Search

Wild birds are hosts of Culicoides from as early on as the nesting stage when constrained to their nests. However, the environmental factors which determine the abundance and composition of Culicoides species within each bird nest are still understudied. We sampled Culicoides from Eurasian blue tit (Cyanistes caeruleus) nests found in 2 types of forests located in southern Spain. Firstly, we monitored the abundance of Culicoides species in bird nests from a dry Pyrenean oak deciduous forest and a humid mixed forest comprising Pyrenean and Holm oaks throughout 2 consecutive years. During the 3rd year, we performed a cross-fostering experiment between synchronous nests to differentiate the role of rearing environment conditions from that of the genetically determined or maternally transmitted cues released by nestlings from each forest. We found 147 female Culicoides from 5 different species in the birds' nests. The abundance of Culicoides was higher in the dry forest than in the humid forest. Culicoides abundance, species richness and prevalence were greater when the nestlings were hatched later in the season. The same pattern was observed in the cross-fostering experiment, but we did not find evidence that nestling's features determined by the forest of origin had any effect on the Culicoides collected. These results support the notion that habitat type has a strong influence on the Culicoides affecting birds in their nests, while some life history traits of birds, such as the timing of reproduction, also influence Culicoides abundance and species composition. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify resistance of tolerance type in Citrus and Poncirus genotypes towards the citrus leafminer (CLM), Phyllocnistis citrella. The quantitative variables leaf and shoot lengths, leaf width, number of larvae and new shoots, and fresh and dry shoots weights, and qualitative variables associated with foliar damage were evaluated in six Citrus-related genotypes infested with CLM. In preliminary trials with lime Rough lemon (C. jambhiri), the variables that best discriminated the infestation effect of CLM were established as the numbers of larvae and new shoots per plant together with the percentages of partially rolled leaves (PRL), rolled leaves (RL) and total damage (TD = RL + PRL). In subsequent tests with all six genotypes, the variables new shoots per plant, percentage of attacked but not rolled leaves (ANRL), RL and TD were found to be significant. Trifoliata Limeira (P. trifoliata) and hybrid C × R4 (C. sunki × P. trifoliata) presented the lowest percentages of RL and TD and the highest values of ANRL. A cluster analysis was performed considering all the variables analyzed and the most tolerant genotypes for CLM, namely hybrids C × R4, C × R315 (C. sunki × P. trifoliata), M × P222 [C. sinensis × Tangor Murcott (C. reticulata × C. sinensis)] and Trifoliata Limeira (P. trifoliata) were grouped apart from the less tolerant genotypes Sunki mandarin (C. sunki) and lime Rough lemon. In conclusion, genotypes Trifoliata Limeira and its hybrid C × R4 are the most tolerant to CLM. [ABSTRACT FROM AUTHOR]

The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8- heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound. [ABSTRACT FROM AUTHOR]

We presented the tachinid fly Exorista japonica with moving host models: a freeze-dried larva of the common armyworm Mythimna separata, a black rubber tube, and a black rubber sheet, to examine the effects of size, curvature, and velocity on visual recognition of the host. The host models were moved around the fly on a metal arm driven by motor. The size of the larva, the velocity of movement, and the length and diameter of the rubber tube were varied. During the presentation of the host model, fixation, approach, and examination behaviours of the flies were recorded. The fly fixated on, approached, and examined the black rubber tube as well as the freeze-dried larva. Furthermore, the fly detected the black rubber tube at a greater distance than the larva. The rubber tube elicited higher rates of approach and examination responses than the rubber sheet, suggesting that curvature affects the responses of the flies. The length, diameter, and velocity of host models had little effect on response rates of the flies. During host pursuit, the fly appeared to walk towards the ends of the tube. These results suggest that the flies respond to the leading or trailing edges of a moving object and ignore the length and diameter of the object. [ABSTRACT FROM AUTHOR]