INSECTS INJURIOUS TO THE SWEET POTATO 437 



even from the same lot of eggs. The expansion of the margins 

 of the wing-covers and prothorax found in the other tortoise- 

 beetles is almost lacking. The eggs are laid in a bunch, each 

 supported by a long stalk or pedicle. When the larvae hatch 

 they huddle together on the leaves and very rapidly defoliate a 

 plant. When full grown a larva is about one-half inch long with 

 the faeci-fork half as long again, slightly convex above, of a dirty 

 yellowish color marked with numerous dark-brown tubercles 

 and prominent lateral spines as shown in Fig. 313. The larva 

 usually stands with the caudal segments elevated and the faeci- 

 fork slanting backward. The pupa is of a yellowish color ; 

 marked with dark brown, which becomes almost black. The 

 ground color of the pupa is almost concealed by a bluish bloom 

 or waxy excretion resembling mold. 



Control. From the similarity of their life history and habits 

 all of these species may be treated at once. As the beetles do the 

 most injury just after the plants are set, they should be dipped 

 in arsenate of lead when setting, as advised for the flea-beetle. 

 If this has not been done or if the beetles are injurious in the 

 forcing bed, the plants should be thoroughly sprayed with 

 arsenate of lead, 3 pounds per barrel, or Paris green, ^ pound per 

 barrel with pound of freshly slaked lime. 



Saw-flies * 



In 1886, Dr. C. V. Riley described the injury and various 

 stages of a saw-fly,f the larvae of which had practically ruined a 

 crop of sweet potatoes at Ocean Springs, Miss. The pest was 

 somewhat injurious for the next two years, but since then has 

 not been specially injurious, though adult flies have been noticed 

 on sweet-potato and morning-glory vines in Nebraska. Doubt- 

 less its control is due to the effective work of parasites which 

 were reared by Dr. Riley from the larvae, and which probably 

 prevent the undue increase of the species. 



* Family Tenthredinidoe. 

 t Schizocerus ebenus Norton. 



