposition Behaviour and Reproductive Performance of Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) Reared in Artificial Diet

Biotypes of Trichogramma australicum were reared on artificial diet "A", Helicoverpa armigera (Hübner) (natural host) eggs and Sitotroga cerealella (Olivier) (factitious host) eggs. We evaluated the quality of these biotypes by comparing their oviposition behaviour and reproductive performance on H. armigera eggs. Female T. australicum reared in vitro accepted H. armigera eggs for oviposition and displayed similar behavioural components of oviposition to females reared on natural hosts. However, handling time during oviposition in H. armigera eggs by females from in vitro rearing was significantly longer than handling time of females reared on the natural host because the females needed a significantly longer time for host feeding. In vitro reared females produced significantly more progeny and parasitised more H. armigera eggs than the females reared on S. cerealella. Improvements to the artificial diet for T. australicum may reduce handling time of the in vitro reared females and increase the female population. These improvements may include changes in nutrient content and size of the artificial eggs.     

Does the Polyphagous Egg Parasitoid <Emphasis Type="Italic">Trichogramma platneri</Emphasis> Nagarkatti (Hymenoptera: Trichogrammatidae) Display Behavioral Plasticity When Parasitizing Different Hosts?

Trichogramma platneri oviposition behavior on Amorbia cuneana egg masses was investigated under laboratory conditions. No relationship was detected between host surface area, number of edge turning on host eggs, and parasitoid clutch size. It was also observed that females parasitized the egg mass randomly by drilling into the egg mass and parasitizing individual eggs without using stereotypical behaviors to assess individual hosts (i.e. drumming and turning). However, clutch size did change due to ovipositional experience as naïve wasps with little or no ovipositional experience (<6 eggs parasitized), allocated significantly more progeny per host than wasps with longer ovipositional experience (24-h oviposition experience on a single egg mass). Moreover, naïve wasps parasitized significantly more eggs on the outer edge of the egg mass than experienced wasps. We contend that the physical characteristics of A. cuneana eggs and egg masses preclude T. platneri from completely discriminating between individual eggs. However, because T. platneri may be using kairomones from the egg mass, this described oviposition strategy remains effective.     

亚洲玉米螟成虫寿命与繁殖力的地理差异

为探明亚洲玉米螟Ostrinia furnacalis繁殖力的地理差异,比较了亚洲玉米螟5个不同地理种群海南乐东(LD)、江西南昌(NC)、山东泰安(TA)、河北廊坊(LF)和黑龙江哈尔滨(HEB)的成虫寿命、产卵历期、产卵量,并分析了这些参数与各种群地理纬度的关系.成虫寿命随纬度升高而延长,从南到北各种群雌虫寿命分别为10.20、13.68、13.90、13.95 d和16.40 d,雄虫寿命分别为8.35、12.50、13.62、13.71 d和14.30 d;产卵历期随纬度升高而延长,从南到北各种群分别为7.45、10.45、11.90、10.62d和13.15 d;产卵量随纬度升高而增大,乐东产卵量显著低于其他种群,从南到北各种群产卵量分别为351.55、500.09、522.90、546.76粒和577.95粒/雌.这些研究结果初步揭示了亚洲玉米螟繁殖略策的地理差异.     

Motivation models fail to explain oviposition behaviour in the diamondback moth

Abstract. It is widely accepted that previous experience and internal physiological factors (such as egg‐load) affect host‐plant discrimination during oviposition by phytophagous insects. However, there is some debate as to how these factors interact in a mechanistic sense to control acceptance. The role of learning and host deprivation in host acceptance by adult diamondback moths (Plutella xylostella L.) was investigated. In the first experiment, we tested whether experience of a lower ranked host cabbage increased acceptance of a higher ranked host as predicted by a hierarchy threshold model. Moths trained on cabbage were over three times more likely to accept cabbage during testing than untrained moths. There was no effect of cabbage training on acceptance of cress, indicating that the effect of training was species‐specific. In a second experiment, designed to test the prediction of motivation models that insects become less discriminating when deprived of oviposition opportunities, depriving females of host plants for 2 nights significantly increased female egg‐load (×2.3). Host deprivation did not decrease discrimination between the preferred host cress and cabbage. Cabbage and cress plants were equally likely to have been accepted by nondeprived moths after 1 night of exposure, yet moths deprived of hosts for 2 nights strongly preferred cress when tested during the first 20 min of the scotophase. During this 20‐min period, previous host deprivation increased acceptance of host plants generally but did not decrease discrimination between hosts. These data contradict the expectation that there is an inverse relationship between host species discrimination and the failure of an insect to find hosts as found in existing oviposition acceptance models. As an alternative, the Incremental Acceptance Model of host acceptance behaviour is presented, in which responsiveness to a host is a function of the recent encounter rate with host‐specific stimuli, and the oviposition reflex is regulated by nonspecific cues such as egg‐load.     

