10 BULLETIN 922, XT. S. DEPARTMENT OF AGRICULTURE. 



The cocoon (fig. 6) is spun in an ovai cell made by the larva in the 

 soil just beneath the surface or among the stems and rubbish at the 

 base of the clover plant. This cell is formed by the larva turning 

 around and around with its body in the characteristic curved posi- 

 tion and is smoothed with its head. The spinning is done by the 

 mouth but the bulk of the spinning material is drawn from the anus 

 and every few minutes during the construction of the cocoon the 

 larva reaches back to the anus for a fresh supply. Knab (4) shows 

 by his dissections of these larvae that there is an enormous develop- 

 ment of the malpighian tubes and reasonably supposes that the 

 bulk of the spinning material primarily arises in these tubes and is 

 drawn from the anus by the larva. He further observes that the 

 necessarily smaller amount of silk produced by the silk glands which 

 open into the mouth may be used in waterproofing the other materials, 

 for he has noticed' the larva passing its mouth along the threads 

 after they have been drawn out and put in place. 



The cocoon is spun in from 1 to 2 days and the larva pupates 

 within four days after the cocoon is completed. In one instance at 

 La Fayette, during excessively hot weather, a larva pupated within 

 a day after completing the cocoon, and in another instance under 

 adverse conditions this prepupal period extended over 10 days. The 

 newly formed pupa is pale green but later changes to yellow and 

 finally to a brownish color. 



The beetle issues 5 to 16 days after pupation, the average pupal 

 period, according to our observations, being 1 1 days. The adult is 

 at first soft and pale green, the wings protruding beyond the elytra, 

 the pupal and larval skins remaining as a small shriveled pellet at 

 an end of the cocoon. The elytra gradually become silver, iri- 

 descent, and pale green through which the maculations are faintly 

 visible, the ventral surface of the abdomen is pale green, the lower 

 part of the head reddish brown, the prothorax tan colored. The 

 wings are soon withdrawn beneath the elytra and within 24 hours 

 the insect has become mature, after which the beetle issues by eating 

 an irregular hole in the cocoon. The first beetles issuing at La 

 Fayette in 1916 emerged on May 26 and the last June 26, although 

 other observers in the same latitude give the period of greatest 

 emergence as the last week in June, the period of emergence extend- 

 ing from May 9 to July 15. 



After emergence the beetles feed during the night and conceal 

 themselves during the day under rubbish or in cracks in the ground. 

 They feed steadily for about two weeks, after which they become 

 semidormant and remain inactive until about the first of Septem- 

 ber, whereupon they become sexually active. 



