Cryptic host specificity of an avian skin mite (Epidermoptidae) vectored by louseflies (Hippoboscidae) associated with two endemic Galapagos bird species

Host specificity of vectors is an important but understudied force shaping parasite evolution and the relationship between hosts and parasites. Low vector specificity may allow a vectored parasite to invade new host species, whereas high specificity of vectors may reduce the host range of the parasite and favor specialization. The 'generalist' and widely distributed avian skin mite Myialges caulotoon Speiser (Acari: Epidermoptidae) is unusual because females require an insect vector to complete their life cycle. Myialges caulotoon was previously reported from 2 lousefly (Diptera: Hippoboscidae) species, Olfersia sordida and Icosta nigra, parasitizing flightless cormorants (Phalacrocorax harrisi) and Galápagos hawks (Buteo galapagoensis), respectively, within the Galápagos Islands. This is a surprising distribution, given that the 2 lousefly species involved are relatively host-specific. Mitochondrial DNA sequences revealed 2 reciprocally monophyletic Myialges clades that sorted out perfectly with respect to their vector species, regardless of whether they were in allopatry or sympatry. One clade was restricted to flies of hawks and the other to flies of cormorants. Females of the 2 Myialges groups were also separated consistently by the shape of the sternal surface sclerotization. Mites of hawk flies were more abundant than those of cormorant flies. Within the Myialges clade associated with hawks, genetic differentiation between 2 island populations mirrored its host's patterns of differentiation.     

Polyphagy and primary host plants: oviposition preference versus larval performance in the lepidopteran pest Helicoverpa armigera

Oviposition preference and several measures of offspring performance of Helicoverpa armigera (Hübner) were investigated on a subset of its host plants that were selected for their reputed importance in the field in Australia. They included cotton, pigeon pea, sweet corn, mungbean, bean and common sowthistle. Plants were at their flowering stage when presented to gravid female moths. Flowering pigeon pea evoked far more oviposition than did the other plant species and was the most preferred plant for neonate larval feeding. It also supported development of the most robust larvae and pupae, and these produced the most fecund moths. Common sowthistle and cotton were equally suitable to pigeon pea for larval development, but these two species received far fewer H. armigera eggs than did pigeon pea. Mungbean also received relatively few eggs, but it did support intermediate measures of larval growth and survival. Fewest eggs were laid on bean and it was also the least beneficial in terms of larval growth. Among the host plant species tested, only flowering pigeon pea supported a good relationship between oviposition preference of H. armigera and its subsequent offspring performance. Australian H. armigera moths are thus consistent with Indian H. armigera moths in their ovipositional behaviour and larval performance relative to pigeon pea. The results suggest that the host recognition and acceptance behaviour of this species is fixed across its geographical distribution and they support the theory that pigeon pea might be one of the primary host plants of this insect. These insights, together with published results on the sensory responses of the females to volatiles derived from the different host plant species tested here, help to explain why some plant species are primary targets for the ovipositing moths whereas others are only secondary targets of this polyphagous pest, which has a notoriously broad host range. Handling Editor: Joseph Dickens     

Dispersal in the acanthocephalan Acanthocephalus dirus

In acanthocephalans, dispersal typically occurs when eggs that have been released in the intestines of definitive hosts are expelled with the feces. We examined whether the acanthocephalan Acanthocephalus dirus adopts a strategy of dispersal in which eggs are carried into the environment by gravid females. Using a combination of field surveys and lab-based experiments, we showed that the A. dirus female retained eggs as they passed out of the intestines and that these eggs could develop in intermediate hosts (sediment-dwelling isopods). Lab-based behavioral experiments revealed that the bodies of gravid females were attractive to foraging isopods. We propose that a strategy of egg dispersal could occur in A. dirus in which eggs are carried into the environment by females. This strategy could increase transmission success by dispersing eggs closer to the sediment, rather than in the water column, and by directing the feeding behavior of target hosts.     

The effect of temperature and water quality on the in vitro development and survival of Asellus aquaticus (Crustacea: Isopoda) eggs

The rate of development and degree of survival of Asellus aquaticus eggs outside the marsupium of ovigerous females are affected by water quality and temperature. Eggs were maintained in polluted river water and relatively clean canal water. Developmental rates increase with increased temperature, but survival decreases. Eggs from polluted site ovigerous females survive better in clean water than in polluted water. Eggs from clean site ovigerous females maintained in polluted water have significantly lower survival rates than eggs from the polluted site at all temperatures tested. The developmental rate of clean site eggs is increased significantly in polluted water at 10–25 °C, possibly as a response to the stress imposed upon them.It is suggested that the method outlined might form the basis of a useful bioassay technique for measuring water quality.     

