Subfamily Scarabaeinae Research Articles

Two nesting behaviours and life history of a subsocial African dungrolling beetle, Scarabaeus catenatus (Coleoptera: Scarabaeidae)

Nesting behaviour of a large-sized dung beetle, Scarabaeus catenatus (Gerstaecker), was observed at the Tsavo West National Park, south-eastern Kenya. Although this species is taxonomically a member of a dung-roller group (that is, subfamily Scarabaeinae), it had not only a rolling behaviour but also a tunneller behaviour for nesting. In the former case, the scarab rolled a chunk or a ball of dung some distance (0·5–15·5m) away from the dung pat and buried it under the ground. In the latter case, it dug a tunnel near the dung pat (0–1 m) and transported several pieces of dung into the burrow. In both cases, brood nests were completed by a female alone or by male-female co-operation. Four days after dung burial, the female made one to four brood balls out of buried dung, in each of which she deposited an egg. On the other hand, the male left the nest soon after the female completed oviposition. Even after oviposition, the female stayed in the nest and cared for her progeny until they emerged. This indicates that S. catenatus is subsocial. A major source of offspring mortality was likely to be predation by driver ants (Dorylus sp.). Most females seemed to breed one time in each of two or more successive rainy seasons.

Development of the Ovary and Mating Behavior in Phanaeus1,2

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.

Book Notices

The natural history of dung beetles of the subfamily Scarabaeinae (Coleoptera, Scarabaeidae). By Gonzalo Halffter and Eric G. Matthews.Hymenoptera of America north of Mexico: Synoptic catalog. 2nd Supplt. Edited by K. V. Krombein and B. D. Burks.