_Family 13, Xylophagidæ._--The _Xylophagidæ_ are thick-looking insects. The head is as broad as the thorax. The legs, which are long and slender, are quite naked. The _larvæ_ live in rotten wood, and the flies may often be seen at rest on the trunks of trees. [Illustration: Fig. 134.--Sargus Cuprarius (Mag.)] _Family 14, Cœnomyiidæ._--In this family the head is narrower than the thorax; otherwise they closely resemble the previous family. The typical European species is _Cœnomyia ferruginea_, which measures about three-quarters of an inch in length, and in colour varies from rusty-yellow to black. The _larvæ_ feed inside the trunks of rotten poplars. _Family 15, Stratiomyiidæ._--These are rather slender flies, varying from half to one inch in length. They are usually found resting on low plants. Many species frequent cow-dung and manure, etc. Several kinds exhibit a metallic coloration, others are black, often more or less varied with white or yellow. [Illustration: Fig. 135.--Chrysops Cæcutriens (Mag.)] _Family 16, Acanthomeridæ._--The _Acanthomeridæ_ are met with principally in America. The typical species, _Acanthomera picta_, is found in Brazil, and measures more than an inch in length. It used formerly to be largely used in the manufacture of pomade. _Family 17, Tabanidæ._--The _Tabanidæ_ are broad-looking insects. The _larvæ_ usually live in damp earth. The females of these species live on the blood of animals. The best-known species is the Gad Fly (_Tabanus bovinus_), which measures more than an inch in length, and is particularly troublesome to cattle in hot weather. It is blackish above, and reddish beneath and on the sides of the abdomen. The Clegg Fly (_Hæmatopota pluvialis_) also belongs to this family. It is a dingy-looking insect with mottled-grey wings, and is sometimes very abundant in damp meadows. [Illustration: Fig. 136.--Hæmatopota Pluvialis (Mag.)] Many other species of _Tabanidæ_, popularly called "Breeze Flies," are plentiful in this country. _Family 18, Leptidæ._--These insects are mostly predatory, though many small species are parasitic on animals and other insects. The _larva_ of _Vermilio degeerii_ lives in sand, and feeds on such insects as fall in its way. Those of the genus _Leptis_ are parasitic on cockchafers and other large beetles. [Illustration: Fig. 137.--Vermilio Degeerii (Mag.)] [Illustration: Fig. 138.--Chrysopila Atrata (Mag.)] _Family 19, Asilidæ._--The _Asilidæ_ or Hawk Flies are a family of considerable extent, and include many very large and conspicuous insects. They feed on other insects, and are very courageous, sometimes attacking even dragon flies. One of the most common species is _Asilus crabroniformis_, which is common in the south of England. _Family 20, Midaidæ._--These are large insects resembling the _Asilidæ_ in their habits, and are nearly all tropical. A few species, however, inhabit the south of Europe.