236 MANUAL OF VEGETABLE-GARDEN INSECTS 



of beetles is produced in July. The new beetles feed for a 

 short time and then go into hibernation. There is only one 

 generation a year, at least in the northern states. 



The striped tortoise beetle, Cassida bivittata Say 



This is the commonest and most injurious species attacking 

 sweet potatoes in New Jersey and is widely distributed through- 

 out the regions in which this crop is grown in the eastern United 

 States. The beetle (Fig. 143) is about ^ inch in length ; the 

 prothorax is reddish with the margin yellowish; 

 v^ ^s"> ^^^^ wing-covers are dull yellow marked with five 

 -i&.\ longitudinal black stripes ; the underside of the 

 body and the legs are dark brown or black. The 

 beetles appear in the field in early spring and 

 feed for a time on wild morning-glory and attack 

 the sweet potato plants as soon as they are set 

 Fig 143 —The out in the field. The eggs are glued to the under- 

 striped tor- side of the leaves singly and hatch in a few days. 

 ( x^ 5) ^^^^^^^ '^^^ larva is yellowish white with a grayish longi- 

 tudinal line along the middle of the back. This 

 larva differs from the other species infesting the sweet potato in 

 not mixing excrement with the cast skins carried on the anal fork. 

 This appendage is not carried close to the back but is usually 

 elevated at an angle of about 45 degrees. When full-grown, 

 the larva attaches itself to the leaf by the tip of its body and, 

 after resting for two days, the larval skin splits along the back 

 and is pushed back towards the hind end of the body where it 

 is retained surrounding the point of attachment. When fully 

 colored, the pupa is dull brownish and may be distinguished 

 from the other species by the elongate whitish mass of cast 

 skins on the anal fork which still adheres to the insect. The 

 beetles emerge in July and after feeding a short time on the 

 leaves of sweet potato and wild morning-glory go into hiber- 

 nation early. 



