Would Mothers Relax Their Degree of Selectivity for Supports Suitable for Egg-Laying When the Local Density of Conspecific Females Increases? A Case Study with Three Common Lepidopteran Leaf Miners

Abstract

Selecting suitable supports for egg-laying, among host species and host individuals, as well as between leaves of various qualities within a preferred host, is a major component of prehatching maternal care in herbivore insects. This feature is especially important for those species having a tightly concealed larval stage, such as leaf miners. Yet, increasing density of neighbouring conspecific females may possibly induce ovipositing mothers to relax their degree of selectivity, so as to distribute their eggs more evenly among host leaves and reduce the risk of future scramble competition between larvae within a same leaf. We test this hypothetical prediction for three common leaf-mining moths: Phyllonorycter maestingella, Phyllonorycter esperella, and Tischeria ekebladella. The prediction was supported by none of the three tested species. This suggests that, in these tiny insect species, mothers are either unable to account for the local density of neighbouring conspecific females and/or they have no effective motivation to react accordingly. In addition, this also suggests that host individuals differing by the average quality of their leaves yet exert no differentiated attractivity towards mothers at a distance. In turn, this emphasizes the role of contingent factors in the patterns of spatial distribution of insects' densities.