History and Habits of Pityogenes. 25 
always penetrates the bark at such an angle that when the 
insect assumes this “ guarding position ” the elytral declivity 
is on a line with the surface of the bark. 
While the specimen was in the “ guarding position” it 
was stimulated by touching the hairs very gently with a 
needle, first on one elytron and then on the other. It re- 
sponded by crowding as close as possible to the burrow on 
the side stimulated. This response again would be most 
effective in guarding against small predaceous or parasitic 
insects. When the elytron was touched firmly with the needle 
the specimen immediately retreated into the burrow as far 
as it could go. 
Response to Warrer.— A small drop of water was then 
placed over the entrance of the burrow and allowed to enter 
by letting out a bubble of air with the needle. The worker 
immediately backed upward, closing the entrance and remain- 
ing motionless, with the tip of the elytron out of the water. 
More water was added from time to time so that the insect 
and the entrance was entirely covered. While these conditions 
lasted- he made no response to mechanical stimuli and was 
not induced either to leave his burrow or to retreat farther 
into it. The entire body of the insect was kept covered and 
the burrow filled with water for fifteen minutes, when it was 
allowed to evaporate and to seep into the wood. Very shortly 
after the water had sunken below the end of the abdomen 
slight movements were observed and on stimulating with a 
needle some response was obtained. Three minutes later he 
was quite active, moving abdomen and elytra considerably, 
apparently renewing the air supply and drying out the space 
between abdomen and wing covers. This continued for about 
two minutes, when he retreated into his burrow and resumed 
work. 
Similar experiments were tried with another specimen, the 
burrow of which was not advanced so far, only about half of 
the body being covered. He seemed disturbed at first but 
continued to work although the hole was entirely filled 
with water and all of his body but the tip of the abdomen was 
covered. Soon he backed out bringing a considerable amount 
