Phenotypic plasticity of pigmentation and morphometric traits in Pnigalio soemius (Hymenoptera: Eulophidae).

Species of the genus Pnigalio Schrank are ectoparasitoids on several pest insects. Most species are polyphagous parasitoids of lepidopteran and dipteran leafminers. Despite their potential economic importance, information on intraspecific phenotypic variability is insufficient. Pnigalio soemius (Walker) was reared at five different temperatures (10, 15, 20, 25, 30 degrees C) on mature larvae of one of its natural hosts, Cosmopterix pulchrimella Chambers (Lepidoptera: Cosmopterigidae), to investigate the influence of temperature on size, colour and other morphological traits, and to measure the range of variation of several characters. Thermal developmental reaction norms, which represent the effect of temperature during growth and development on the value of some adult traits, were produced. The results confirmed the influence of temperature on numerous characters and that these characters had a larger range of variation than realized previously in the construction of taxonomic keys to species. In particular, the number and position of the costulae on the propodeum and colour of the gaster were affected by rearing temperature.