The orchid bees (Euglossini) are an arresting group of bees, dazzling with iridescent color and extraordinarily long tongues, found only in the New World tropics (Cameron 2004). Known commonly as the orchid bees, they are, as the appellation implies, major pollinators of certain groups of New World orchids. In addition to their complex interactions with members of the Orchidaceae, euglossine bees have been the target of evolutionary investigations of incipient sociality, mimicry, and sexual selection. Their ecological status as important tropical plant pollinators makes them particularly valuable targets for conservation and phylogeographic analysis of population genetic structure. Within Neotropical forests, orchid bees are hard to spot, even though in some locales they compose 25% of the total bee community. Their inaccessibility is due to their solitary habit, speedy flight, and the patchy distribution of floral and nesting resources in tropical forests. Males and females are rarely seen at flowers, many of which may be high in the canopy, and natural nesting sites are even more difficult to find beyond the occasional fortuitous event. Only since the late 1960s, when a group of orchidologists discovered that males could be drawn to chemical baits containing aromatic compounds known from orchids, have the taxonomy and biology of many new species become known. Females, however, are not attracted to chemical baits—only males for the most part visit orchids—so most knowledge of taxonomy, ecology, and population dynamics is based solely on the males. More recently, studies of females attracted to artificial nesting cavities have greatly expanded our knowledge of the nesting biology of several species, yet even the most basic biology of the vast majority of species is still unknown (see however Cameron and Ramirez 2001). While long-term intensive sampling with chemical baits has revealed important new information about the phenology and population dynamics of species and genera, virtually nothing is known of the relationships among species within most genera (Michel-Salzat et al. 2004). Ongoing chemical analyses of orchid fragrances collected and stored in the specially modified hind tibiae of male euglossines have shown that males do not specialize on one or a few orchids but instead collect a species-specific mix from many different orchids [watch a displaying male here]. There are competing hypotheses for why males collect these orchid fragrances, although evidence seems to be building in support of their role in female choice. There are more questions than answers in many aspects of the biology of these bees. Much of the phylogeny is still to be determined, and much of the basic natural history of most taxa remains to be discovered before any deep understanding of their evolution is possible. Our lab has made preliminary investigations of their ecology and relationships and pointed to major gaps in the phylogenetic and behavioral knowledge required to build a foundation for evolutionary studies. Photos: Edward S. Ross.