10 BULLETIN" 922, U. S. DEPARTMENT OF AGRICULTURE. 
The cocoon (fig. 6) is spun in an oval 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 11 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wings are soon withdrawn beneath the elytra and within 24 hours 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. 
