790 Bulletin American Museum of Natural History. [Vol. XXIII, 



genus Platypus, though best represented in the tropics, contains several of 

 the largest and most destructive species in the United States. "They are 

 powerful excavators, generally selecting the trunks of large trees and driv- 

 ing their galleries deep into the heart-wood. They do not attack healthy 

 trees but are attracted only by the fermenting of the sap of dying or very 

 badly injured trees. The death rattle is not more ominous of dissolution 

 in animals than the presence of these beetles in standing timber. . . .The 

 female is frequently accompanied by several males and as they are savage 

 fighters, fierce sexual contests take place, as a result of which the galleries 

 are often strewn with the fragments of the vanquished. The projecting 

 spines at the end of the wing-cases are very effective weapons in these fights. 

 With their aid a beetle attacked in the rear can make a good defense and fre- 

 quently by a lucky stroke is able to dislocate the outstretched neck of his 

 enemy. The females produce from 100 to 200 elongate-oval pearl-white 

 eggs, which they deposit, in clusters of 10 or 12, loosely in the galleries. 

 The young require five or six weeks for their development. They v.'ander 

 about in the passages and feed in company upon the ambrosia which grows 

 here and there upon the walls. . . .The older larva? assist in excavating the 

 galleries, but they do not eat or swallow the wood. The larvse of all ages 

 are surprisingly alert, active and intelligent. They exhibit curiosity equally 

 with the adults, or show evident regard for the eggs and very tender young, 

 which are scattered at random about the passages, and might easily be 

 destroyed by them in their movements. If thrown into a panic the young 

 larvse scurry away with an undulatory movement of their bodies, but the 

 older larvse will frequently stop at the nearest intersecting passage and 

 show fight to cover their retreat." The ambrosia of P. compositus Say 

 consists of hemispherical conidia growing in clusters on branching stems. 

 The long continued grovvlh of this fungus blackens the walls of the older 

 galleries. 



Xyleborus saxeseni Ratzb., instead of producing ramifying galleries, 

 excavates in hardwood trees (oak, hickory, beech, maple) a flat, leaf-shaped 

 brood chamber connected with the surface of the bark by one or a few 

 tubular galleries. The chamber "stands vertically on edge, parallel with 

 the grain of the wood. The space between the walls is not much greater 

 than the thickness of the bodies of the adult beetles. The larvje of all ages 

 are able to cling to the vertical walls, and to progress over them by an adapta- 

 tion of the end of the body which aids them in progression. The entire 

 surfaces of the walls in the brood chamber are plastered over with ambrosia 

 fungus. It consists of short erect stems, terminating in spherical conidia. 

 The freshly grown fungus is as colorless as crystal, but it is usually more 

 or less stained with greenish yellow, and sometimes resembles a coating 



