Male Body Size and Mating Success and Their Relation to Larval Host Plant History in the Moth Rothschildia lebeau in Costa Rican Dry Forest

Individual Variation in Male Pheromone Production in Xylocopa sonorina Correlates with size and Gland Color

Sex pheromones are species-specific chemical signals that facilitate the location, identification, and selection of mating partners. These pheromones can vary between individuals, and act as signals of mate quality. Here, we investigate the variation of male pheromones in the mesosomal glands of the large carpenter bee Xylocopa sonorina, within a Northern California population. We tested the hypothesis that morphological traits are correlated with the observed variation in chemical blend composition of these bees. We also conducted behavioral assays to test whether these male pheromones act as long-range attractants to conspecifics. We found that larger males with darker mesosomal glands have a higher pheromone amount in their glands. Our analysis also suggests that this pheromone blend functions as a long-range attractant to both males and females. We show that both male body size and sexual maturation are important factors influencing pheromone abundance, and that this pheromone blend acts as a long-range attractant. We hypothesize that this recorded variation in male pheromone could be important for female choice.

Size-dependent flight capacity and propensity in a range-expanding invasive insect

For capital-breeding insects, all resources available for adult metabolic needs are accumulated during larval feeding. Therefore, body size at adult eclosion represents the total energetic capacity of the individual. For female capital breeders, body size is strongly correlated with lifetime fecundity, while in males, body size, which correlates with fitness, is less understood. In capital-breeding species with wingless, flightless, or dispersal-limited females, flight potential for male Lepidoptera has important implications for mate-finding and may be correlated with body size. At low population densities, failure to mate has been identified as an important Allee effect and can drive the success or failure of invasive species at range edges and in species of conservation concern. Th capital-breeding European subspecies of Lymantria dispar (L.), was introduced to North America in 1869 and now ranges across much of eastern North America. In L. dispar, females are flightless and mate-finding is entirely performed by males. We quantified male L. dispar flight capacity and propensity relative to morphological and physiological characteristics using fixed-arm flight mills. A range of male body sizes was produced by varying the protein content of standard artificial diets while holding other dietary components constant. Wing length, a proxy for body size, relative thorax mass, and forewing aspect were all important predictors of total flight distance and maximum speed. These results have important implications for mate-finding and invasion dynamics in L. dispar and may apply broadly to other capital-breeding insects.

Intraspecific variation of body size in fleas: effects of host sex and flea phenology

We investigated the effects of host sex and flea phenology (estimated as periods of high versus low abundance) on individual body size in four fleas of small mammals. Amalaraeus penicilliger and Ctenophthalmus uncinatus are ectoparasites of the bank vole Myodes glareolus, whereas Doratopsylla dasycnema and Palaeopsylla soricis are ectoparasites of the common shrew Sorex araneus. We found significant effects of host sex and phenology on the body size of all flea species, although there was no general trend in the directions of these effects. Larger A. penicilliger were found on female hosts, whereas larger P. soricis were found on male hosts. In the remaining species, larger fleas were collected from male hosts during periods of high abundance (male C. uncinatus and female D. dasycnema) and from female hosts during periods of low abundance (male C. uncinatus). Regarding phenology, larger fleas were recorded during periods of either high (A. penicilliger, C. uncinatus, D. dasycnema) or low (C. uncinatus, P. soricis) abundance, but this depended on flea and/or host sex. We conclude that the directions of the host sex and phenology effects varied between flea species. Furthermore, the direction of the host sex effect was mediated by the effect of phenology and vice versa.

Host gender and offspring quality in a flea parasitic on a rodent

The quality of offspring produced by parent fleas (Xenopsylla ramesis) fed on either male or female rodent hosts (Meriones crassus) was studied. The emergence success, duration of development, resistance to starvation upon emergence and body size of the flea offspring were measured. It was predicted that offspring of fleas produced by parents that fed on male hosts (i) will survive better as pre-imago, (ii) will develop faster, (iii) will live longer under starvation after emergence and (iv) will be larger than offspring of fleas fed on female hosts. The emergence success of pre-imaginal fleas was relatively high, ranging from 46.9% to 100.0% and averaging 78.4±3.0%, and was not affected by host gender. The duration of development of pre-imaginal fleas depended on the gender of the host of parents and differed between male and female offspring, with female fleas developing faster. Furthermore, male fleas developed faster if their parents fed on female rather than on male hosts, whereas no difference in the duration of development between host genders was found in female fleas. The time to death under starvation did not depend on the gender of either the flea or the host. A newly emerged flea, on average, lived 31.9±1.0 days without access to food. The relationship between host gender and body size of male flea offspring was the only effect that supported the predictions. An increase in body size in male fleas could increase their mating success and, ultimately, their fitness.