Effects of egg load on finding and acceptance of host fruit in Ceratitis capitata flies

Abstract. In studies conducted on potted host trees in field cages and in the laboratory, we examined the influence of egg load on the finding and acceptance of high-ranking (kumquat) and lower-ranking (grapefruit) hosts for oviposition by wild-origin Mediterranean fruit fly females, Ceratitis capitata (Wiedemann). By prescribing the periods during which females had access to protein prior to testing, we generated four classes of females having progressively increasing egg loads but not differing in population origin, age, degree of protein hunger at testing, or amount of prior experience with host fruit (none). Egg load had no discernible effect on behaviour associated with finding either type of fruit but did have a significant effect on several behaviours associated with oviposition after alighting on fruit. Increasing egg load led to increasing propensity to engage in ovipositional-type behaviour on both kumquats and grapefruits. There was no evidence, however, to support a hypothesis that medflies would become less discriminating against grapefruits relative to kumquats as egg load increased. Relative to kumquats, grapefruits were accepted for oviposition by intermediate and high egg load females to a substantially greater degree in laboratory cages than on trees, suggesting that results of laboratory cage experiments on host discrimination by tephritid flies may poorly reflect differences in behavioural responses expressed under less constrained conditions.     

Host-plant acceptance and performance of Tetranychus urticae (Acari, Tetranychidae)

Abstract: Tetranychus urticae is a serious pest of several crops worldwide. It performs differentially on diverse host‐plant species. Because dispersion is mainly passive, the process of host‐plant selection should be viewed in terms of host‐plant acceptance and not in terms of host finding. The objectives of this study were to investigate: (1) the acceptance of strawberry (S) in comparison with onion (O), leek (L) and parsley (P) by T. urticae; and (2) the suitability of these host plants for the performance of T. urticae, in terms of fecundity and survival. Host‐plant acceptance was measured through females that settled on a test plant or females that left for another host plant. In another experiment, for a duration of 5 days, individual newly mated females were assigned to discs of each host plant and the fecundity, the maximum number of offspring obtained from one female that settled on the disc, the survival and the percentage of females that oviposited at least one egg were analysed. A choice test to measure the preference of females for different host plants was performed. Movements took place towards (S) from the three plants: (O), (L) and (P). Mites significantly moved to other places in the Petri dishes from leek‐origin discs. Dispersal of T. urticae from (S) to other host‐plant discs was similar for all plants. Mean fecundity was higher on (S) than on the other plants. The maximum number of offspring per female was highest on (S), lowest on (L) and (O), and intermediate on (P). Survival of females and percentage of females that laid at least one egg were independent of the host plant. The choice test showed that oviposition was higher on (S) and (P) and very poor on (L) and (O) and that more females settled on (S) and (P). Although mites migrated from parsley to strawberry, the first host plant has a higher acceptance of T. urticae in terms of maximum number of offspring per female than onion and leek, and a lower performance in terms of fecundity than strawberry. Parsley could be a good candidate for an associate plant in a strawberry crop; however, it needs more research under field conditions.     