Fly parasitoid Megaselia opacicornis uses defensive secretions of the leaf beetle Chrysomela lapponica to locate its host

Larvae of the leaf beetle Chrysomela lapponica derive a defensive secretion from salicyl glucosides found in the host plant Salix borealis. This secretion protects beetle larvae from some natural enemies, but does not appear to repel parasitoids. We tested the hypothesis that the fly parasitoid Megaselia opacicornis (Diptera, Phoridae) uses the larval defensive secretion of Ch. lapponica in its search for prey. In the field, nearly 30 times more M. opacicornis individuals were caught on leaves coated with sticky resin next to a source of secretion than on control leaves. In the laboratory, M. opacicornis females laid six times more eggs next to a cotton ball soaked in secretion than next to one soaked in water. Fly females also lay more eggs on prey rich in larval secretion than on secretion-poor prey. In the field, removal of defensive secretion from beetle prepupae resulted in a 7.5-fold reduction of oviposition by fly females. Parasitoids were nearly twice as likely to lay eggs on prepupae, rich in secretion, as on pupae, which contain little secretion. Fly offspring reared from beetle prepupae reached a 21% larger body mass than those reared from pupae. Finally, M. opacicornis females avoided host prepupae already parasitized by the tachinid fly Cleonice nitidiuscula, which possess little secretion. These experiments indicate that host plant-derived defensive secretions are used by this parasitoid for host location. Adaptation of parasitoids to use defensive secretions of hosts may selectively favor an increase in diet breadth in specialist herbivores.     

Effects of egg removal on maternal aggression, biogenic amines, and stress indicators in ovigerous lobsters (Homarus americanus)

In many disparate taxa, including crayfish, a freshwater decapod crustacean, the presence of one's offspring has been shown to be an important variable in the level of maternal aggression. Ovigerous American lobsters (Homarus americanus) show a territorial advantage against nonmaternal females, even though no posthatch care is provided. The eggs are attached to the pleopods (swimmerets) throughout embryogenesis. We evaluated the effect of stripping ovigerous H. americanus females of their eggs on maternal territoriality. In one treatment group, maternal females were stripped of all eggs. Twelve days later, including being individually isolated for an additional 48 h in a test tank, each resident was serially intruded upon by 4 non-maternal conspecific females. An identically treated control group of ovigerous female residents was left intact prior to the serial intrusions. Various biochemical parameters of the stripped and unstripped animals were measured before and after the experimental treatment (or control). The behavioral modulators measured were the biogenic amines, octopamine and serotonin, and the stress indicators were a heat-shock protein (HSP70), methyl farnesoate, and crustacean hyperglycemic hormone. The intact ovigerous residents showed a significant territorial advantage over the intruders, whereas the contest outcomes of stripped residents were reduced to chance. The presence of eggs in maternal H. americanus is therefore necessary for the maintenance of the shelter-related territorial advantage. However, no significant differences in any of the biochemical parameters were observed between or within treatment conditions. It appears that these amines are not prominently involved in the mechanism of maternal aggression, and that these changes in territorial defense are not simply due to changes in general stress as a result of stripping the females of their eggs.     

Effects of egg removal on maternal aggression,biogenic amines,and stress indicators in ovigerous lobsters (Homarus americanus)

In many disparate taxa, including crayfish, a freshwater decapod crustacean, the presence of one’s offspring has been shown to be an important variable in the level of maternal aggression. Ovigerous American lobsters (Homarus americanus) show a territorial advantage against nonmaternal females, even though no posthatch care is provided. The eggs are attached to the pleopods (swimmerets) throughout embryogenesis. We evaluated the effect of stripping ovigerous H. americanus females of their eggs on maternal territoriality. In one treatment group, maternal females were stripped of all eggs. Twelve days later, including being individually isolated for an additional 48?h in a test tank, each resident was serially intruded upon by 4 non-maternal conspecific females. An identically treated control group of ovigerous female residents was left intact prior to the serial intrusions. Various biochemical parameters of the stripped and unstripped animals were measured before and after the experimental treatment (or control). The behavioral modulators measured were the biogenic amines, octopamine and serotonin, and the stress indicators were a heat-shock protein (HSP70), methyl farnesoate, and crustacean hyperglycemic hormone. The intact ovigerous residents showed a significant territorial advantage over the intruders, whereas the contest outcomes of stripped residents were reduced to chance. The presence of eggs in maternal H. americanus is therefore necessary for the maintenance of the shelter-related territorial advantage. However, no significant differences in any of the biochemical parameters were observed between or within treatment conditions. It appears that these amines are not prominently involved in the mechanism of maternal aggression, and that these changes in territorial defense are not simply due to changes in general stress as a result of stripping the females of their eggs.     

