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The tribe Euglossini, in the subfamily Apinae, commonly known as orchid bees or euglossine bees, are the only group of Pollen basket bees whose non-parasitic members do not all possess Eusociality.
Females gather pollen and nectar as food from a variety of plants, and resins, mud and other materials for nest building. Some of the same food plants are also used by the males, which leave the nest upon hatching and do not return.Williams & Whitten, 1983
The chemicals are picked up using special brushes on the forelegs, transferred from there by rubbing the brushes against combs on the middle legs, and finally these combs are pressed into grooves on the dorsal edge of the hind legs, squeezing the chemicals past the waxy hairs which block the opening of the groove, and into a sponge-like cavity inside the hind tibia.Evoy, W. H., & Jones, B. P. (1971). Motor patterns of male euglossine bees evoked by floral fragrances. Animal Behaviour, 19(3), 583-588.
The accumulated "fragrances" are evidently released by the males at their display sites in the forest understory, where matings are known to take place.Eltz et al. 2005Zimmermann et al. 2006 The accumulated volatiles were long believed to be used by males as a pheromone to attract females; however, female attraction to male odors or to orchid fragrances has never been demonstrated in behavioral experiments. Instead, it is now thought that the function of the male odors is to signal male 'genetic quality' to females,Eltz, T., Whitten, W.M., Roubik, D.W., Linsenmair, K.E., 1999. Fragrance collection, storage, and accumulation by individual male orchid bees. J. Chem. Ecol. 25, 157- 176.Eltz, T., Roubik, D.W., Whitten, M.W., 2003. Fragrances, male display and mating behaviour of Euglossa hemichlora: a flight cage experiment. Physiol. Entomol. 28, 251-260. because great effort must be expended by males to collect orchid fragrances and thus only the most fit males could gather complex odor mixes. This would constitute an unusual example of Zahavi's handicap principle, analogous to the male peacock's tail.Zahavi, A., 1975. Mate selection: a selection for a handicap. J. Theor. Biol. 53, 205-214. The relationship between male euglossine bees and volatile chemicals is essentially unique in the animal kingdom.
Scientists use single synthetic compounds as bait to attract and collect males for study; among them are many familiar flavorings and odors considered appealing to humans (e.g., methyl salicylate, eugenol, cineole, benzyl acetate, methyl benzoate, methyl cinnamate), and others which are not (e.g., skatole).Schiestl & Roubik 2004
It is also important to note that resource 'hot spots' wax and wane throughout the year as plants bloom and die, largely due to temporal changes, particularly between the changing of seasons. This often shifts euglossine bee preferences for certain chemicals over others. For Euglossa imperialis, studies have shown that there is a significant trend in chemical preference for cineole during later times in the year as opposed to methyl salicylate. In the local fragrance environment, a shift in the wind direction is another factor which may also cause another fragrance 'hot spot' to be included in the odor plume for euglossine bees.Armbruster, W. Scott. "Within-habitat heterogeneity in baiting samples of male euglossine bees: possible causes and implications." Biotropica (1993): 122-128.
Neotropical orchids themselves often exhibit elaborate adaptations involving highly specific placement of pollen packets (Pollinium) on the bodies of the male orchid bees; the specificity of their placement ensures that Pollination only occurs between orchids of the same species. Different orchid bee males are attracted to different chemicals, so there is also some specificity regarding which orchid bees visit which types of orchid. The early description of this pollination system was by Charles Darwin, though at the time, he believed the bees were females.Darwin & Appleton 1877 Not all orchids utilize euglossines as pollen vectors, of course; among the other types of insects exploited are other types of bees, wasps, flies, ants, and moths.
The male of Eufriesea purpurata is highly unusual among insects in seeking out and collecting large quantities of insecticide. Dressler (1967) discovered E. purpurata collecting aldrin and Roberts (1982) observed them collecting DDTInsect Behavior Mathews and Mathews 2010, p. 352 in huge amounts from houses in Brazil, amounting to several percent of the bee's weight, without suffering any harm from the activity.
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