Behavioural ecology of a hilly population of Timarcha pimelioides Schäffer (Coleoptera: Chrysomelidae)

The study concerns the behavioural ecology of a hilly Sicilian population of Timarcha pimelioides. It is an insect inhabiting a wide range of habitats from dune systems to low mountains in Sicily and southern Italy. Within 28 months we analysed the feeding preference and the reproductive behaviour, and reconstructed the life cycle of the species. The typical oligophagy of the genus Timarcha reaches its extreme in the studied population. Both adults and larvae are strictly monophagous on Galium aparine, a herbaceous annual plant belonging to the family Rubiaceae. The obliged association between this population of T. pimelioides and its host-plant differs from what has been described for another population of the same species living in a coastal dune system of southern Sicily (Costa et al., 1983): in the latter case there is a double diet, adults feeding on Plantago coronopus (Plantaginaceae) and larvae on Crucianella maritima (Rubiaceae). Particular novelty has not emerged in the analysis of the reproductive behaviour, but an interesting outcome has regarded the oviposition: female lays a first egg without any protection before the laying of some egg groups, each of which sprinkled with a protective secretion. Exclusive links between mono- or oligophagous insect species and different host-plants could spur further investigations and closer examination of the co-evolutionary mechanisms. Moreover, the understanding of the unprotected first egg laid deserves special attention.