228 INJURIOUS AND USEFUL INSECTS 



up the inside of the growing haulm, and when full-fed, 

 descends to near the ground, where it girdles the haulm, biting 

 it nearly through, so as to provide for its own escape as a fly. 

 Then it descends lower still, makes a cocoon, and winters 

 below the surface, changing to a pupa in May, and appearing 

 as a fly when the corn has gained a fair height. The girdled 

 haulms are greatly impoverished and easily snap across in a 

 wind. Though the corn-saw-fly is a serious pest on the Con- 

 tinent, and common in Britain, it rarely does great damage 

 here. 



Sub-order II. — Parasitica 



Family Cynipidae (gall-flies). Small, sometimes very small 

 flies, which as larvae inhabit galls or dwell parasitically in the 

 bodies of other insects. A variety of galls are formed on the 

 oak, and one is common on rose-trees. Cynips tinctoria forms 

 galls on Quercus infectoria, which are known in commerce as 

 Aleppo, Turkey, or Levant galls, and are largely used in tan- 

 ning, dyeing, and ink-making. 



Family Proctotrypidae. Ichneumon like parasites, many of 

 them egg-parasites. 



Family Chalcididse. Gall-makers or parasites. To this 

 family belong the very curious fig-insects \Blastophagd) which 

 are essential to the pollination of the cultivated fig.* The 

 females are winged and the males wingless, a singular excep- 

 tion to what is found in other insects (see pp. 78-81). 



Family Ichneumonidse (the true ichneumon-flies. See 

 Lesson 22). 



Family Braconidae. Ichneumon-like parasites. It is to be 

 remarked that the habit of laying eggs in the bodies of other 

 insects seems to have been acquired independently by distinct 

 families of Hymenoptera ; also that there is no sharp distinction 

 between gall-makers and insect-parasites ; some families include 

 both. 



Sub-order III. — Aculeata 



Family Chrysididae (ruby-wasps). These are small, bright- 

 coloured, and very active insects, which usually lay their eggs 

 in the cells of other Hymenoptera. 



* See a very full and interesting report on Smyrna fig-culture in the 

 United States, by Dr L. O. Howard (Year-book of U.S. Dept. of 

 Agriculture, 1901). 



