We conducted a laboratory study of the behavioural interactions between larval stages of the lady beetle Coleomegilla maculata lengi Timberlake and an intraguild predator, the lacewing Chrysoperla rufilabris Burmeister. Ladybird susceptibility to predation by third instar C. rufilabris is age-specific and influenced by larval defensive strategies. First and second instars of C. maculata were captured more consistently by chrysopid larvae than third and fourth instars. Young coccinellids generally exhibit escape reactions (dropping, fleeing, retreating) but, do not survive after being caught by lacewings. In addition to escape reactions, older larvae may actively defend themselves by wriggling or biting, even after being pierced. The proportion of physical interactions that resulted in coccinellid death was significantly lower for older instars (<2%) than for first (35%) and second (19%) instars. Capture efficiency by C. rufilabris was related to the coccinellid-chrysopid size ratio. Dropping off the leaves, the most common defensive behaviour displayed by coccinellid larvae, contributed to reduce overall mortality of first instars to a level similar to the one observed for older stages. However, lacewings were able to prevent coccinellid dropping by impaling and holding their prey in the air, or by falling with the ladybirds to the ground where they continued their attack.

made the présentation is in bold characters.

The multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is an invasive species in North America that has a low susceptibility to indigenous natural enemies. We investigated the role of the immune system of H. axyridis in its resistance to North American population of the hymenopteran parasitoid Dinocampus coccinellae Schrank. An ultrastructural study of adult H. axyridis hemocytes under electron and light microscopy identified five different cellular types: plasmatocytes, granular hemocytes I, granular hemocytes II, oenocytoids, and spherule cells. Only granular hemocytes II and plasmatocytes are involved in the nodulation of bacteria and encapsulation of parasitoid eggs. Injection of Sephadex beads in H. axyridis adults induces an innate immune response and results in complete encapsulation of approximate to 28% of the beads after 24 h and 81% after 5 d. When H. axyridis was parasitized by D. coccinellae, we observed a decrease in the encapsulation response, and this pattern was inversely related to the number of parasitoid eggs in the H. axyridis hemolymph. The injection of polydnaviruses by D. coccinellae females and the multiple target hypotheses could both explain the encapsulation rate decreasing with increasing parasitoid egg load. Our results suggest that the immune system of H. axyridis could favor its escape from internal developing natural enemies indigenous to North America.

Under natural conditions, generalist predatory insects have to cope with a variety of potential prey species that are not all equally suitable. Under these circumstances, learning may be adaptive if it allows adjustment to variations in resource quality and availability. Under laboratory conditions, we examined the learning ability and memory in the prey selection process of larvae of the predatory coccinellid Coleomegilla maculata ssp. lengi Timberlake (Coleoptera: Coccinellidae). Using choice tests, we studied prey rejection behaviour of C. maculata fourth instars towards prey of different quality and we also tested the influence of hunger and prior experience with other food types on the prey rejection behaviour of coccinellid larvae. Coleomegilla maculata larvae gradually changed their behaviour and rejected low-quality hosts more frequently, whereas high-quality hosts were nearly always accepted. After 48 h, the learned behaviour appeared to be partially forgotten. Hunger and experience with other food types prior to the test had little effect on the gradual change of behaviour but the quality of the food ingested influenced the initial level of prey rejection. Our results demonstrate that (1) C. maculata larvae can adjust their prey selection behaviour with experience to reject progressively less suitable prey, and (2) previous experience with other prey types can influence their initial preference.