Inheritance and plasticity of adult host acceptance in Yponomeuta species: implications for host shifts in specialist herbivores

Changes in host acceptance is an important factor in the host specialization of phytophagous insects, and knowledge of the genetic organization of this behaviour is necessary in order to understand how host shifts occur. Here we describe the inheritance of adult host acceptance (oviposition) in three closely related species of Yponomeuta Latreille (Lepidoptera: Yponomeutidae), and their interspecific hybrids. Yponomeuta cagnagellus (Hübner), a specialist on Euonymus europaeus L. (Celastraceae), Y. malinellus Zeller, a specialist on Malus spp. (Rosaceae), and Y. padellus (L.), oligophagous on a number of Rosaceae, were tested for their acceptance of parental hosts in choice tests. Acceptance of E. europaeus is semi‐dominant in hybrids of Y. cagnagellus×Y. padellus, and in hybrids of Y. cagnagellus×Y. malinellus. The dominance of this acceptance was confirmed in oviposition tests with backcross hybrids: backcross hybrids F1 × Y. cagnagellus oviposited mainly on E. europaeus and F1 × Y. padellus still deposited more than half of their egg masses on E. europaeus. Reciprocal hybrids did not differ in their host acceptance, indicating that the trait is autosomal. We further studied the effect of larval food on adult host acceptance (‘Hopkins host selection principle’) in split full‐sib F1 families. Larval diet influenced oviposition only in one of two hybrid crosses. The F1 hybrid of Y. padellus× Y. cagnagellus, reared on Prunus spinosa L., deposited a significantly lower percentage of egg masses on E. europaeus compared to their full‐sib sisters fed with E. europaeus. We did not find this in the reciprocal cross. However, still more than half of the egg masses are deposited on E. europaeus by hybrids that have no experience on this host. We conclude that the semi‐dominant character of acceptance of E. europaeus and a tendency of Rosaceae‐feeding Yponomeuta to deposit egg masses on this host may have created the opportunity for the host shift of the predecessor of Y. cagnagellus from Rosaceae to the Celastraceae. This shift may have been further facilitated by a weak tendency of adults to oviposit on their larval food source.     

Does fecundity drive the evolution of insect diet?

We investigate whether egg load (a surrogate for fecundity) drives host specificity in a herbivorous insect. In many insects, including our study organism (Edith's checkerspot butterfly), both egg load and tendency to accept low-ranked hosts increase during each search for an oviposition site. Effects on host acceptance of egg load and passage of time are thereby potentially confounded. We conducted two experiments designed to disentangle these effects. In both experiments, we estimated the times of first acceptance of both a high-ranked and a low-ranked host, without allowing the insects to oviposit. In the first experiment, we measured egg load at the time of first acceptance of the low-ranked host. The later the time of first acceptance, the higher was the fecundity. We therefore reject the hypothesis that all insects accepted the low-ranked host at the same predetermined egg load. In the second experiment, we measured egg load 48 h after the high-ranked host was first accepted. We found no relationship between egg load and timing of acceptance of the low-ranked host. Insects with higher rates of egg accumulation did not accept the low-ranked host sooner. Taken together, these results suggest that acceptance of the low-ranked host is not driven directly by egg load. Rather, this acceptance results from some other process that is influenced by time since last oviposition. We conclude that there is no evidence to support the assumption that females with high rates of egg accumulation are more likely to accept low-ranked hosts.     

Host discrimination modulates brood guarding behaviour and the adaptive superparasitism in the parasitoid wasp Trissolcus semistriatus (Hymenoptera: Scelionidae)

Because hosts utilized by parasitoids are vulnerable to further oviposition by conspecifics, host guarding benefits female wasps. The present study aims to test whether female adults regulate brood guarding behaviour by host discrimination in a solitary parasitoid Trissolcus semistriatus by presenting an intact or parasitized host egg mass to a female adult. Virgin females without oviposition experience have host discrimination ability, which enables them to adjust the number of eggs laid in the hosts. Mating experience increases superparasitism by female adults, whereas mated females achieve a higher discrimination ability as a result of oviposition experience and show a lower superparasitism rate. As expected, females exhibit brood guard after parasitizing an intact host egg mass, whereas those females visiting a previously parasitized host egg mass, do not. Because the survival of eggs in superparasitized hosts is relatively low, regulating brood guarding behaviour by host discrimination is adaptive for female wasps.     

