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Conspecific Larvae (conspecific + larva)
Selected AbstractsDiamondback moth females oviposit more on plants infested by non-parasitised than by parasitised conspecificsECOLOGICAL ENTOMOLOGY, Issue 5 2008YASUYUKI CHOH Abstract 1.,When offered a choice, female diamondback moths (Plutella xylostella) oviposited more eggs on plants with non-parasitised conspecific larvae than on plants with parasitised larvae. 2.,The leaf area consumed by parasitised larvae was significantly lower than that by non-parasitised larvae. However, this quantitative difference in larval damage did not explain the female's ability to discriminate between plants with parasitised and non-parasitised larvae, as females showed an equal oviposition preference for plants infested by higher or lower densities of non-parasitised larvae. 3.,Pupal weight and duration of the larval stage of P. xylostella were independent of whether larvae were reared on plants that were previously infested by either non-parasitised or parasitised larvae. 4.,The larval parasitoid Cotesia vestalis did not distinguish between plants infested by non-parasitised larvae and plants infested by larvae that had already been parasitised by conspecific wasps. 5.,Based on these data, it can be concluded that the moth oviposition preference for plants infested by non-parasitised conspecifics relative to plants infested by parasitised conspecifics was not explained by plant quality or by the attractiveness of plants towards wasps. It is hypothesised that one of the reasons for this preference is avoidance of plants where a relatively high risk of parasitism is expected due to the emergence of parasitoids from the parasitised host larvae. [source] Dispersion of flightless adults of the Asian lady beetle, Harmonia axyridis, in greenhouses containing cucumbers infested with the aphid Aphis gossypii: effect of the presence of conspecific larvaeENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2004Lionel Gil Abstract Most females of the Asian lady beetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), stop laying eggs if conspecific larvae are present. We studied the effect of this inhibition on the dispersion of this insect in a greenhouse containing cucumbers uniformly infested with the aphid Aphis gossypii Glover (Homoptera: Aphididae). In the absence of conspecific larvae, the adults moved around at random, sinuously, and independently. They spent most of their time walking on the ground and only a little time on the aphid-infested plants. When the cucumber plants in one half of the greenhouse had conspecific larvae on them, the whole adult population migrated to the larva-free half of the greenhouse. Consequently, most eggs were laid in that part of the greenhouse which was devoid of larvae. The consequences of this spatio-temporal interaction between larvae and adults for the biological control of aphids is discussed. [source] Host behaviour and exposure risk in an insect,pathogen interactionJOURNAL OF ANIMAL ECOLOGY, Issue 4 2010Benjamin J. Parker Summary 1.,Studies of variability in host resistance to disease generally emphasize variability in susceptibility given exposure, neglecting the possibility that hosts may vary in behaviours that affect the risk of exposure. 2.,In many insects, horizontal transmission of baculoviruses occurs when larvae consume foliage contaminated by the cadavers of virus-infected conspecific larvae; so, host behaviour may have a strong effect on the risk of infection. 3.,We studied variability in the behaviour of gypsy moth (Lymantria dispar) larvae, which are able to detect and avoid virus-contaminated foliage. 4.,Our results show that detection ability can be affected by the family line that larvae originate from, even at some distance from a virus-infected cadaver, and suggest that cadaver-detection ability may be heritable. 5.,There is thus the potential for natural selection to act on cadaver-detection ability, and thereby to affect the dynamics of pathogen-driven cycles in gypsy moth populations. 6. We argue that host behaviour is a neglected component in studies of variability in disease resistance. [source] Evolution of cannibalism and female's response to oviposition-deterring pheromone in aphidophagous predatorsJOURNAL OF ANIMAL ECOLOGY, Issue 5 2009Xavier Martini Summary 1. ,Egg cannibalism by larvae is common in Coccinellidae and is known to be advantageous for the cannibals. Furthermore, larvae of aphidophagous ladybirds usually produce an oviposition-deterring pheromone (ODP), which inhibits oviposition by adult females. It has been proposed that the response to ODP has evolved because of the high costs of cannibalism. However, this has never been formally proved. 2. ,In this paper, we study the theoretical evolution of this system. We first look at the conditions under which cannibalism and the response to ODP can evolve. Subsequently, we examine the occurrence of polymorphism both in the production of larval tracks and in the sensitivity of females to specific pheromones. 