384 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



Life History. The beetles hibernate over winter in rubbish, 

 under logs, leaves or other vegetation, and emerge early in May, 

 They mate as soon as they have fed a little, and disappear by 

 the middle of June in New Jersey. But little is known of the 

 early stages of the insect and they have never been found or, 

 sweet-potato plants. The larvae have been found, however, 

 feeding on the roots of bindweed. The larva (Fig. 320) is a 

 slender, white grub, about one-eighth inch long, and feeds exter- 

 nally upon the smaller roots. The beetles appear again in August, 

 but do not as a rule feed on sweet potatoes, preferring bindweeds 

 and wild morning-glories, from which they disappear in late 

 September 



Control. By dipping the plants in arsenate of lead, 1 pound 

 to 10 gallons of water, as they are being set, they will be pro- 

 tected and any beetles feeding on them will be killed. The 

 plants should be allowed to dry slightly before being set. Dip- 

 ping the plants is much better than spraying them later, as it 

 is practically impossible to completely cover the plant by spray- 

 ing, as may be done in dipping, which is much quicker and less 

 expensive. Late-planted sweet potatoes are much less seriously 

 injured, as the beetles will seek out their wild food-plants and 

 become established upon them, so that late planting may be 

 resorted to when necessary or more convenient. Well grown, 

 stocky plants will better withstand injury, and liberal fertiliza- 

 tion will enable them to make a quick growth even if slightly 

 checked. 



Tortoise-beetles or Gold-bugs * 



Of all the insects affecting the sweet potato, the brilliant 

 little golden beetles which form one tribe (Cassidce) of the large 

 family of leaf -beetles, are the most common and are quite peculiar 

 to it. They are beautiful insects, some of the species appearing 

 like drops of molten gold, which has given them the name of 

 " gold-bugs," while the broad expansion of the thorax and wing- 

 covers gives them a fancied resemblance to a tortoise; hence the 

 name " tortoise-beetles." The species affecting the sweet potato 

 are classed in three different genera, but are sufficiently alike in 

 their general habits and life history to be treated together. 



* Family Chrysomelidce. 



