﻿20 BULLETIN" 1357, U. S. DEPARTMENT OF AGEICULTUEE 



moving backward through the opening, after which it crawled inside 

 and began to chew and swallow small portions of the broken shell, 

 consuming about one-fourth of it. About an hour later it turned 

 around and chewed at the other end. After 70 minutes the head was 

 still rather transparent but had become brownish. 



When observed at 10.15 a. m., specimen B was curled up in the 

 shell, flexed dorsally at about the division of the thorax and ab- 

 domen, and seemed to be pushing upward on the shell. No ruptures 

 in the shell were visible at this time. The larva then straightened 

 out and twisted itself around so that its mouth reached the place 

 where the back had been pressing against the shell, where it had 

 chewed an opening by 10.55 a. m. At 11.45 a. m. it again returned to 

 its first position and was pressing with its back against the break in 

 the shell, enlarging the opening. A wavelike motion, extending from 

 the tip of the abdomen forward toward the head, accompanied the 

 pushing and helped break open the shell. Following this the little 

 larva straightened its head and thorax, keeping the abdomen in the 

 same position as when pushing. The opening was apparently not 



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16. 8. — Strawt 



lerry rootworm. 





Lateral view of larva, enlarged 



large enough for the head to get out. At noon the larva, by curling 

 the end of its abdomen slightly forward, shoved itself backward until 

 its head could be thrust out through the opening made. At this time 

 there was no differentiation in the color of the head and the body. 



LARVA STAGES 



The full-grown larvae or grubs (fig. 8) are from 4 to 5 millimeters long and 

 1.1 to 1.4 millimeters wide. They are entirely white except for the head and 

 the dorsal surface of the prothorax, which are pale yellowish brown. The 

 prothoraeic segment, which is firmer in structure and bears only one fold, 

 is leathery and smooth above and a little longer than the other segments. The 

 remaining segments are each marked with three transverse dorsal folds, \vhich 

 terminate on the sides in large, low elevations, pointed ovate in form (the 

 pointed ends being upward), one to each segment of the body excepting the 

 head, prothorax, and anal segment. 



There are nine spiracles on each side of the body, the first larger than the 

 others and located between the prothoraeic and mesothoracic segments, whereas 

 the others are placed on the abdominal segments, except the last. They are at 

 the lower ends of the ovate elevations mentioned above. Below the row of 

 spiracles there is a row of prominent tubercles, one to each segment, forming a 

 longitudinal groove between this row and the elevations above the spiracles. 

 On each ovate elevation there is just above the spiracle a small mound from the 

 center of which arises a seta. A similar seta arises from each tubercle of the 

 first row. Below this row of tubercles is a longitudinal fold on each segment, 



2 The description of the larva is based on that given by Forbes i^lZ, pp. 151-152), with 

 some additions and modifications. 



