Functional anatomy of the vesica in Eugnosta magnificana (Insecta: Lepidoptera: Tortricidae)

Abstract

This study is the first attempt to elucidate the detailed function of the internal musculature of the phallus in Lepidoptera with respect to complementary female structures. Based on the examination of Eugnosta magnificana, a leaf-roller species with a large elaborate vesica (endophallus), the attachment points of the muscle bundles are described and their putative function is discussed. Some parts of the vesica (two large diverticula with cornuti) are not everted in living specimens, though their artificial eversion is possible after maceration with KOH. Direct observation of everted vesica of living moths showed that its large diverticula are capable of at least two movements: forth-and-back and flexion–extension. Hypothetical position of the internal male and female genitalia during copulation is proposed. It appears that the corpus bursae consists of two compartments with different functions: anterior for spermatophore digestion and posterior for interaction with the vesica. Some evidence of a stimulating function by non-deciduous cornuti was found.