710 FIFTH REPORT OP THE ENTOMOLOGICAL COMMISSION. 
the female apparently responding by moving back and forth in her 
mine. Altera moment or two the male visited another female in her 
hole and raivssed 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 hindermost pair of feet of the male kept stroking the end of the 
abdomen of its mate, while its anteunaB 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 
tj- a inch and a quarter long ; at close 
intervals on one side there are 
■&* lateral deep notches in which two 
Fig. 243. -a. mine of Hylurgop* pini/e*, with egg S; to tbree 0r four e ^ S are irre S U - 
b, mine with young larvae; c, mine of Xyieboru* larlv laid ; or the eggs are care- 
«**», with eggs. Gissler del. faUy deposited gide by side . fche 
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 miue.* 
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 Staph ylini (he, Histeridce, 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 larva3 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 pubescens Zimmerman. 
"Among a large colony," remarks Mr. Schwarz (/. c, p. 41), "of this 
beetle which I found boring into Phius inops near Washington, I dis- 
covered two specimens of the male." The difference in general appear- 
ance between the two sexes is very strikiug. 
* See Third Report IT. S. Entomological Commission, Chapter X, p. '280, 1S83. Com- 
part' also Schwarz in Proc. Entomological Society of Washington, I, p. 47. 
