542 



AN INTRODUCTION TO ENTOMOLOGY 



all of these are known as ambrosia-beetles. The galleries of ambrosia- 

 beetles are usually blackened by the fungus. See further account of 

 the ambrosia -beetles in the discussion of the next family. 



Family SCOLYTIDiE 



The Engraver-Beetles and the Ambrosia-Beetles 



Fig. 666. — Phthoro- 

 phlceus liminaris. 



The members of the family Scolytidse are mostly of cylindrical 

 form (Fig. 666) and of small or moderate size; some species measure 

 only I mm. in length, but 

 others are much larger, at- 

 taining a length of 6 mm. 

 or more. They are usually 

 brown, sometimes black, and 

 with many the hind end of 

 the body is very blunt, as 

 if cut off. The antennae are 

 elbowed or bent in the mid- 

 dle, and are clubbed at the 

 tip; the tibiae are usually 

 serrate; and the first seg- 

 ment of the anterior tarsi is 

 shorter than the second, 

 third, and fourth together. 



A few members of this family infest herba- 

 ceous plants ; our most important one of these is 

 the following. 



The clover-root borer, Hylastinus ohscurus. 

 — This pest was introduced from Europe and 

 has become the most serious enemy of clover, 

 especially red clover and mammoth clover, in 

 New York State and in other sections of the 

 North. It bores in the roots of plants beginning 

 their second year of growth and destroys them 

 (Fig. 667) . Where it is common it is practically 

 impossible to keep fields in clover longer than 

 the second stmuner after seeding. In these 

 regions it is the common practice to seed with 

 clover and timothy mixed; after the clover 

 disappears the field becomes a timothy meadow. 

 No practical method of control of this pest has 

 been found. 



Fig. 667.— Work of clo- Most scolytid beetles infest woody plants; 

 ver-root borer. (After among them are some of the most destructive 

 Webster.) enemies of forest-trees, and a few attack fruit- 



trees. As a rule they are more liable to attack sickly trees, but their 

 injuries are not confined to these. 