Koinobiont parasitoid females when attacking host species are faced with barriers at various levels, host behavioral defenses represent one of these barriers. We present data of the effects of host behavioral defenses on host preference of larval and adult parasitoid. We quantified the effects of defensive behaviors of the exotic host, Harmonia axyridis (Pallas), and the indigenous host, Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae), on the handling time and attack preference of the indigenous parasitoid, Dinocampus coccinellae Schrank (Hymenoptera: Braconidae). Successful egg development was also recorded as a consequence of host behavioral defense and unsuitability. Female parasitoids were offered in an interspecific choice test, adult or larvae of both H. axyridis and C. maculata , and in an intraspecific choice test, larval and adult stage of H. axyridis . Adult H. axyridis exhibited a greater number of defensive behaviors compared to adult C. maculata or larval H. axyridis resulting in significantly longer handling time by the parasitoid. Our results suggest that host acceptance cues used by the generalist parasitoid D. coccinellae are inadequate to evaluate adult H. axyridis . These results provide support to the hypothesis that H. axyridis represents an evolutionary trap for D. coccinellae .

Successful overwintering of a coccinellid species is partially dependent oil quality of hibernacula, for surviving cold temperatures, for drowning risk, and for avoiding parasitism or infection by pathogens. The multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an introduced species that has spread throughout North America since 1988, over-winters outside and inside houses or artificial structures. Five experiments were conducted during winter 2003-2004 to evaluate winter survival of the invasive H. axyridis compared with the indigenous Coleomegilla maculata lengi Timberlake outside and inside human houses, to assess its contribution to the invasive success of the multicolored Asian lady beetle. We formulated the hypothesis that H. axyridis will survive during winter inside human houses and that no survival would be observed outside ill Quebec, Canada. Survival of H. axyridis ranged from 25 to 53% in different experiments inside houses, whereas no survival was recorded outside. C. maculata did not survive inside houses, but 12.5% of the individuals survived outside. The indigenous species C. maculata had higher proportion of lipids than the invasive species H. axyridis, suggesting that H. axyridis is not physiologically adapted to overwinter in Canada. Selection of human houses as overwintering sites by the multicolored Asian lady beetle may Constitute a "cold-free space," which Could explain its great invasive success in northern regions.

The multicolored Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae), was first reported in southern Canada in 1994.In this study, we examined the status of the ladybeetle in Quebec agroecosystems seven to ten years after its arrival.We integrated the findings from eight independent field studies carried out in pome fruit, grapes, medicinal crops, field corn, sweet corn, sweet pepper, lettuce, and soybean.Nine aphidophagous and 6 coccidophagous coccinellid species were sampled on these crops.Among these aphidophagous species, three invasive (H.axyridis, Coccinella septempunctata and Propylea quatuordecimpunctata) as well as one indigenous species (Coleomegilla maculata lengi) were consistently present.Higher richness was observed in perennial crops, where the 6 coccidophagous coccinellids were almost exclusively present.Higher abundance of aphidophagous coccinellids was observed in field and sweet corn.The multicolored Asian ladybeetle was a dominant species of the coccinellid assemblage in all crops monitored.

The influence of prey mobility and species on prey selection by the coccinellid Harmonia axyridis Pallas was determined under laboratory conditions for two prey species, Hyaliodes vitripennis (Say) and Tetranychus urticae Koch. Prey selection was influenced by prey mobility. In the presence of active prey, the coccinellid selected T. urticae while in presence of immobilized prey, H. vitripennis was preferred. Harmonia axyridis searching time was longer in the presence of active H. vitripennis than in the presence of active T. urticae. Moreover, the coccinellid capture rate was lower for active H. vitripennis caused by effective defensive mechanisms. Prey suitability was affected by prey mobility and species. Immobilized H. vitripennis were the most profitable prey, i.e. induced a shorter developmental time and no mortality. However, active H. vitripennis were not a suitable food source for H. axyridis. Our results suggested that three factors are involved in prey selection by H. axyridis: (i) prey mobility; (ii) prey defensive mechanisms; and (iii) prey species.

We compared biological parameters of the mite predator Hyaliodes vitripennis (Hemiptera: Miridae) reared on live Tetranychus urticae Koch versus two artificial diets used in rearing generalist predators: Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae) and Chrysoperla rufilabris Burmeister (Neuroptera: Chrysopidae). Both coccinellid and chrysopid diet resulted in lower mortality and increased longevity of H. vitripennis, but daily fecundity was greater with the former. The phagostimulant b- sistosterol had the greatest impact on H. vitripennis mortality (lowest) and nymphal weight gain (highest) when added to the coccinellid diet. These results demonstrate that H. vitripennis could be reared on an artificial diet, and suggests that b- sistosterol has phagostimulant properties for this predator.

