146 



APPLIED ENTOMOLOGY 



As soon as tunnels in the potato are formed, the tissues around them change 

 color and decay soon follows, so that an attack quickly ruins the value of the 

 crop. 



Control. — Sweet potatoes found infested ever so slightly should immediately 

 be destroyed, either by feeding to stock or in some other way. If any area 

 becomes infested no sweet potatoes should be planted there for several years, 

 and as it is probable that the insect can also breed in the wild morning glory, all 

 plants of this species should also be destroyed as far as possible within the area. 

 Spraying the plants with arsenate of lead or other stomach poison, applied as soon 

 as the beetles appear has recently given encouraging results. Following sprays 

 at about ten-day intervals may be given if necessary. 



Family Ipidae (formerly Scolytidse) (Bark beetles or Engraver beetles). 

 The members of this family are borers and nearly all attack the inner 

 bark or wood of trees. They are small insects, from one twenty-fifth 

 to two-fifths of an inch long, 

 brownish or blackish in color, 

 and usually with cylindrical 

 bodies (Fig. 142). In habits 

 they form two chief groups. In 

 the so-called Ambrosia-beetles 

 the tunnels extend through the 

 wood and the young develop 

 there: in the True Bark-beetles 

 the tunnels are formed either in 

 the inner bark or between this 

 and the wood. The adult in 



Fig. 142. i'lG- 143. 



Fig. 142. — Adult Bark Beetles, greatly enlarged. {Modified From Felt: ISf. Y. State 

 Mus. Mem. 8.) 



Fig. 143. — Work of Bark Beetles on inside of bark, slightly reduced. {Original.) 



either case cuts a tunnel slightly larger than itself in to the inner bark 

 or through this, but the Ambrosia-beetles continue it on, into the 

 wood. The Bark-beetles having arrived at the desired depth, turn and 

 excavate one or more channels between the bark and the wood, which 

 become the egg tunnels. Along the sides of these the eggs are deposited, 

 either singly in little hollows, several together in larger excavations, or 



