44& 



THE STUDY OF INSECTS. 



emerges soon afterward, and lays its eggs in the newly- 

 started buds of the willow. 



There is a guest gall-gnat, Cecidomyia albovittata (C. al- 

 bo-vit-ta'ta), which breeds in large numbers between the 

 leaves composing the Pine-cone Willow-gall. The larvae of 

 this gnat do not seem to interfere in any way with the 

 development of their host, there being abundant food in the 

 gall both for the owner of the gall and for its numerous 

 guests. 



The Clover-leaf Midge, Cecidomyia trifolii{C. tri-fo'li-i). — 

 The leaflets of white clover are sometimes infested by white 



or orange-colored mag- 

 gots which fold the two 

 halves of the leaflet 

 together. From one to 

 twenty of these larvae 

 may be found in a single 

 leaflet. When f u 1 1- 

 grown the larvae make 

 cocoons, and undergo 

 their transformations 

 within the folded leaflet. In Figure 525 an infested leaf 

 containing cocoons is represented natural size, also a larva 

 and an adult gnat, greatly enlarged. 



The Clover-seed Midge, Cecidomyia leguminicola (C. le- 

 gu-mi-nic'o-la), is a much more serious pest of clover. This 

 infests both red and white clover. The larvae live in the 

 heads of the clover and destroy the immature seed. When 

 full-grown they drop to the ground, where they undergo 

 their transformations. In some parts of this country it is 

 impossible to raise clover-seed on account of this pest. 



The Hessian-fly, Cecidomyia destructor (C. de-struc'tor). — 

 This is perhaps the most serious pest infesting wheat in this 

 country. The larva lives at the base of a leaf between it 

 and the main stalk. There are two or three broods of this 

 insect in the course of the year. The larvae of the fall brood 



Fig. 523.— Cecidomyia trifolii. (From the Author's 

 Report lor 1879.) 



