316 MANUAL OF VEGETABLE-GARDEN INSECTS 



for seed. The full-grown larva is about i inch in length with 

 a brown head and yellowish brown thoracic shield. The 

 larvae are sometimes found with the front part of the body 

 inserted into the tuber, from which the remainder of the body 

 projects. The tissue surrounding the larva in the tuber be- 

 comes hardened and turns blackish. Under some conditions 

 the presence of the grub causes an abnormal growth on the 

 surface of the tuber about 4 to i inch in diameter, low% convex 

 and scurfy at the top. Tubers so affected are called pimply 

 potatoes and their market value is considerably lessened. 

 The larvse have also been found feeding on the roots of tomato, 

 eggplant and the common nightshade. When mature they 

 transform within small earthen cells to whitish pupae about 

 tV inch in length and in six to eight days transformation to 

 the adult takes place. On Long Island the beetles of the new 

 brood begin to appear in early July and in INIaine about the 

 middle of the month. Some of the beetles continue feeding 

 until cold w^eather, when they go into hibernation. Nearly 

 all the females do not oviposit until the following spring, but 

 it is quite probable that a few of them soon after emerging 

 lay eggs from wdiich there is produced a small second brood 

 of beetles in late summer or early fall. This second brood 

 goes into hibernation with those of the preceding generation. 



The beetles that have hibernated feed ravenously until the 

 eggs have been laid and then gradually decrease in numbers. 

 Thus, during late June and early July, they are much less abun- 

 dant in the field than earlier in the season or a little later when 

 the beetles of the new brood begin to appear. The dying off 

 of these over-wintered beetles has often misled growers into 

 thinking that they had been killed by spraying. 



While the larvae are sometimes injurious to the tubers, this 

 type of injury is not common. The most serious injury is to 

 the foliage. Not only is the leaf surface greatly reduced by 

 the feeding of the beetles and the consequent killing of the 



