History and Habits of Pityogenes. 93 
On returning from dinner, however, the burrow was found 
to be occupied by another specimen easily distinguished by 
its much lighter color. Evidently he had been working some 
time as his prothorax was completely hidden. He continued 
to work steadily throughout the afternoon and when observa- 
tions ceased for the day at 5 p. m., slightly over half of his 
body was in the burrow, the margin extending midway be- 
tween the middle and hind legs. The middle legs were now 
in the burrow and the hind legs were braced against the sur- 
face of the bark. He apparently continued work through- 
out the night, as at 8 a. Mm. the following morning, the burrow 
had been extended so his hind legs were completely hidden 
and only the last four segments of the abdomen were visible. 
(Shghtly farther than shown in Fig. 9.) 
He now apparently began changing the course of the 
burrow so it gradually came to extend more and more parallel 
to the surface of the bark. By the time observations ceased 
for the day he had penetrated so far that the body was en- 
tirely below the surface, but the posterior end of his body 
was still visible. He again continued work all night as shown 
by the fact that by the next morning the burrow had advanced 
so far in a direction parallel to the surface that only the end 
of his body was visible on looking into the opening (Fig. 
10). The end of the elytra, perhaps one-fourth of them, 
could still be seen by concentrating the light and directing 
it into the entrance. In burrowing he still rotated in the 
burrow working as well upon his back (Fig. 11) or sides as 
in an upright position. As the bark was burrowed out, the 
bits of frass were passed backward by the hind legs. As this 
material piled up behind him and on top of him he would 
back up to the entrance of the burrow, forcing it upward 
where it adhered to form a sort of dome over the burrow. 
When this was touched with a needle it would topple down 
upon him and he would immediately back up and force it 
out again. Although he was teased for five minutes or more 
by toppling the borings in upon him as soon as he had re- 
tired into his burrow, he always immediately backed upward 
until the end of his abdomen protruded slightly from the 
