Family 21, Nemestrinidæ.—These insects are chiefly inhabitants of tropical climates like the preceding family. They are generally of a black colour, sometimes with red legs. They suck the nectar of flowers through a long proboscis, but nothing is yet known of their transformations.
Fig. 139.—Xylophagus Ater (Mag.)
Fig. 140.—Ceria Conopsoides (Mag.)
Family 22, Bombyliidæ.—The Bee Flies belong to this family. They are small or middle-sized insects, densely clothed with hairs. They are exceedingly active insects with long tongues, with which they suck honey from flowers. Their larvæ are often parasitic in their earlier stages on other insects.
They are very useful in North America by keeping down the number of locusts, in the egg capsules of which the larvæ feed.
Two species, Bombyliis major and B. medius, are common in this country, and may often be seen in gardens and open spaces in woods during the spring and summer months.
Family 23, Therevidæ.—This family is a very numerous one, especially those of the typical genus Thereva. They are slender, middle-sized black insects, and their bodies are generally covered with hair. They are generally found in the neighbourhood of bushes and trees.