Brood parasitism has evolved repeatedly in sweat bees (Halictidae) (Michener, 2000), and in other nestmaking Hymenoptera (bees, wasps, and ants) (see e.g., Wcislo, 1987; Choudhary et al., 1994; Savolainen and Vepsalainen, 2003). However, many parasitic species are relatively rare and therefore little is known of their biology. Megalopta (Augochlorini) is a Neotropical genus of sweat bees, most of which forage under extremely dim light conditions and nest in dead wood (reviewed in Wcislo et al., 2004). It also contains several parasitic species (see Michener, 2000). Megalopta noctifurax Engel, Brooks & Yanega and M. fununculosa Hinojosa-Dy'az & Engel are putative obligate parasites based on morphological features that are associated with parasitic behavior, but there are no rearing records (Engel et al., 1997; Hinojosa-Dy'az and Engel, 2003). A third parasitic species, M. byroni Engel, Brooks and Yanega, was reared from nests of M. genalis Meade-Waldo (Wcislo et al., 2004), and is very rare: only three individuals have been found from .300 nests between 1998 and 2001 (Wcislo et al., 2004). Here we provide notes on reproductive structures that are relevant for understanding the evolution of parasitism, and provide a tentative new host record for M. byroni in Panama' , which was collected from a nest of M. ecuadoria Friese. Engel (2006) selected the synonymous name M. centralis Friese as the name for this species, but a petition to conserve the commonly used name M. ecuadoria will soon be before the International Commission on Zoological Nomenclature for a decision; until a decision is rendered we use the name M. ecuadoria.
