INSECTS INJURIOUS TO CLOVER 



215 



The adult is a small wasp-like fly one-twelfth to one-sixteenth 

 inch long, black in color, and with four wings, the hind-wings very 

 small and the fore-wings with but a single vein. It belongs to a 

 family almost all of which are parasitic on other insects, and for 

 many years it was thought to be a parasite of the clover-seed 

 midge, until its true role was discovered. In recent years exam- 

 inations of ripening heads from all parts of the country show that 

 it is probably distributed wherever clover is grown and that from 

 20 to 80 per cent of the seed is often destroyed. Both red and 

 crimson clovers are attacked, while alfalfa seed is not so badly 

 injured. 



f 



FIG. 154. The clover-seed chalcis: a, egg highly magnified; b, larva 

 and head more enlarged; c, pupa much enlarged. (After Webster, 

 U. S. Dept. Agr.) 



Life History. The winter is passed by the fully grown larvae 

 in seed on the ground. The adults emerge in the spring, the maxi- 

 mum appearing about June 10th in central Illinois, according to 

 Dr. Folsom, to whom we are indebted for the most careful study 

 of the pest. The females deposit their eggs in the soft seed, just 

 as the floret is withering, being unable to penetrate the seed after 

 it has hardened. The egg is whitish, about T J^ inch long, and 

 with a peculiar tail-like appendage (Fig. 154). The maggot-like 

 larva feeds upon the seed, gradually hollowing it out, and when full 

 grown is about one-twelfth inch long, stout and footless, with a 

 small head. The pupal stage is passed within the seed and a sec- 

 ond generation of adults emerges about the middle of August. 



