144 



APPLIED ENTOMOLOGY 



black after a time. It winters as the adult close to the ground or in crevices 

 there, and in some cases under rubbish, and in severe winters many are killed by 

 the cold. As soon as warm days come the weevils become active and lay eggs 

 in the dry alfalfa stems, before the regular laying season, and the larva? from these 

 eggs attack the young plants, often causing serious injury. The weevils also feed 

 on the plants quite freely at this season. After a few weeks the true egg-laying 

 period begins and the adults now puncture the living alfalfa stems and lay their 

 eggs in them, this process usually being finished by the tenth of June, though a 

 few eggs are laid much later. The eggs hatch in about ten days and the larva? 

 (Fig. 139) consume the alfalfa leaves, those from the ones laid early beginning to 



Fig. 138. Fig. 139. Fig. 140. 



Fig. 138. — Adult Alfalfa Weevil {Phytonomus posticus GyU.) much enlarged. (From 

 U. S. D. A. Bur. Ent. Bull. 112.) 



Fig. 139. — Side view of larva of Alfalfa Weevil, greatly enlarged. {From U. S. D. A. 

 Bur. Ent. Bull. 112. 



Fig. 140. — Cocoon of the Alfalfa Weevil, greatly enlarged. {From U. S. D. A. 

 Bur. Ent. Bull. 112.) 



feed in May, while later individuals are feeding until into July or even August, 

 with some stragglers later. The larval period varies greatly, but an average 

 length of time in this stage would be perhaps a month. When full-grown the 

 larva goes to some protected place such as a dry, curled leaf or dead vegetation 

 near the ground and spins a cocoon (Fig. 140) in the form of a loose network, in 

 which it pupates. This stage lasts about 10 days before the appearance of the 

 beetle. In late summer these beetles begin to look for winter shelter and in this 

 search may spread some distance. In spring a somewhat similar flight in search 

 of food, also increases their spread. This insect feeds on various species of clover 

 in addition to alfalfa, and as it seems to be persistently spreading, it must be 

 considered a menace to nearly all parts of the country. 



Control. — The most serious injury to the crop is that caused by the spring 

 feeding before the first cutting, and this also delays the production of the second 

 crop. Any treatment of the field, such as disking it with a harrow, which will 

 hasten growth at that time will be a gain. Spraying these fields with arsenate of 

 lead, 1 lb. of the paste in 50 gal. of water, appears to reach many of the insects 

 and be quite effective. Pasturing during the spring months, dividing the fields 

 so that each piece may be grazed close about once every 2 weeks, and continuing 

 this until most of the eggs of the weevil have been laid, has also given good 

 results, as has cutting and feeding the crop before the eggs hatch. Spraying 



