Inter-and intra-specific effects of the mandibular gland secretion of larvae of the Indian-meal moth, Plodia interpunctella

ABSTRACT. The effects of the mandibular gland secretion of larvae of Plodia interpunctella (Hübner) on the behaviour of conspecific larvae and on its parasitoid, Nemeritis canescens (Gravenhorst) were studied in open chambers and in an olfactometer. The secretion is deposited in the form of droplets on the silk while it is being spun, and as irregular patches on the substratum. Plodia larvae presented with a choice between fresh food and food contaminated with mandibular gland secretion chose fresh food. Those provided with contaminated food only, chose this in preference to starvation. The secretion also caused 'attraction' and stimulation of oviposition movements in female Nemeritis , leading to increased parasitization. The stimulatory effect of the droplets was remarkably persistent and could be detected after storage for at least 5 years at room temperature as well as at 4°C or -7°C. Chemical analysis indicated the presence of two components, the major with an Rf value of 0.6 (empirical formula C₂₄H₄₀O₄), and the other with an Rf value of 0.8 (empirical formula C₂₂H₃₈O³).