June, '16] FINK: DIABROTICA INJURY TO PEANUTS 367 



known, at times, to seriously injure truck and other crops by feeding 

 on the roots. Particularly is this the case with a growing crop like 

 corn, that occupies the land for a comparatively long time. 



Since 1908,^ and especially for the past three years, peanuts, which 

 were hitherto considered to be free from insect attack, were observed 

 to be injured by larva boring into the pods just as they were beginning 

 to form, and afterwards almost entirely destroying the contents by 

 feeding on the interior tissues. During the years 1913 and 1914, owing 

 to the few larvse then actually found in the pods, no attempt was made 

 to rear the adult. In the summer of 1915, however, the injury to 

 peanut pods was observed to be extensive, and larvse comparatively 

 abundant with the result that the reared adults were determined as 

 Diabrotica 12-punctata 01. 



Nature and Extent of Injury 



At the Virginia Truck Crop Experiment Station, Norfolk, Va., two 

 plats — each about a third of an acre in size — are used experimentally 

 for the growing of peanuts. Plat 1 is used exclusively for peanuts. 

 In plat 2, peanuts are used in rotation with corn and potatoes, once 

 in three years. At intervals during the months of August and Sep- 

 tember, 1915, peanut plants were dug from both plats, and the pods 

 were carefully examined to determine the extent and nature of the 

 injury. Observations made at the time indicated that the younger 

 and softer pods were usually the most seriously injured. The num- 

 ber of holes found in a pod varied from one to three or more, but 

 rarely was more than one larva found in a single pod. The larvae 

 attack the pods at various places appearing, however, to favor the 

 free end. After gaining entrance to the interior, the larva feeds on 

 the contents. In more matured pods their work becomes more de- 

 fined by tunnelling through the kernels. Injured pods when cut 

 longitudinally clearly show this condition (see PL 27, Fig. 2). 



In many instances young larvae gain entrance to pods in which the 

 rate of growth is proportionally greater than the growth of the larvae. 

 As the food contents soon become too hard, the larvae invariably 

 leave such pods to enter others. Matured peanut pods, as a rule, 

 are seldom observed injured, although the exterior of such pods 



1 Observations were conducted on this larva on peanuts that year bj' Messrs. 

 C. H. Popenoe and F. H. Chittenden, and the following year by Mr. E. G. Smyth. 



EXPVANATION OF PlATE 27 



Fig. 1. Peanut pod showing entrance and exit holes made by the larvae of the 

 twelve-spotted cucumber beetle (Diabrotica 12-punctata). 



Fig. 2. Peanut pods cut longitudinally to show the work of the larvae of the 

 twelve-spotted cucumber beetle {Diabrotica 12-punctala.) 