Sex biased intra-tree oviposition site selection and larval foraging behavior of a specialist herbivore

Heterogeneity in the quality of oviposition and feeding sites within plants can significantly influence the distribution and abundance of herbivorous insects, but remains poorly understood. Field surveys and a manipulative study were conducted to evaluate the influence of variation within the crown of black spruce, Picea mariana (Mill.) B.S.P. (Pinaceae), on adult oviposition and larval feeding behavior of yellowheaded spruce sawfly, Pikonema alaskensis Rohwer (Hymenoptera: Tenthredinidae). Most eggs were laid in the mid to lower crown of 1.5–2 m tall trees. However, most of the few eggs that were laid in the upper crown (i.e., whorl 2) were female. Fourth and fifth instars dispersed acropetally, from the mid and lower to the upper crown, causing high defoliation in the upper crown. Late-instar females were generally more abundant than males on the leader, the most apical shoot on a tree where eggs and early instars rarely occurred, strongly suggesting that more females than males disperse acropetally. This hypothesis was supported in a manipulative experiment, where only 15–20% of larvae in all-male broods, but almost three-quarters of larvae in mixed broods, dispersed to the upper crown. To our knowledge, this is only the second study to explicitly demonstrate preferential allocation of progeny sex through oviposition site selection by a herbivorous insect, and the first study to unambiguously demonstrate sex-biased dispersal by the juveniles of an insect whose adult females can fly. This study emphasizes the important role of intra-plant variation in shaping both oviposition site selection and the dispersal behavior of juvenile phytophagous insects within their hosts, and suggests that sex-biased foraging behaviors may be necessary for some insects to accommodate the respective needs of immature females and males within heterogeneous host plants.     

Effects of larval diet on development rates and reproductive maturation of male and female Mediterranean fruit flies

Abstract Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae) larvae are capable of developing in one of many hosts that may vary greatly in quality. We hypothesized that they will respond to the larval environment in a manner beneficial to their subsequent reproductive performance. Accordingly, we investigated the effects of various larval diets (varying in the amount of protein and sugar they contain) on the size, development time, nutritional status and reproductive maturation (ovarian development and onset of sexual behaviour) of females and males. We found that flies which undergo larval development in artificial host fruit that contain sugar and protein ('protein-fed') were larger, developed faster and emerged with more nutritional reserves than flies that were protein-deprived as larvae. Protein-fed males, regardless of their size, became sexually active before males that developed in hosts with no protein. Protein-fed females produced more mature eggs than protein-deprived ones. Moreover, protein-fed females tended to copulate sooner than females that developed in hosts with no protein. In addition, regardless of female larval diet, females with more mature eggs tended to copulate sooner than females with less mature eggs. In light of these results, the importance of the larval environment for adult reproductive success is discussed.     

The effect of heated effluent on egg production in the estuarine prawn Upogebia Africana (Ortmann)

Egg production of a population of Upogebia africana (Ortmann) in a pond containing water heated by a thermal power station at Knysna, South Africa was compared with that of the population in the adjacent estuary and in two other estuaries. The breeding cycle, proportions of ovigerous females, incubation time for eggs at different temperatures, number of eggs produced, sex ratios, and size-frequency of males and females were all investigated. The number of eggs produced/100 prawns was found to be nearly twice as high in the population exposed to heated effluent as compared with the population in the adjacent estuary. The increase was due to a combination of a change in sex ratio resulting in more females in the population and a greater proportion of larger females in the pond. Since the number of eggs produced/female is positively related to the size of the prawn, large females in warmer water produced more eggs than smaller females in the adjacent estuary. Exposure to heated effluent did not alter the initiation or duration of the breeding season, nor cause precocious maturity; nor did it alter the number of eggs carried per female at various sizes.     

