As far as their habits are known, they deposit their eggs in the nests of other insects, chiefly Hymenoptera, on the larvæ of which their own offspring feed.
The commonest British species is Chrysis ignita, which is a very variable insect, both as regards size and colouring.
Tribe III.—Phytophaga.
The insects belonging to the third tribe of the Hymenoptera are strictly vegetable feeders. There are only two families.
Family 25, Siricidæ.—This family includes the insects known as Tailed Wasps. It is not a very extensive family, and its species occur chiefly in Europe and North America, in both of which regions the typical genus Sirex is represented by large species.
The best-known European species which is common in some parts of Britain is the great Tailed Wasp (Sirex gigas), a very formidable-looking insect, of which the female often measures nearly an inch and a half in length.
Fig. 38.—Cimbex Luteus.
The general tint is black with the antennæ, the sides of the thorax and the legs and apex of the abdomen yellow. This insect lives in pine and fir woods, and the female deposits her eggs in the woody parts of the trees, into which she bores to a depth of over half an inch by means of her long ovipositor.