Development of the Ovary and Mating Behavior in Phanaeus1,2

Abstract

In Coleoptera the reduction of the ovaries reaches its extreme in the subfamily Scarabaeinae: a single ovary consisting of a single ovariole. So far a single ovariole has been observed in 38 species of the subfamily (representing 19 genera), of which 11 are considered in this study. Extreme reduction of the ovaries is probably related to the high degree of efficiency of the complex nesting behavior of dung beetles. The developmental histology and anatomy of the female reproductive system of Phanaeus daphnis Harold and Phanaeus mexicanus Harold (Coleoptera: Scarabaeidae) is described beginning 45 days before adult emergence to just after copulation. The musculature of the vagina is described and related to a proposed mechanism whereby the genital orifice is opened and closed, the vagina dilated and contracted and spermatozoa forced into spermatheca. The spermatophore is described for the first time, as well as the process by which it disintegrates in the vagina. In Phanaeus copulation is not related to the bisexual cooperation in the excavation and provisioning of feeding galleries. Copulation occurs once, releasing oviposition and nidification behaviors, which occur later. The male seems to provide a stimulus for nidification although the female can nest alone. In the presence of a male, a female prepares more brood balls per unit time. There is also an increase in brood ball construction if more than one pair cohabit the same terrarium in the laboratory. Copulation is described in detail as well as the physiological and behavioral changes it elicits in the female.