710 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



the female api)arently responding by moving back and forth in her 

 mine. After a moment or two the male visited another female in her 

 hole and caressed her in the same manner, then returned to the first 

 female and inserted his intromittent organ in the female, the end of 

 whose body was depressed, so as to leave a space between it and the 

 end of the elytra. Union continued for six minutes, during which time 

 the hiudermost pair of feet of the male kept stroking the end of the 

 abdomen of its mate, while its antenute were vigorously moving. At 

 the end of this time it immediately withdrew and disappeared down 

 another hole, the female descending her mine. From these facts we 

 infer that the male of this species is polygamous. 



While boring, at least in con- 

 finement, the borings or dust are 

 thrown out around the mouth of 

 the mine in a heap. The mine 

 or tunnel is from an inch to an 

 inch and a quarter long ; at close 

 intervals on one side there are 

 lateral deep notches in which two 



Fig. 243.-a, mine of Uylurgops pinifex, with eggs, *» ^^^CC Or foUr CggS are irrCgU- 

 6, mine with young larva> ; c, mine of Xyleborus larlv laid J Or the CggS are Care- 

 c<.latus. with eggs. Gissler del. ^^^jj^ ^igpositg^ ^^^^^ ^^. gi^j^ . ^he 



lateral notches are then filled with borings or dust by the movements 

 of the female in her main tunnel, the eggs being inclosed in the mass 

 of borings. (Fig. 243.) 



Hylurgops does not make lateral notches, but places her eggs side 

 by side in a single recess on one side of the mine.* 



This and the other bark-beetles of the pine have numerous insect 

 enemies which wage incessant war upon them. Various species of 

 small beetles pertaining to the families StaphyUmdce, Histerklce, etc., 

 are always to be met with under the loose worm-eaten bark of pines, 

 and M. Perris has ascertained that these insects resort to this situation 

 for the purpose of rearing their young, their larvae being predaceous 

 and subsisting upon the larvae and pupae of the bark-beetles. (Fitch.) 

 We have found this species common under the bark of pines in Maine, 

 the beetles flying in April and May. 



39. Xyleborus piibescens Zimraennan. 



"Among a large colony," remarks Mr. Schwarz [1. c, p. 41), "of this 

 beetle which I found boring into Pinm inops near Washington, I dis- 

 covered two specimens of the male." The difference in general appear- 

 ance between the two sexes is very striking. 



* See Third Report U. S. Entomological Commission, Chapter X, p. 280, 1883. Cora- 

 pare also Schwarz iu Proc, Entomological Society of Washington, I, p. 47. 