Female reproductive pattern of Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae) in Iskenderun Bay,Eastern Mediterranean

We studied the female reproductive pattern of Callinectes sapidus, which was introduced to the Mediterranean in the 20^th century. We assessed female size at first maturity, fecundity, and fecundity relationship to size in Iskenderun Bay, eastern Mediterranean, Turkey. Samples were collected between July 2014 and June 2015 using bottom trawling at depths ranging from 1 to 50 m. A total of 322 crabs were caught of which 308 (95.7%) were females including 116 ovigerous ones. The minimum carapace width of the mature females was 39.1 mm and the mean carapace width 123.8 mm. The carapace width of ovigerous females varied between 95.1 and 144.5 mm, with a mean of 120.3 mm. The highest number of ovigerous females was observed in July and August. Mean fecundity was 1.91 million (667,950–4,669,853) eggs per female. A weak positive linear relationship between fecundity and carapace width was noted, as well as a high correlation with total egg weight. In the eastern Mediterranean, maturity sizes of females were smaller than those in the native region of the species.     

Effects of recent experience on foraging in tephritid fruit flies

In field-cage studies, we investigated how the foraging behavior of tephritid fruit flies is modified by experience immediately prior to release on host plants. We observed females of a relatively monophagous species,Rhagoletis mendax (blueberry maggot fly), an oligophagous species,Rhagoletis pomomella (apple maggot fly), and a polyphagous species,Ceratitis capitata (Mediterranean fruit fly). Just prior to release on a host plant, the following kinds of stimuli were supplied: (1) single oviposition in a host fruit, (2) contact with 20% sucrose, (3) contact with a mixture of protein food (bird feces and sucrose), (4) contact with water, and (5) a walk over a host-plant leaf. When flies foraged on host plants without resources, search was most intensive (as measured by number of leaves visited) following a single oviposition in fruit, but residence time generally was the same following exposure to sugar, protein, and fruit stimuli.Rhagoletis mendax andC. capitata females visited the fewest leaves following exposure to water or host leaves, whereasR. pomonella foraged equally intensively following exposure to food stimuli, water, or leaves. On host plants containing resources (fruit and protein food), a single oviposition dramatically increased the number of females of all three species that found fruit compared to females that received experience with food, water or foliar stimuli. We found no significant effect of recent brief experience with any of the stimuli on subsequent attraction to protein food. Overall,C. capitata exhibited a higher propensity to abandon host plants than eitherR. mendax orR. pomonella. We suggest that this may reflect adaptations to differences in distribution of host plants in nature, strategies of dispersal, and host range.     

三峡水库秀丽白虾生长与繁殖生物学特征研究

2012 年11 月至2013 年10 月逐月对三峡水库木洞江段秀丽白虾的生长和繁殖生物学特征进行了研究。结果显示秀丽白虾是一年生的虾类, 寿命为1214 个月。雌性个体的平均体长(37.727.92) mm 显著大于雄性(37.086.59) mm, 具有明显的雌雄异形现象。秀丽白虾的渐近体长(L)为59.33 mm, 生长系数(K)是1.6/年, 生长方程为:Lt=59.33-e-1.6(t+0.081)。雌虾繁殖季节从4 月上旬持续至9 月下旬, 繁殖高峰期为4 月中旬至6 月中旬, 由越冬虾和当年虾两个世代的繁殖群体组成。抱卵雌虾的体长为27.0753.71 mm, 平均体长(L50)为37.06 mm。雌雄性比月变化为1.112.36, 平均为1.46, 群体中雌性个体数量显著多于雄性(P 0.001)。绝对繁殖力(FA)为31294 粒, 相对繁殖力(FR)为(11522)粒/g。绝对繁殖力与体长呈幂函数关系(FA=0.0031L2.8632, r=0.72, n=106), 而与体重呈直线关系(FA=104.63W+9.9534, r=0.79, n=106)。卵径(D)平均值为(1215102) m。为合理保护和利用三峡水库秀丽白虾种群资源, 建议加强虾类捕捞管理, 繁殖期间(49 月)禁止捕捞虾类或限制捕捞强度。       

Do Larger Fruits Provide a Partial Refuge for Rose-Hip Flies Against Parasitoids?

