Tlistory and Habits of Pityogenes. 21 
(Fig. 7) except when gouging out the center of the bottom 
of the burrow, when he assumes a position as nearly parallel 
to the bark as the depth of the burrow will allow. As the 
hole became somewhat deeper, this part of his work becomes 
harder and this new difficulty is solved by making the burrow 
slightly wider a short distance below the surface (Fig. 8). 
It is apparently quite important that the entrance to the 
burrow be as small as possible. It is made just large enough 
to admit the insect and can then be guarded much more 
readily as we shall see later. 
By the time the prothorax was one third submerged, the 
green inner bark was reached. This was quite sticky and 
pitchy and the borings frequently adhered to the legs, ham- 
pering them considerably. This material was passed up out 
of the burrow by movements of the head assisted at times by 
the fore legs. It was received by the middle legs which 
attempted to deposit it at the edge of the burrow. How- 
ever, this frass often adhered and on attempting to clear it 
away with the hind legs both pairs soon became clogged with 
the sticky material. After trying in vain to free his legs of 
this incumbrance, he backed out of his burrow and took a 
short jaunt, kicking his legs and dragging them over the 
surface of the bark, in much the same way as a boy will free 
his feet of mud. This was entirely successful and he im- 
mediately returned to work. 
The worker now assumed a position which allowed freer 
observation of the action of the mouth parts and head. With 
the prothorax pressed against one side of the burrow and the 
fore legs braced against the other side, the mandibles were 
pressed into the bark and by a rapid twist of the entire 
head a small bit was removed. The frass often adhered to 
the mandibles hampering them badly. The head was then 
turned upward to the margin of the opening and the bits 
of pitchy park were removed by a cleaning motion of the 
maxillae. These moved very freely both laterally and 
antero-posteriorly with a sort of plunger-like movement. 
The fact that the lacinal teeth or hairs are flattened (Fig. 
19) must aid greatly in the performance of this function as 
