166 KOOLOGT. 



a luxuriant growth of vegetable tissue takes place 

 later on, of varying extent, and even forming a 

 regular gall. The species of gall gnat are usually 

 brightly coloured, often red or yellow ; these colours 

 are lost, however, in dried specimens. The larvse 

 are spindle-shaped, yellowish white, yellow, or red ; 

 they become pupae either in the soil or within the 

 part of the plant which they inhabit. Several species 

 are destructive to fruit-tree culture or forestry; I 

 mention here only the most destructive kinds which 

 attack cultivated plants. 



The Hessian Fly (Cecidomyia destructor). 



Female about one-eighth of an inch long, male some- 

 what smaller. The former velvety black, with black 

 hairs, red belly, and red markings ; wings greyish ; 

 antennae one-third the length of the body. Male 

 black, with reddish-yellow hairs, dirty red belly, and 

 red markings. The name " Hessian flies " was given 

 in North America, during last century, because it was 

 believed they were introduced from Germany, in 1778, 

 by Hessian soldiers, in their straw. It is still very 

 destructive in North America, also in Germany, 

 Russia, England, and Scotland. Habits : During 

 April or May, on warm still evenings, the female lays 

 her eighty or ninety eggs, singly or in pairs, on the 

 lowest leaves of the still very short haulms of rye, 

 wheat, and barley. Eight days, on an average, after 

 this the maggots, which are at first oblong and 

 spotted with reddish yellow, are hatched, and glide 

 down into the leaf-sheath, where they begin to suck 

 the haulm. They gradually alter their shape, be- 

 coming ovoid, and transparent with the exception 

 of the large yellowish- white, quite opaque fat body. 

 They soon become pupse (Fig. Ill), which look like 

 grains of linseed, and are found in summer on the 

 haulms of the ripe grain. The presence of the 

 constantly sucking larvae causes great and injurious 



