Abstract
Constructions composed of faeces are rare in insects, but occur in certain leaf-beetle clades. Members of the subfamily Cryptocephalinae share a complex behavioural and morphological synapomorphy, involving portable faecal cases that house the immature stages. A maternally initiated egg case is expanded and enlarged through four larval stadia, then sealed to provide a pupal chamber from which adults eventually emerge. We analyse and compare faecal-case architecture in ten taxa of the cryptocephaline genus Neochlamisus, and assess structural variation within a life cycle, between different ‘host forms’ of Neochlamisus bebbianae, and among species. These cases proved to be comprised primarily of faeces, with plant trichomes representing the only common secondary component. General architectural trends reflected variation in shape, faecal texture, and the incorporation and density of trichomes. Deviations of the Neochlamisus case from a simple geometrical gnomon reflect the changing body size of the animal, differential application of faeces, and shifts in the orientation of the carriage of the case. Neochlamisus cases are presumably energetically costly to produce, carry, and maintain, and some adaptive hypotheses of case evolution are proposed. Additionally, literature on case morphology in other camptosomates is reviewed.
Highlights
Faecal construction is one of the oddest behaviours among certain clades of Chrysomelidae
In this study of Neochlamisus cases, we found that the underlying patterns in form and ontogeny indicate highly repetitive construction behaviour
The conservative nature of the architecture and attachment of the egg case suggests a stereotypical behaviour in case construction
Summary
Faecal construction is one of the oddest behaviours among certain clades of Chrysomelidae. Adults and immature stages of species in several subfamilies retain faeces as camouflage, clubs, and protective covers. 190 species) (Seeno & Wilcox, 1982; Reid, 1995, 2000; Farrell, 1998) are commonly referred to as the Camptosomata or ‘case-bearers’, because their species build hard cases of faeces, mixed with anal and oral fluids, around the immature stages (Cockerell, 1891; Lécaillon, 1898; Sharp, 1899; Donisthorpe, 1902; Fiebrig, 1910; Fiori, 1950; Erber, 1968, 1969, 1988; Schmitt, 1988; Reid, 1990, 1991; Olmstead, 1994; Jolivet, 1997; Jolivet & Verma, 2002; Schöller, 2004; Brown & Funk, 2005) (Fig. 1).
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