The nesting sites of  Trigona iridipennis Smith at Dharwad were tree trunks and wall cavities. The colonies nested in wall cavities (12 colonies) and tree cavities (5 colonies) were located at the mean height of 192.57 and 222.6 cm from the ground level, respectivily. The mean cavity size in colonies nested  in wall cavities was 132.65 x 143.30 x 165.05 cm of  the 17 colonies observed, 11 had an entrance tube. The length and width of the entrance tube was 96.55 and 3.32 mm in wall cavities and 108.80 and 5.08 mm in tree cavities. The cells were arranged in clusters and surrounded by pollen and honey pots. The mean dimensions of  brood cells, pollen and honey pots were 2.14 x 1.70 mm, 7.26 x 4.49 mm and  7.73 x 5.04 mm in length and width, respectively.