The most beautiful and remarkable of all the bees are the species of _Euglossa_. This genus is peculiar to Tropical America, and derives its name from the great length of the proboscis, which in some species surpasses that of the body. The colours in _Euglossa_ proper are violet, purple, golden, and metallic green, and two of these are frequently combined in the most harmonious manner; the hind tibia is greatly developed and forms a plate, the outer surface of which is highly polished, while the margins are furnished with rigid hairs. Very little is known as to the habits of these bees; they were formerly supposed to be {35}social; but this is doubtful, Bates having recorded that _E. surinamensis_ forms a "solitary nest." Lucas concluded that _E. cordata_ is social, on the authority of a nest containing "a dozen individuals." No workers are known. The species of _Eulema_ have a shorter tongue than _Euglossa_, and in form and colour a good deal resemble our species of _Bombus_ and _Apathus_. The group Dasygastres includes seven European genera, four being British (_Chelostoma_ being included in _Heriades_). The ventral surface of the hind body is densely set in the females with regularly arranged hairs, by means of which the pollen is carried. In many of the Dasygastres (_Megachile_, _e.g._) the labrum is very large, and in repose is inflected on to the lower side of the head, and closely applied to the doubled-in tongue, which it serves to protect; the mandibles then lock together outside the labrum, which is thus completely concealed. This group includes some of the most interesting of the solitary bees. [Illustration: Fig. 18.—_Euglossa cordata_, ♂. Amazons. A, The Insect with extended proboscis; B, outer face of hind tibia and tarsus.]