Increased host acceptance in experienced females of the parasitoid Brachymeria intermedia: which types of oviposition behaviour contribute to experience?

Brachymeria intermedia (Nees) (Hymenoptera: Chalcididae) is a solitary endoparasitoid of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae). The probability that a wasp will parasitise this host is increased if she had a previous oviposition experience. We investigated which types of pre-oviposition and oviposition behaviour induced this change by comparing the acceptance behaviour of wasps with zero to five oviposition experiences as well as wasps with various partial host handling experiences (from no contact with a host to one complete oviposition sequence). The percentage of females accepting the host increased gradually with both the number of previous oviposition experiences and the amount of handling of a single host. Furthermore, the naive females were less likely (44%) to walk to the host than females with a variety of experiences (72–100%). A single antennal contact with the host was sufficient to increase the probability of walking to the host. Additional handling and additional oviposition experiences further elevated the propensity to oviposit. Thus, the modification of the acceptance behaviour through experience was essentially a gradual process in which antennal contact with a pupa was a major element. It is suggested that naive wasps learned the host odour when they first antennated a pupa. As a result, they were attracted to the host odour in subsequent encounters.     

Oviposition site selection in Cactoblastis cactorum (Lepidoptera): constraints and compromises

Summary Oviposition by Cactoblastis cactorum on Opuntia ficus-indica and O. aurantiaca was assessed from the positioning of egg sticks on plants in the field. The number of egg sticks laid on O. ficus-indica plants was affected by: (1) plant size; (2) moth emergence near the plant; (3) cladode condition; and (4) plant conspicuousness. These factors contributed towards the clumping of egg sticks on plants. There was no apparent oviposition preference for one of the two host plant species despite the fact that egg predation was higher and fecundity lower on O. aurantiaca. The selection of a site for oviposition on the host plants was influenced by: (1) cladode condition; (2) height above ground; and (3) shelter from wind during oviposition. Succulent cladodes were the favoured sites for oviposition. The evidence suggests that in C. cactorum, oviposition site selection is largely the net result of a compromise between oviposition behaviour selected for increasing the probability of juvenile survival and oviposition behaviour selected for increasing the probability of laying the full complement of eggs. In addition, environmental and physiological factors such as wind and wing-loading, are thought to place constraints on the range of sites available for oviposition.     

Oviposition in <Emphasis Type="Italic">Heliconius erato</Emphasis> (Lepidoptera,Nymphalidae): how Essential Is Drumming Behavior for Host-Plant Selection?

Quantitative studies on the behavioral events involved in oviposition by phytophagous insects are scant. One of these events is drumming behavior, a rapid extension of forelegs after landing on a host, which remains largely under studied. In this study, quali- and quantitative analyses of Heliconius erato phyllis (Lepidoptera: Nymphalidae) oviposition events and drumming behavior in relation to both preferred (Passiflora misera and P. suberosa) and non-preferred (P. caerulea and P. alata) hosts were performed. For the first time, drumming behavior is described by images made during the butterfly oviposition process. The same set of females was assigned to both single- and multiple-choice tests under insectary conditions, and their behaviors toward each host were recorded on video. The resulting images were analyzed frame by frame. Both frequency and duration of behavioral events related to oviposition varied on preferred vs non-preferred hosts. On preferred hosts, behaviors that were associated with egg deposition (inspecting flight, drumming and abdomen touching) were pronounced; subsequently, oviposition occurred within a few seconds. On non-preferred host plants, behaviors that did not predict oviposition (flying and resting) predominated, and oviposition on these hosts was negligible. Drumming occurred on all plants and resulted in a faster decision-making process on high-quality hosts (prompt acceptance) as well as on lethal hosts (prompt rejection) compared to the host that confers poor larval performance (delayed rejection). Thus, drumming is crucial for decision-making related in host-plant selection by H. erato phyllis, and influences other behaviors involved in the oviposition process.     