3. ,The models predict that the amount of cannibalism should not depend on prey density and that evolution should lead to a continuous increase in cannibalism, and consequently larvae should always cannibalize eggs when possible. In response to the cost of cannibalism, ODP recognition can evolve, so that females avoid laying eggs in patches of prey already occupied by conspecific larvae. The result is an arms race between larvae and adult females, which favours a diversification of ODP pheromones. Our models show that: (i) females should be able to recognize mixtures of hydrocarbons rather than a single molecule; and (ii) females should be more sensitive to the tracks of their own offspring than those of non-related larvae. [source] Cocoon-spinning larvae of Oriental fruit moth and Indianmeal moth do not produce aggregation pheromoneAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2009Zaid Jumean Abstract 1,Mature larvae of the Oriental fruit moth (OFM) Grapholita molesta (Lepidoptera: Tortricidae) and the Indianmeal moth (IMM) Plodia interpunctella (Lepidoptera: Pyralidae) leave their food source in search of suitable pupation sites in which to spin cocoons. These sites are typically well-concealed cracks and crevices within the environment. Such cocooning behaviour is also observed in larvae of the codling moth (CM) Cydia pomonella (Lepidoptera: Tortricidae), which aggregate prior to pupation in response to a pheromone blend produced by cocoon-spinning conspecific larvae. 2,In laboratory experiments, we tested whether cocoon-spinning OFM and IMM larvae produce aggregation pheromones and whether CM larvae are cross-attracted to closely-related OFM larvae. 3,Fifth-instar OFM and IMM larvae were not attracted to, or arrested by, cocoon-spinning conspecifics. Moreover, fifth-instar CM larvae were not cross-attracted to either cocoon-spinning OFM or IMM larvae. 4,Analyses of volatiles released from cocoon-spinning OFM and IMM larvae revealed that both OFM and IMM lack components that are present in the aggregation pheromone of CM larvae. This information may help explain why CM larvae are not cross-attracted to cocooning OFM or IMM larvae. [source] Interactions between the stem-mining weevils Ceutorhynchus napi Gyll. and Ceutorhynchus pallidactylus (Marsh.) (Coleoptera: Curculionidae) in oilseed rapeAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2004Georg Dechert Abstract 1,The rape stem weevil Ceutorhynchus napi Gyll. and the cabbage stem weevil Ceutorhynchus pallidactylus (Marsh.) share the same habitat and food resource within the stems of oilseed rape, Brassica napus L. var. oleifera. Interactions occurring between these two sympatric species on this host were studied under both field and laboratory conditions. 2,The oviposition preference of C. pallidactylus and the within-plant distribution of eggs and larvae were examined in field plots of oilseed rape. Female C. pallidactylus tended to lay their eggs in plants already infested by eggs and larvae of C. napi rather than in uninfested plants. The within-plant distribution of the egg batches of C. pallidactylus did not differ significantly between uninfested plants and those preinfested by C. napi. Ovipositing females of C. napi and C. pallidactylus generally showed a significant preference for plants with larger stem diameter. 3,Laboratory choice tests provided further evidence for the oviposition preference of C. pallidactylus. Females laid significantly more eggs in leaves of plants that had been previously infested by C. napi than in leaves of previously uninfested plants. 4,Larvae of C. pallidactylus showed a significant shift of their feeding niche towards the stem base when feeding in individual plants attacked by both species. This possibly indicates ressource partitioning between C. pallidactylus and C. napi. The within-plant distribution of C. napi larvae was not affected by the simultaneous attack of C. pallidactylus. 5,The size of the head capsule of full-grown larvae of C. napi and C. pallidactylus was not significantly correlated with the diameter of the stem of their host plant or with the number of conspecific larvae within individual plants. [source] Competition as a structuring force in leaf miner communitiesOIKOS, Issue 6 2009Ayco J. M. Tack The role of competition in structuring communities of herbivorous insects is still debated. Despite this, few studies have simultaneously investigated the strength of various forms of competition and their effect on community composition. In this study, we examine the extent to which different types of competition will affect the presence and abundance of individual leaf miner species in local communities on oak trees Quercus robur. We first use a laboratory experiment to quantify the strength of intra- and interspecific competition. We then conduct a large-scale field experiment to determine whether competition occurring in one year extends to the next. Finally, we use observational field data to examine the extent to which mechanisms of competition uncovered in the two experiments actually reflect into patterns of co-occurrence in nature. In our experiment, we found direct competition at the leaf-level to be stronger among conspecific than among heterospecific individuals. Indirect competition among conspecifics lowered the survival and weight of larvae of T. ekebladella, both at the branch and the tree-level. In contrast, indirect competition among heterospecifics was only detected in one out of three species pairs examined. In the field experiment, the presence of a given moth species in one year affected the relative abundance of leaf miner species in the next year. Nevertheless, patterns of competition observed in these experiments did not translate into repulsion among free-ranging leaf miners: conspecific larvae of four leaf-mining species were aggregated on the same trees, shoots and leaves. In contrast, heterospecific larvae were only aggregated at the tree-level. We propose that despite the fact that leaf miners do compete and that such effects extend through time, the incidence and strength of competition is relatively small at realistic densities. Hence, competition will likely be of minor importance in shaping the distribution of leaf miners in a natural setting. [source] | ||||||||||