Sobre el comportamiento de alimentacion y nidificacion de Eucraniini (Coleoptera Scarabaeidae: Scarabaeinae)

In this study we report upon the analysis of food relocation and nesting behaviour of some species of the Tribe Eucraniini sensu Zunino, 1985 (Coleoptera: Scarabaeidae), endemic to the arid and semiarid areas of Argentina, namely Ennearabdus lobocephalus (Ennearabdina), Anomiopsoides heteroclyta, Glyphoderus sterquilinus and Eucranium arachnoides (Eucraniina). Observations, carried out either under field conditions [Salta (Cafayate), La Rioja (Chamical), Mendoza (Ñacuñán), Córdoba (Chancaní), San Luis (Juan Jorba, La Punilla)], or in experimental breeding boxes (Chamical, Chancaní and Río Cuarto) placed in natural conditions, allowed us to obtain data concerning the rhythms of adults activity, locomotion behaviour, food manipulation and nest structure. Ennearabdus lobocephalus, the only flying species, very scarce, exploits different kinds of fresh or semifresh excrement and, seemingly, is nocturnal, hypophagic and paracoprid. The Eucraniina, which are apterous or micropterous, diurnal, heliophi- lous, telephagic and telecoprid, feed excusively on dehydrated dung, generally from rodents and camelids, alternatively from domestic herbivores. Food relocation, mainly horizontal, is performed by the specimen using movements and postures which may change depending on the size of the fragment; however, the food relocation pattern is typical and exclusive of the group. Our observations included also some cases of vertical relocation, just beneath the food source, and even rare events of direct feeding without a previous relocation. Differences both in locomotion behaviour and food handling have been observed. The comparison of the obtained data, altough preliminary and incomplete, leads us to hypothesize the occurrence of a remarkable ethological plasticity in Eucranium arachnoides, higher than that of Anomiopsoides heteroclyta and Glyphoderus sterquilinus.