Previous experiments have demonstrated that green lacewing (Neuroptera: Chrysopidae) adults could be attracted to Weld crops using artiWcial honeydew. To be eVective as a biological control method, such a technique would require that the increase in female abundance translate in an increase egg deposition. An experiment was conducted to evaluate whether the honeydew-feeding females of the green lacewing Chrysoperla ruWlabris (Burmeister) avoid laying eggs in the presence of conspeciWc eggs. The potential risk associated with oviposition in a site already occupied by conspeciWc eggs was also studied. The preference of C. ruWlabris larvae for kin and non-kin eggs and the susceptibility of C. ruWlabris eggs to cannibalism relative to their age was determined. The results demonstrate that females are not reluctant to oviposit in the presence of conspeciWc eggs. Larvae show no preference for kin or non-kin eggs, and lacewing eggs become less susceptible to cannibalism as they age. This indicates that the risk of egg cannibalism by neonate in the Weld may be low. The results are discussed from ecological and biological control points of view. © 2006 Elsevier Inc. All rights reserved.

Le parasitismede lamouche blanche Bemisia tabaci (Gennadius) a été évalué en zone tropicale sèche nicaraguayenne, sur trois cultures maraîchères: tomate, Lycopersicon esculentum Mill., courge, Cucurbita argyrosperma Huber et poivron, Capsicum annuum L. L’objectif du travail était d’identifier les parasitoïdes natifs de B. tabaci et d’évaluer les taux de parasitisme apparent. L’étude a été réalisée en 2001–2002 durant la saison des pluies ainsi qu’au début de la saison sèche 2001. Le nombre de larves de B. tabaci par feuille a été compté hebdomadairement. Pendant la saison des pluies, les parasitoïdes dominants en cultures de courge et tomate sont Encarsia pergandiella Howard et E. nigricephala Dozier. Les taux moyens de parasitisme sont de 17 et 10%pour les cultures de courge et de tomate, respectivement. Sur poivron, les espèces rencontrées sont E. pergandiella, E. nigricephala, E. desantisi Viggiani et Amitus sp. avec un taux de parasitisme de 12%. Pendant la saison sèche, les parasitoïdes rencontrés sur courge sont E. pergandiella et E. nigricephala, avec un taux de parasitisme de 57%. Sur tomate, la seule espèce trouvée, E. pergandiella, est responsable d’un taux de parasitisme de 58%, tandis que sur le poivron, les espèces sont E. pergandiella et E. nigricephala, avecuntauxdeparasitismede 42%.Lenombredeparasitoïdes est resté stabledurant lesdeux saisons d’échantillonnage. Nos résultats suggèrent que le taux de parasitisme apparent est indépendant de la densité de B. tabaci. C’est la première fois que E. pergandiella, E. nigricephala, E. desantisi et Amitus sp. sont mentionnés comme parasitoïdes de B. tabaci au Nicaragua.

Prey vulnerability is a major factor influencing predator preferences. This study evaluated the preference of the glassy-winged mirid bug Hyaliodes vitripennis for two prey types: a slow-moving extraguild prey, the two-spotted spider mite Tetranychus urticae, and a faster intraguild prey, the phytoseiid mite Amblyseius fallacis. Tests were done in the presence of mobile and frozen individuals. Searching and handling time, defensive mechanisms and prey value of the two prey species were also evaluated. Results demonstrated that H. vitripennis had a constant preference for T. urticae over A. fallacis independently of prey mobility. Hence, H. vitripennis preference for T. urticae may be considered as an active predator choice rather than a passive selection. H. vitripennis searching time was longer in the presence of mobile prey than in the presence of the frozen prey regardless of the species. However, prey handling time was not affected by prey mobility. T. urticae did not show any effective defensive mechanisms to avoid the predator attacks while A. fallacis escaped 33.3% of the attacks by fleeing. Defensive mechanisms could reduce attack efficiency of H. vitripennis and increase its foraging costs. Evaluation of prey value showed that T. urticae provided higher weight gain and longer developmental time to H. vitripennis. H. vitripennis preference for T. urticae could be the result of nutritional suitability of this intraguild prey.

