HOW TO KNOW THE IMMATURE INSECTS 

 137b. Head capsule narrowing posteriorly and with curved sides... 138 



138a. Abdominal hypopleuron subdivided into at least 2 lobes. 



(See Fig. 352) 141 



138b. Abdominal hypopleuron not subdivided 139 



139a. Abdominal segments with no more than 2 transverse dorsal 

 plicae. (See Fig. 350) 140 



139b. Abdominal segments with 3 or 4 transverse dorsal plicae. 



Fig. 348 and 349. . .FamiKes CURCULIONIDAE and SCOLYTIDAE 



These two families are not separable by 

 larval characters. The Curculionidae is prob- 

 ably the largest family of insects, it includes 

 about 40,000 known species. 



Fig. 348. Tychius piel- 

 rostris (Fab.) (Cucur- 

 lionidae) 



The larvae feed on roots, fruits, leaves, seeds and 

 also live as borers and leaf miners. No truly aquatic 

 forms are known although the larvae of many species 

 live in the roots of plants growing in bogs and 

 marshes. The female usually uses her snout to make 

 a hole in the plant tissue into which the eggs are 

 thrust. 



The Scolytidae is also a large family comprising 



about 2.000 known species. The adults are called 



'rRQtz.)"^"sco' ba^k beetles or engraver beetles. Their larvae live 



iytidae( in galleries in dead or healthy shrubs and trees. They 



attack all parts of the plants. In the United States alone the annual 



losses in destruction of timber has been estimated at about $100,000,000. 



Fig. 349. Shot- 

 hole borer, Sco- 



126 