黑卵蜂(Telenomus theophilae Wu et Chen)的寄生行为(英语)

本研究采用带电视摄录像系统的体视显微镜观察了黑卵蜂Telenomus theophilae wu et Chen的寄生行为.该种黑卵蜂的寄生系列行为可划分为5个连续的步骤:检查、探测、钻入、产卵和标记.此全过程平均需时17min 20 s,其中钻入和产卵的时间占86.5%.观察结果发现,雌蜂在首次寄生时有一个识别寄主的学习过程.该蜂对野桑蚕Theophila mandarina(Moors)卵的过寄生率,在第一粒寄主卵上是70.6%,而在第4粒卵上则为14.7%,前者为后者的4.8倍.     

Separating the Effects of Experience, Size, Egg Load, and Genotype on Host Response in Trichogramma (Hymenoptera: Trichogrammatidae)

The effects of experience, egg load, and wasp size on the response of four strains of Trichogramma nr. brassicae (Hymenoptera: Trichogrammatidae) to three economically important hosts, Heliothis punctigera (Noctuidae), Phthorimaea opercullela (Gelechiidae), and Sitotroga cereallela (Gelechiidae) were investigated. Experience effects due to rearing host and oviposition were considered in all combinations of host species. Both these effects altered response levels to low-ranked hosts but not to highly preferred hosts. Size was correlated with host response in some strains; larger females took more encounters with a host before accepting it, while egg load was not correlated with number of host encounters. However, egg load, rearing host, and size all affected acceptance of the low-ranked host S. cereallela. Females were more likely to accept this host if they were reared on S. cereallela, had a small size, and had a high egg load. Effects were consistent across strains, although overall acceptance levels differed among strains.     

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.     

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.     

A cyanogenic glucoside of Trifolium repens deters oviposition by the common grass yellow Eurema mandarina

The common grass yellow Eurema mandarina (Pieridae, Coliadinae) widely inhabits Japan, feeds on various fabaceous plants such as silktree (Albizia julibrissin) and uses d ‐pinitol, a cyclitol omnipresent in Fabaceae, as a primary oviposition stimulant. However, E. mandarina has a clear host preference within the Fabaceae; for example, white clover (Trifolium repens) is a nonhost despite containing d ‐pinitol. The present study aims to identify plant chemicals in white clover that inhibit oviposition of E. mandarina. Females lay very few eggs on T. repens foliage and plastic plant models treated with a methanolic extract of the foliage. The foliage extract is fractionated by successive extraction with chloroform, isobutanol and water. None of these fractions induce egg‐laying responses. The aqueous fraction is further separated into four subfractions (Tr‐3‐1 to Tr‐3‐4) by column chromatography. Among these subfractions, females show high egg‐laying responses to Tr‐3‐1, which is known to contain d ‐pinitol. Interestingly, Tr‐3‐2, when mixed with Tr‐3‐1, significantly decreases egg‐laying responses, indicating that it contains oviposition deterrents. Chemical analyses reveal that two cyanogenic glucosides, linamarin and lotaustralin, are the major constituents of Tr‐3‐2. Authentic linamarin does not elicit egg‐laying responses and significantly inhibits female oviposition when mixed with Tr‐3‐1 at the natural concentration. Although these cyanogenic glucosides are reported to synergistically induce oviposition of a coliadine species Colias erate on white clover, we conclude that linamarin acts as an oviposition deterrent for E. mandarina, restricts its host range and regulates their differential host acceptance.     

两种共存网蛱蝶的卵块特征及其雌性成虫对产卵地的选择

对同一网络斑块中金堇蛱蝶(Euphydryas aurinia)和大网蛱蝶(Meiltaea phoebe)雌性成虫的产卵地进行了调查,以确定影响它们斑块质量的因素.结果表明,2种网蛱蝶雌性成虫均选择体积大的寄主植物、周围植被高度低、开放的区域产卵,它们的卵块主要分布在温暖向阳的坡面.金堇蛱蝶的卵块距离农田边缘为3.55±0.33 m (n=246),且集中分布在＜3 m区域内;大网蛱蝶卵块距离农田边缘为7.34±1.53 m (n=25),但在＜3 m区域内的数量少.研究表明,由于这2种网蛱蝶雌性成虫对产卵地要求的特异性,评价它们斑块质量以及对其制定保护管理措施时均应有所不同.