DIPTERA. NEMOCERA. 345 



plants, and some on decaying wood and even in the 

 woody galls formed by other insects. 



As was observed above concerning the Lepidoptera, 

 so here it may be repeated of Diptera that a study of 

 the order, and especially of this family, will inform the 

 young naturalist of the history of many of the excres- 

 cences, monstrosities, and, in some cases, decorations, 

 which he cannot fail to observe in any country walk. 

 The larvae of some of the Cecidomyzidae live in the leaf- 

 buds at the tip of the branches of the dwarf willows 

 which fringe the pools and river-sides in every part of 

 the country, and there form rosette-like galls. 



The wart-like galls common on the meadow-sweet 

 (Spiraea) ; the uneven swellings on the stalks and leaves 

 of the stinging-nettle ; the little furry, purses on the 

 ground ivy ; the woody, shapeless excrescences on the 

 raspberry plants ; the slender upright growth on beech 

 leaves ; the blisters on bedstraw, yellow nettle, and 

 others ; the knots within the very blossoms of many 

 flowers ; all these, and a great many more, are the work 

 of little creatures in this numerous family. 



A few of them have been found in woody galls of 

 Hymenopterous insects ; some others are Aphis-eaters. 



Besides these, some of the larvae live within the stalks 

 of groundsel and other allied plants ; others live in 

 rolled leaves, and one, the Cecidomyia tritici, is a scourge 

 to the farmers, inhabiting the ears of corn. It will give 

 some idea of the destruction of which these insects are 

 capable, to relate that forty-one of their maggots have 

 been counted in the husk of a single grain of wheat ! 

 The Hessian Fly of America belongs to this family. 



Some of the larvae in Oecidomyzidae spin silken cocoons. 



3. Bibionidce. This is a small familv of rather stouter 



