Adaptation to Seed-Feeding in Ground Beetles (Coleoptera: Carabidae: Harpalini) of South Venezuela

Seed-feeding communities of ground beetles (Carabidae) were examined on fruit falls of two tree species in the upper Orinoco region of Venezuela: Miconia poeppigii (Melastomataceae) and Goupia glabra (Celastraceae). Two ground beetle species of the genus Notiobia and one species of Selenophorus reproduced on fruit fall of M poeppigii. Two other species of Notiobia reproduced on fruit falls of G. glabra though both fruit fall sites were in the direct vicinity. Larvae of all five ground beetle species were examined. The structure of the larval mandible is specialized and plays an important role in the adaptation to feeding on a specific fruit in the genus Notiobia. The apical part of the mandible maintains about the same length during all three larval instars in seed feeders. In contrast, the length of the mandibular apex increases about 30-50% from instar to instar in carabid larvae which are polyphagous or generalized predators. The relation head width: length of mandible varies greatly from instar to instar in seed-feeding Notiobia species (40-66%). It is nearly constant in generalized predators (Platynus assimilis: 12%) and other phytophagous larvae as Zabrus tenebrioides or Amara spp.