Dung beetle (Scarabaeus (Pachysoma)) biology and immature stages: reversal to ancestral states under desert conditions (Coleoptera: Scarabaeidae)?
The unique feeding biology of the unusual flightless Namib Desert dung beetle species belonging to Scarabaeus (Pachysoma) MacLeay (Scarabaeidae: Scarabaeinae) has been studied in the past but in this report we document breeding biology, larval feeding and immature morphology for the first time. Females provision burrows with fragments of dry herbivore dung and detritus, in which the larvae develop and on which they feed. This is a novel deviation, and a probable reversal to the ancestral state, from the obligatory brood ball constructed from wet dung in which scarab larvae usually develop. The free-living larvae and pupae have several unique attributes that distinguish them from relatives that develop within the confines of a brood ball and provide additional support for monophyly of the group. Many of these also appear as reversals to a probable ancestral condition. Unique larval characters include a left mandible with two teeth, the absence of a ‘coprine’ hump, small spiracles, and two- or indistinctly three-segmented antennae. Those unique to the pupa are the presence of peculiar prothoracic projections, the absence of lateral tergal supporting projections on the abdomen, and the perpendicular elytra and wings relative to the median bodyline. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 453–460.
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