V KHYNCHOPHORA SCOLYTIDAE — BRENTHIDAE 295 



teristic in form and direction, so that the -work of particular 

 Scolytids can be recognised by the initiated. 



The Platypides bore into the wood of trees and stumps ; they 

 are chiefly exotic, and little is known about them. They are 

 the most aberrant of all Ehynchophora, the head being remarkably 

 short, flat in front, with the mouth placed on the under surface 

 of the head, there being no trace of a rostrum : the tarsi are 

 elongate and slender, the third joint not being at all lobed, while 

 the true fourth joint is A'isible. Hence they have not the 

 appearance of Ehynchophora. Some authorities treat the 

 Platypides as a distinct family. 



Some of the members of the group Tomicides also bore into 

 the wood. Eecent observations have shown that there is an 

 important feature in the economy of certain of these wood- 

 borers, inasmuch as they live gregariously in the burrow, and 

 feed on peculiar fungi that develop there, and are called ambrosia. 

 According to Hubbard,^ some species cultivate these fungi, 

 making elaborate preparations to start their growth. The fungi, 

 however, sometimes increase to such an extent as to seal up the 

 burrows, and kill the Insects by suffocation. 



Scolytidae sometimes multiply to an enormous extent, attack- 

 ing and destroying the trees in wooded regions. Much dis- 

 cussion has taken place as to whether or not they are really 

 injiirious. It is contended by one set of partisans that they 

 attack only timber that is in an unhealthy, dying, or dead con- 

 dition. It may be admitted that this is usually the case ; yet 

 when they occur in enormous numbers they may attack timber 

 that is in a sort of neutral state of health, and so diminish its 

 vigour, and finally cause its destruction. Hence it is of great 

 importance that they should be watched by competent foresters. 



The larvae of Scolytidae are said to completely resemble those 

 of Curculionidae : except in the group Platypides, where the body 

 is straight and almost cylindrical, and terminates in an oblique 

 truncation bearing a short hard spine.^ 



Fam. 83. Brenthidae. — Form elongate; rostrum straight, 

 directly continuing the long axis of the locly, often so thick as to 

 form an elongate head; antennae not elhoived. The Brenthidae 

 form a family of about 800 species, remarkable for the excessive 



' Bull. U.S. Dep. Agric. ent. New series, Xo. 7, 1897. 

 2 Pen-is, Ann. Sci. Nat. (2) xiv. 1840, p. 89, pi. iii. 



