Beetles (Coleoptera) of Peru: A Survey of the Families. Chrysomelidae: Bruchinae Latreille, 1802

Abstract

Diversity in Peru: 3 tribes, 17 genera, 55 species (8 new records). Recognition: Bruchines are popularly known as seed weevils or seed beetles because the larvae enter seeds, where they consume the insides and then form a pupation chamber. While not true weevils (e.g., superfamily Curculionoideae), their name is derived from the habit of feeding within seeds as larvae and the tapering of the head toward the mandibles that loosely resembles a rostrum. This latter feature allows emerged adults to complete excision of an exit hole from host seeds. Adults have a compact body with small head, eyes usually emarginate, usually enlarged metafemora, and an exposed pygidium. Instar 1 larvae have a transverse toothed dorsal prothoracic plate that is unique among beetles. Larvae are thick, curved, and soft-bodied; some larvae have legs or are apodous. While the presence of a pygidium, emarginate eyes, and enlarged metafemora are generally sufficient to distinguish adults of the subfamily, Kingsolver (2004) provides further characters for definition of the group. Habitat: Since females lay eggs on fruits or seeds, and successful development to adult from egg depends on successful consumption of seeds, the best method for collecting bruchines is by rearing them from seeds. However, significant insights into the biology of Peruvian Bruchinae may be found through non-conventional examination of host plants as at least one undescribed South American species is reported to make bud galls in flowering twigs (Bridwell, 1952), and a second (Merobruchus bicoloripes (Pic, 1927)) regularly lays its eggs on leaflets or petioles and first instar larvae crawl to pods before burrowing (Teran and Muruaga de L’Argentier, 1981). Specimens are often collected using other more traditional methods, including sweep-netting, light traps, flight intercept traps, or litter funnels, but in much lower numbers, much less predictably, and of course without the associated ecological information. Numerous published host records from Peru involve this family (Bridwell, 1942; Kingsolver, 1968a, 1991; Johnson, 1990), and many specimen records involve species that are known to associate exclusively with this family (Johnson, 1968; Johnson et al., 1989; Kingsolver, 1968b, 1972; Kingsolver and Whitehead, 1974; Pierce, 1915). Other prominent associations in Peru involve the Convolvulaceae (Megacerus Fahraeus en Schoenherr, 1839; Teran and Kingsolver, 1992), and Arecaceae (Pachymerini; Nilsson and Johnson, 1993; Delobel et al., 1995). In addition, while no rearings from Malvaceae have been reported from Peru, at least one species known to associate exclusively with this family (e.g. Amblycerus simulator (Jacquelin-Duval,