December, '12] WEISS: LIXUS CONCAVUS 435 



remains and does practically all of its feeding until full grown. There 

 is one exception to this. Where the stem is thick and does not dry 

 out rapidly, some larvae eat a fairly large cavity in the base of the stem 

 before attacking the root. 



When the larvae are young it is possible to find two or three in dif- 

 ferent portions of a single stem. Later, however, one to a single plant 

 is the rule except where the root is large and supports several stems, 

 then it is possible to find as many as three occupying different parts 

 of the root. On seven different occasions I found larva? feeding upon 

 other larvae and I feel that this explains the fact that only one larva is 

 found in a plant containing numerous egg punctures. Inasmuch as 

 they are carnivorous, they undoubtedly devour eggs also. 



The first born larva evidently makes its way down the stem and 

 feeds on any eggs into which its channel may cut. The second hatch- 

 ing from a place above the first or from an egg which escaped the first 

 also makes its way down the stem and lives bnly until it reaches the 

 cavity in the root made by the first, when it is devoured, assuming 

 that the largest is always the victor. The second may also eat some 

 eggs on the way down. I imagine that this procedure is kept up until 

 only one remains. If the first larva goes some distance down in the 

 root, larvae hatching later may live longer if they cut a different chan- 

 nel, but in a small root supporting only one stem, the cavities are 

 bound to run together and not more than one is found in a root of this 

 kind. Undoubtedly some of the eggs which are laid late are crushed 

 by the drying and contraction of the stem, as by July 3 the tops of 

 many plants are dry and brown. From a large root supporting five 

 stems, containing fifty-eight egg punctures, only three larvae were 

 found and these were in different cavities. 



Of course some of these punctures may have been made for feeding 

 purposes, but as the beetles also feed on the edges of the leaves, it 

 seems somewhat unlikely that they would prefer the harder tissue of 

 the stems. 



From eight to nine weeks are required by the larvae to reach matur- 

 ity and in middle and south Jersey the majority are full grown by the 

 second week in August. Owing to the period over which oviposition 

 extends it is, of course, possible to find larvae only one third grown at 

 this date. As late as August 14, I have taken larvae one third grown, 

 full grown larvae, pupae and an immature beetle all on the same day. 

 In the field the first pupa? were collected August 1 and the first adults 

 on August 6. 



From the second to the fourth week in August, the majority in the 

 field were undergoing pupation and during the first week in September 

 many adults emerged. By September 11 practically all had emerged. 



