The relations of the temperatures of the thorax (TTh), head (Th), and abdomen (Tab) to air temperature (Ta) are described for male euglossine bees attracted to baits. The large, pubescent bees in the genera Eulaema and Eufriesea regulated TTh fairly well, as indicated by the slope of TTh on Ta; Th was distinctly elevated but probably not regulated; Tab was lowest and was most strongly elevated at high Ta, suggesting active heat transfer from the thorax. Euglossa spp., which are smaller and glabrous, regulated TTh somewhat less effectively as a group; here, too, Th was elevated but not regulated; Tab was only slightly higher than Ta and gave no indication of active heat transfer. Measurements of heat-transfer coefficients as a function of size and wind velocity showed that pubescence is a moderately effective insulator of the thorax at wind speeds ≥ 1.0 m s−1. Data on heat-transfer coefficients and body temperatures allowed rough estimation of total heat loss in the field. Heat loss values were consistent with independent measurements of oxygen consumption.