The relations of the temperatures of the thorax ($T_{th}$), head ($T_{h}$), and abdomen ($T_{ab}$) to air temperature ($T_{a}$) are described for male euglossine bees attracted to baits. The large, pubescent bees in the genera Eulaema and Eufriesea regulated $T_{th}$ fairly well, as indicated by the slope of $T_{th}$ on $T_{a}$; $T_{h}$ was distinctly elevated but probably not regulated; $T_{ab}$ was lowest and was most strongly elevated at high $T_{a}$, suggesting active heat transfer from the thorax. Euglossa spp., which are smaller and glabrous, regulated $T_{th}$ somewhat less effectively as a group; here, too, $T_{h}$ was elevated but not regulated; $T_{ab}$ was only slightly higher than $T_{a}$ 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 es...