19 



Fig. 10. — XyltA .. Female and 



nude— enlarged (original). 



THE GENUS XVLtBOPJ 



This genus embraces a large number of Bpecies, the classification of 



which presents great difficulties, and is at .present in much confusion. 



The females in some groups are nearly indistinguishable, and although 



the males present recognizable differences, they are in most of the 



species entirely unknown. The males 



differ remarkably from the female-: 



they are wingless, and often very much 



smaller. They are, moreover, much less 



numerous than the females, and, as they 



seldom leave the galleries in which they 



were born, are very rarely collected. 



The lt pubescens n group, — Fig. 10 repre- 

 sents, respectively, the male and female 

 Xyleborus pubescent Zimm. Under this 

 name are confused the females of sev- 

 eral species which have the same habits. 



A solitary female starts the colony, the plan of which is given in 

 fig. 11. The branches serve as brood galleries, and in each are d< 

 ited 5 or G oval pearly eggs. The young hatch out within a week and 

 begin at once to feed upon the ambrosia, which glistens upon the walls 

 like hoarfrost. The pupa,* are formed lying free in the galleries, and 



in somewhat over a 

 month from the 

 the perfect beetles 

 make their appear- 

 ance. In time the 

 colony contains, 

 besides the mother 

 insect, 15 or 20 <>t' 

 her offspring which 

 have become adult. 

 Nearly all of these 

 will be females. 

 Only one or two 

 males are commonly 

 found in a colony. 

 The males fertilize 

 their brood sisters 

 Fm. ii. —Gallery «t A teen* in orange— natoralaise (original), within the "'lller- 



ies, and by them a second generation may be start 'd. But usually the 

 seasoning of the wood and the threatening failure of food fungus warn 

 the young females to depart and seek fresher tree trunks in which to 

 found new colonic-. 

 The swarming of the females leaves tlie abandoned males in sad 



