544 



AN INTRODUCTION TO ENTOMOLOGY 



The fruit-tree bark-beetle, Scolytus rugiilosus. — This species in- 

 fests apple, quince, plum, peach, and other stone-fruits. It is some- 

 times called the shot-hole borer by fruit-growers on account of the 

 small entrance holes of its burrows. The adult beetle measures from 

 2 mm. to 2.5 mm. in length, and is dark brown or nearly black. It 

 infests chiefly sickly trees. 



The peach-tree bark -beetle, Phthorophlceus limindris. — This spe- 

 cies resembles the preceding in size and habits, except that its injuries 

 are confined chiefly to peach and cherrv^ It can be distinguished from 

 the fruit-tree bark-beetle by the fact that the club of the antennse is 

 lamellate, an unusual feature in this family (Fig. 666). 



The Ambrosia-Beetles or Timber-Beetles 



Certain members of the family Scolytidas differ in habits from the 

 engraver-beetles or bark-beetles in a remarkable manner; these are 

 those known as ambrosia-beetles or timber-beetles. Thev are termed 



Fig. 669. — Gallery of Monarthnim malt in maple. (From Hubbard.) 



ambrosia-beetles because they cultivate fungi, commonly called am- 

 brosia, upon which they feed; and timber-beetles, because they 

 burrow in the solid wood. 



The galleries of the ambrosia-beetles can be distinguished from 

 those of other wood-boring insects by the fact that in all of their 

 ramifications they are of uniform size and free from wood-dust and 

 other refuse, and their walls are stained black or brown by the fungus 

 that is grown upon them. 



The galleries of different species differ in form; but usually there 

 is a main gallery, which extends deeply into the solid wood and is 

 often branched; and extending from the sides of the main gallery 

 there are short chambers, termed cradles, in each of which an egg is 

 laid and a larva reared (Fig. 669). In some species, the female de- 

 posits her eggs loosely in the galleries, and the young and old live 

 together in the same quarters. 



