THE COWPEA CTJRCULIO. 141 



His information regarding C. seneus was probably derived from the 

 results of Doctor Chittenden's cage experiments, carried on in Wash- 

 ington, D. C. In no case, out of the several hundred beetles reared 

 by the writer, did one pupate before leaving the pea and the pod 

 in which the larva developed. 



When full grown, the larva cuts a hole to the outside of the pea 

 and then through the pod and drops to the ground. The opening in 

 the pod is frequently at some distance from the injured pea. It is 

 quite regular, circular in outline, about 2 mm. in diameter, and the 

 disk which is cut out often remains hinged at one side. After drop- 

 ping to the ground the larva immediately begins to burrow into the 

 earth. In well-settled, damp sand the larva can disappear in about 

 one minute. In the fall of 1908 several big jars of cowpea pods were 

 kept under observation. The larvae emerging from the pods con- 

 tained therein were each day transferred to small jars containing 

 damp sand. Several hundred larvae were thus obtained and prac- 

 tically every one of them disappeared into the sand as soon as the 

 opportunity was offered. The larva penetrates the ground to a depth 

 of from 1 to 4 inches, depending on the compactness of the latter. 

 Two jars were prepared with equal depths (about 2 inches) of damp 

 sand, that in the first being settled as compactly as possible* and that 

 in the other put in loosely. Eighteen larvae were put into the first 

 and of this number only 3, or 17 per cent, reached the bottom, while, 

 of 33 put into the loose sand, 10, or 30 per cent, reached the bottom. 

 The larger and more active grubs burrow deeper and more rapidly. 

 After reaching the necessary depth, the larva by the motion of its 

 body proceeds to form an oval cavity somewhat larger than itself. 

 It spins no cocoon whatever. 



The exact time of hatching of several larvae was determined, and 

 these were transferred to fresh peas. The young larvae do not seem 

 to be able at first to penetrate the smooth coat of the pea, but when 

 an opening is made for them they accept it at once. The length of the 

 larval period spent in the pea was accurately determined for 12 larvae. 

 In most cases the larva had to be transferred to fresh food one or 

 more times because of the decay of the mutilated pea. These 12 

 larvae fed as follows: Four fed for 7 days; 2 fed for 8 days; 1 fed for 

 9 days; 4 fed for 10 days; and 1 fed for 12 days. This gave an 

 average feeding period of 8} days for the lot. The larval period in 

 the pea can safely be said to vary from 7 to 14 days, depending on 

 the temperature and the food supply. 



After entering the ground the larvae do not pupate at once, but 

 remain quiescent for several days in the earthen cells. In 11 jars in 

 which the length of the period was recorded all the visible larvae had 

 pupated in 5 days, in 8 jars it required 6 days, and in 2 jars 7 days, 

 giving 6 days as the average and from 2 to 8 as the probable extremes. 



