Some biological aspects of Neotropical genus Caenohalictus Cameron, 1903 (Hymenoptera: Halictidae) in the Andes of Colombia

Caenohalictus (Hymenoptera, Halictidae) is a netropical genus of 57 species occurring from South of America. Few studies have been conducted on biology, behavior and nest architecture. The aim of this study was to research some of these not well known aspects of biology of Andean species of genus Caenohalictus sp., such as behavior, nesting and architecture of nest. 44 nests of Caenohalictus sp. were identified and were constructed for females; also 61 cavities were founded as refuges and protection of males. The nest were tagged and studied for three months in four localities of Colombian Andes. During the monitoring and removal of the nests it was observed that for the Andean bee species of the Caenohalictus sp. genus, they showed a communal sociality and the bees nested forming aggregations in sloping surfaces where was the presence of herbaceous vegetation (grasses) and high sun exposure.. To study the structure of the nests, eight of the 44 nests were excavated, noticing that they had one principal entrance and one to three inputs connected to several tunnels ending in breeding chambers composed of cells of immature individuals in different stages of development. Four activities were observed in females of Caenohalictus (entrances and exits for food searching, vigilance and open and close of principal entrance), and the most important activity was entrances and exits for food searching. Also was obtaining pollen collected for the females and deposited within cells. This pollen corresponds mostly to plants belonging to the Asteraceae. It was also found that some of nests studied were invaded by individuals of Sphecodes sp. which often can parasite nests of individuals of Caenohalictus sp.