22 PRELIMINARY REPORT ON ALFALFA WEEVIL. 



larvae, as observed by him, were remarkably vigorous, very young 

 ones exhibiting great energy as travelers. Their mode of progression 

 is to reach forward and then, with a slight hump, to bring up the rear 

 part of the body. The head is at once thrust forward again. About 

 one move is made per second, and three propulsions will carry the body 

 forward 1 mm. When in doubt as to the direction to be taken, the 

 larva elevates the head and swings it from side to side until some 

 decision is reached, when the journey is resumed. The larvae are 

 positively phototropic. 



After working their way upward on the alfalfa stems the larvae 

 begin to feed close down between the opening buds on the unfolding 

 leaves. Their manner of feeding there, as observed by Mr. Ainslie, 

 was by scraping off the epidermis with a sort of burrowing motion, 

 leaving only the veins and fragments of uneaten tissue. This selec- 

 tion of the terminal buds may be in part due to the shelter offered 

 as well as to the more tender and succulent nature of the plant 

 growth. Large numbers of young larvae may, however, be found 

 feeding among the unfolding buds without being easily seen. This 

 feeding is further described by Mr. Titus * as follows : 



In feeding, the larvae bore holes into the buds [see fig. 4], working their way in 

 until they are often completely concealed inside the opening bud. The plant then 

 sends out other buds below this point, and usually other young larvae are present to 

 destroy these, so that at times the growing tips of the plants become so injured as to 

 give these tips the appearance of a gall. As many as 15 young larvae have been found 

 feeding in the terminal bud of one stalk. Sometimes, before they are fully developed, 

 in the second stage, they pass out onto the leaves, at first eating the upper epidermis 

 only. 



The larvae, after the usual habit of those of the genus to which it 

 belongs, either- cling around the edge of the leaf or feed in a curved 

 position. This continual eating off of the fresh growth keeps the 

 alfalfa so reduced that it does not produce a first crop. Seriously 

 affected fields are shown in Plate III, figure 1, and Plate IV, figures 

 1 and 2, while a field that has not suffered from such attack is shown 

 in Plate IV, figure 3. From these illustrations a good idea of the 

 damage done by the larvae to the first crop of alfalfa may be obtained. 



LARVAL PERIOD. 



From about 5 to 8 days after hatching from the egg the skin of 

 the larva splits and the old skin is pushed off, leaving the larva in a 

 new dress. This process is repeated after a period of from 12 to 20 

 days and again after about 12 to 30 days, as observed by Mr. Titus. 

 Mr. Ainslie in some instances got pupae in 18 to 20 days during May, 

 1910. These variations in time are probably largely due to tem- 

 perature, which again may be due in part to elevation. 



1 Bulletin 110, Utah Agr. Coll. Exp. Sta., pp. 40-42, September, 1910. 