The preference of insect herbivores to oviposit into larger structures might be explained by the superior food resource a larger structure offers to herbivore offspring or as an adaptive strategy by the herbivore to protect its offspring against parasitoids, should larger structures provide a partial refuge against parasitoids. We investigated whether larger fruits provide a partial refuge for rose-hip fly (Rhagoletis basiola) offspring against the specialist parasitoid Halticoptera rosae. We tested whether female parasitoids exhibit a preference to land on larger rose-hips into which females of the host fly prefer to oviposit and whether parasitoids are less successful in locating host eggs on large, compared to small, fruits. Female parasitoids showed no clear preference for larger fruits. When searching fruits, they were about equally successful in locating fly eggs on large and small fruits, with a slight, though nonsignificant trend for fly offspring in large fruits to be located more easily. Furthermore, wasps did not require more time to locate host eggs on large fruits than on small fruits, suggesting a nonrandom searching behavior. Consequently, large rose-hips do not provide a partial refuge to fly offspring and the preference of flies to oviposit into larger fruits cannot be explained as an adaptation against parasitoid searching efficiency.     

Local Enhancement of Alighting in the Melon Fly, Bactrocera cucurbitae: Effect of Olfactory, Visual, and Acoustical Stimuli

In studies conducted in Hawaii under both greenhouse and field conditions, we evaluated the propensity of melon fly females, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), to alight on either fruit mimics (agar spheres) or host fruit that were or were not occupied by conspecific resident females. We also examined the extent to which occurrence of local enhancement of alighting found in B. cucurbitae females was affected by a variety of factors such as the presence or the absence of host fruit odor (zucchini or ivy gourd), the number of conspecifics present on a host, the degree of isolation of assayed females from other females prior to testing, and the kinds of stimuli (acoustical, visual, olfactory) emanating from conspecifics present on a host mimic. In addition, we asked whether local enhancement might be operative in the food-foraging behavior of melon flies. We found that in a variety of situations, melon fly females alighted in significantly greater numbers at resources (food, fruit mimics, or host fruit) occupied by conspecific females than at unoccupied resources. Such positive influence of resident conspecific females was more pronounced in greenhouse cage assays when one or two rather than four residents were present on a host mimic (but was more pronounced when four rather than one or two residents were present on a host fruit in a field test), and was more evident when test females were grouped with conspecific females than when test females were isolated from conspecific females for 5 days before testing. Rather than acoustical or olfactory stimuli associated with resident conspecific females, the mere physical presence (visual stimulus) of a motionless dead resident melon fly female provided sufficient stimulation for test females to alight in significantly greater numbers at resources occupied by conspecific females than at unoccupied resources. We consider our findings as good evidence of local enhancement in the melon fly and discuss our results in relation to monitoring tactics for adult melon flies.     

Female-biased density-dependent dispersal of a tephritid fly in a fragmented habitat and its implications for population regulation

The aim of this study was to quantify the rate of dispersal as a response to density in the specialist tephritid fly Paroxyna plantaginis (the main seed predator on its patchily distributed host plant, Tripolium vulgare, Asteraceae). Marked flies were released at three different fly densities in artificial host patches. The individual histories of recaptures were recorded as well as migration between patches and invasion by unmarked flies. The loss of marked flies relative to initial density was analysed using maximum likelihood estimation. Females generally had the highest loss rate. When comparing a density-independent model with a density-dependent model of the loss rate, the density-dependent model won four times out of six for the females but not a single time for the males. A stronger immigration rate of females relative to males supported the suggested female-biased dispersal. This indicates a sit-and-wait strategy for the territorial males and a pre-emptive competition strategy for egg-laying substrates for the females. These results may be of general importance for non-frugivorous tephritid systems with unpredictable and almost ephemeral accessibility to host plants and with a dynamics characterised by a high turnover rate and high attack levels. The study presents a method for measuring the propensity of individuals to leave an area as a response to local density. It is further an example of the consequences individual behavioural responses may have on the population dynamics of a patchy population.     

Effects of meadow suitability on female behaviour in the alpine butterfly Parnassius smintheus

Abstract  1. Many butterfly populations persist in networks of naturally fragmented habitat patches. Movement and reproductive decisions made by adult females are critical to the persistence of these populations because colonisation of extinct habitat patches in the network requires emigration of fecund adult females from their natal meadow and their subsequent establishment in the extinct patch.
2. Movement and oviposition behaviours of mated Parnassius smintheus females released in suitable meadows (a good- and a poor-quality meadow) and an unsuitable meadow were compared, to determine whether adult females consider meadow suitability for their offspring despite frequent oviposition events off the larval host plant.
3. Bootstrap and correlated random walk analyses of female step lengths and turn angles demonstrated that females flew more randomly in the unsuitable meadow than in the suitable meadows. Although females tended to turn the sharpest angle between landing sites in the good-quality meadow, and fly the smallest distance between landing sites and displace the smallest distance from the release site in the suitable meadows, no significant differences were detected in turn angle, step length, and dispersal rates between suitable and unsuitable meadows.
4. Results from female flight observations and a caged oviposition study suggest that females lay significantly more eggs in suitable habitat than in unsuitable habitat despite not ovipositing on the host plant, and support the above findings.
5. Movement and oviposition behaviours of adult female P. smintheus promote their retention within meadows that can support their offspring.     

