The species of _Sapyga_ occur in Europe and North America. They are supposed to be parasitic in the nests of bees, but the females of the common European species (_Sapyga pacca_) have been observed carrying small caterpillars, from which Mr. Smith (the great authority on Hymenoptera) justly infers that they are parasitic only to the extent of usurping the burrows made in sandbanks and dead wood by more industrious insects, their own structure not adapting them for the labour of digging. _Family 14, Scoliidæ._--Although this family is abundant in warm climates, we have only two small species belonging to the genus _Tiphia_ in Britain. They are black, with more or less reddish legs, and measure from a quarter to half an inch in length. In south Europe we meet with several large and handsome species, one of which, _Scolia hortorum_, is black with two yellow bands on the abdomen. [Illustration: Fig. 23.--Scolia Hortorum.] _Family 15, Thymidæ._--The insects of this family are almost exclusively confined to Australia and South America, where they are very numerous. They are generally of a black colour, with more or less extended yellow markings. They are very stout insects; in fact, their bloated bodies give them very little resemblance to any other insects, except perhaps to the Oil Beetles. Very little has hitherto been ascertained respecting their habits, but they are believed to be parasitic. [Illustration: Fig. 24.--Mutilla Maura (Male).] _Family 16, Mutillidæ._--This family includes a large number of species, probably 1,500, but from the differences presented by the males and females, entomologists have found it difficult to arrive at any certainty upon this point. The species are spread over all the earth, but are particularly abundant in warm climates, where also, as usual, they attain the largest size and the most beautiful colouring. One of the best-known species in our own country is _Mutilla europæa_, which is about half an inch long, of a black colour, hairy, with the thorax entirely red in the wingless females. [Illustration: Fig. 25.--Mutilla Maura (Female).] This insect frequents the nests of Humble Bees, and its _larvæ_ appear to be parasitic upon the _larvæ_ of the bees. _Section 4.--Heterogyna._ _Family 17, Formicidæ._--To this family belongs the numerous species of ants, which are social insects, organised after the fashion of the bees and social wasps. The number of species described is probably considerably over a thousand, but the total number must be very much greater if Mr. Bates is correct in his estimate that not less than 400 species inhabit the valley of the Amazon. [Illustration: Fig. 26.--Formica Lignipeda (Male). (Mag.)] The habits of the ants are most interesting, and one of our greatest living naturalists, Sir John Lubbock, has devoted much of his time in elucidating their economy.