1870.1 105 
extent as to bury the mouth of the burrow ; and, if the frass should be 
matted together by being wetted, the burrow often extends through it to 
the surface, occasionally forming a tubular addition of an inch or more 
in length, but this is a purely accidental occurrence. 
I had the good fortune on one occasion to observe the process of 
separating this splintery variety of frass. Ihad so split a piece of wood 
as to expose a burrow within a few lines of its inner extremity. In 
this burrow was a beetle that could not in these circumstances com- 
pletely hide itself. It continued, however, to work, and kept ejecting 
frass of this description. It moved very gently, as beetles do when 
moving their jaws, with the exception that every ten seconds it came out 
with a sudden jerk for a distance equal to one-third its own length; so 
one could not help concluding that something it was pulling at had 
suddenly given way. I think that I am justified in inferring from this 
that these little splinters are bitten through at one or both ends, and 
then laid hold of and separated by a pull ending in the sudden jerk result- 
ing from the bit of wood becoming loose, 
I may mention that, when perfect, the beetle has very long slender 
tarsi, and that it is a matter of notoriety that these are usually broken. 
This is almost invariably the case with those beetles that have formed a 
burrow ; they often possess no tarsi whatever, except about half of the 
basal joints. It occurred to me that this sudden jerk sufficient explained 
the want of tarsi. Such a beetle, when extracted from his burrow, is 
utterly helpless, yet in this state he manages to run backwards and 
forwards in his burrow with great facility, and to live there in apparent 
health for many months; moreover, as he never naturally leaves the 
burrow again, the loss must be of but little consequence. The newly- 
emerged beetles, that is, those possessing their long and delicate tarsi, 
do not seem comfortable on a smooth surface, but over a rough piece of 
bark they can run with great agility. I suspect, though on this point 
I have made no observations, that they find them very useful in sus- 
taining the body in a proper position at right angles to the surface of 
the wood or bark in commencing their burrows. As to the mechanism 
of this jerk by which the splinters are separated, the anterior femora 
are extremely broad (or, rather, deep), from which circumstance indeed 
the genus is named; and they are not by any means narrowed in the 
other diameter, but are extremely strong limbs ; the anterior tibiz are, 
externally, diagonally ridged, but in such a way that, though the ridges 
are diagonal to the tibia, they are, when it is in its usual position, 
transverse to the burrow, and are sharpest forwards, so that they must 
give a very firm hold of the wall of the burrow when the beetle uses 
his strong femoral muscles to push himself backwards. 