In some parasitoid species, the serosa membrane breaks apart at hatching and produces teratocyte cells that assume various functions (immunossupression, secretion and nutrition) mediating host-parasitoid relationships. Teratocyte growth pattern may thus reflect the host suitability for a parasitoid. The teratocyte growth pattern (increase in size and number of teratocytes as a function of time) is studied and used as an indirect measure of fitness to compare the development of the endoparasitoid Dinocampus coccinellae in a marginal host, the coccinellid Harmonia axyridis, and in a suitable host, Coleomegilla maculata. Indirect measures of fitness recorded in both host species confirm that C. maculata is a suitable host for D. coccinellae contrary to the marginal host H. axyridis. According to regression analysis, teratocyte numbers decrease linearly whereas teratocyte size increases linearly with time in the suitable host C. maculata (larvae or adults). In the marginal host, parasitism occurs only in the larval stage where a delay in the parasitoid larval development is observed. Increase in teratocyte size is also highly variable. The teratocyte growth pattern of the parasitoid in the marginal host does not follow the linear model found in the suitable host. Teratocyte growth pattern may be a useful criterion to evaluate host-suitability and host range of parasitoids.

Previous experiments have demonstrated that green lacewing (Neuroptera: Chrysopidae) adults could be attracted to field crops using artificial honeydew. To be effective as a biological control method, such a technique would require that the increase in female abundance translate in an increase egg deposition. An experiment was conducted to evaluate whether the honeydew-feeding females of the green lacewing Chrysoperla rufilabris (Burmeister) avoid laying eggs in the presence of conspecific eggs. The potential risk associated with oviposition in a site already occupied by conspecific eggs was also studied. The preference of C. rufilabris larvae for kin and non-kin eggs and the susceptibility of C. rufilabris eggs to cannibalism relative to their age was determined. The results demonstrate that females are not reluctant to oviposit in the presence of conspecific eggs. Larvae show no preference for kin or non-kin eggs, and lacewing eggs become less susceptible to cannibalism as they age. This indicates that the risk of egg cannibalism by neonate in the field may be low. The results are discussed from ecological and biological control points of view.

Major impacts of biological invasions are widely recognized and underscore the need to understand the relation between life-history traits of invasive species and the invasion process. Growth of juveniles and adult survival of invasive species are key factors in invasion process. Life-history traits that increase juvenile fitness including increased rates of development and behavioral characteristics that facilitate competitive success such as increased predator efficiency and foraging ability may explain invasiveness of a species. Invasion of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in North America provides an opportunity to investigate life-history traits of juveniles of an invasive species. Here, we evaluate both developmental and behavioral traits that may explain the success of H. axyridis by comparing it to an ecologically similar indigenous species Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Three points may contribute to the invasiveness of H. axyridis. First, development of H. axyridis was faster during the 2nd larval instar than C. maculata, a characteristic that may reduce vulnerability at young instars. Second, H. axyridis reached the 4th instar more rapidly than C. maculata. The 4th instar of H. axyridis was also characterized by higher predation efficiency with increased voracity, lethal contact and search efficiency of pea aphids Acyrthosiphon pisum. Finally, surprisingly, a 5th larval instar occured in 33% of the individuals of H. axyridis and was characterized by the same developmental time, but with increased voracity and weight gain compared to 4th larval instars, suggesting an increased fitness of these individuals. These developmental characteristics coupled with increased predation efficiency and behavioral characteristics enhanced the juvenile growth and predatory abilities of this species and may contribute to the invasive ability of H. axyridis.