Are individuals from thelytokous and arrhenotokous populations equally adept as biocontrol agents? Orientation and host searching behavior of a fruit fly parasitoid

Hymenopteran parasitoids generally reproduce by arrhenotoky, in which males develop from unfertilized eggs and females from fertilized eggs. A minority reproduce by thelytoky, in which all-female broods are derived from unfertilized eggs. Thelytokous populations are potentially of interest for augmentative biological control programs since the exclusive production of females could significantly lower the costs of mass rearing. Behavioral traits are a major component of parasitoid efficacy. Here, we examined orientation and host searching behavior in thelytokous and arrhenotokous populations of the fruit fly parasitoid Odontosema anastrephae Borgmeier (Hymenoptera: Figitidae). Orientation behavior to various odorant sources was studied in a two-choice olfactometer. No major differences were found between thelytokous and arrhenotokous wasps for this behavior. However, when host-searching behaviors were analyzed, some differences were found. Thelytokous females arrived sooner, foraged longer, and remained longer on non-infested guavas than arrhenotokous females. Individuals of both forms exhibited similar stereotyped behavioral sequences vis-à-vis guava treatments, with only slight deviations detected. Our results suggest that individuals from selected thelytokous and arrhenotokous O. anastrephae populations have similar abilities to search for tephritid larvae, supporting the use of thelytokous strains for augmentative releases.     

Oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens

We assessed the role of visual and olfactory cues on oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae). In a field survey, we evaluated the stage of susceptibility of field‐grown tomatoes by monitoring N. cyanescens infestations from fruit‐setting up to harvest, in relation to post‐flowering time, size, and visual properties of fruit. In two‐choice laboratory experiments, we tested the degree to which females use visual and olfactory cues to select their host plant for oviposition. In addition, we investigated the ability of flies to avoid fruit already infested by conspecific eggs or larvae, and the influence of natal host fruit on oviposition preference. Neoceratitis cyanescens females preferentially lay their eggs in small yellow‐green unripe fruit (2–3.5 cm diameter, 10–21 days post‐flowering). Damage to fruit was significantly affected by brightness and size properties. In laboratory experiments, females chose to lay their eggs in bright orange rather than yellow domes. On the sole basis of olfactory stimuli, females showed a significant preference for unripe vs. ripe host fruit, for unripe fruit vs. flowers or leaves, and for host vs. non‐host fruit (or control). However, colour interacted with odour as females dispatched their eggs equally between the yellow dome and the bright orange dome when unripe fruit of tomato was placed under the yellow dome vs. ripe fruit under the bright orange dome. When offered real ripe and unripe tomatoes, females preferred unripe tomatoes. Females significantly chose to lay eggs in non‐infested fruit when they were given the choice between these or fruit infested with larvae. In contrast, recent stings containing eggs did not deter females from laying eggs. Rather, they could have an attractive effect when deposited within <1 h. Regardless of their natal host plant, tomato or bugweed, N. cyanescens females laid significantly more eggs in a dome containing bugweed fruit. However, 15% of females originating from tomato laid eggs exclusively in the dome with tomato, against 3% of females originating from bugweed.     

Antixenosis and larval and adult dispersal in the Mediterranean corn borer,Sesamia nonagrioides,in relation to Bt maize

Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae) is a key pest of maize [Zea mays L. (Poaceae)] and a main target of Bt maize in the Mediterranean area. To choose the most suitable non‐Bt refuge strategy for preventing or delaying resistance development in this maize borer, we examined its biology and behaviour. No antixenotic effects were found on numbers of eggs and egg batches per plant in choice (Bt vs. non‐Bt plants) and no‐choice assays. However, a greater ratio of young larvae dispersed from Bt than from non‐Bt plants. In addition, larvae that hatched on Bt plants tended to disperse more than those that hatched on non‐Bt plants, particularly during young growth stages. Many adults, especially females, could fly at least up to 400 m, as was found in a dispersal study with rubidium‐marked adults. The stimulation of larval dispersal by the Bt trait and the dispersal capacity of adults might compromise the efficacy of seed mixtures as an insecticide resistance management strategy.