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Scientific American Supplement, No. 388, June 9, 1883 by Various
page 134 of 156 (85%)
terminate blindly, a mature beetle being usually found in the end of
each. Sometimes, but rarely, one or more of those vertical excavations
is found to extend farther, and, bending at a right angle, to take a
turn around the circumference of the bush, thus constituting a second
horizontal circular canal from which, as from the primary one, a
varying number of short vertical tubes branch off. And in very
exceptional cases these excavations extend still deeper, and there may
be three, or even four, more or less complete circular canals. Such an
unusual state of things exists in the specimen from which Fig 3 is
taken.

[Illustration: FIGS. 3 and 4--Mines of Corthylus
punctatissimus.]

It will be seen that with few exceptions, the most important of which
is shown in Fig 4, all the excavations (including both the horizontal
canals and their vertical off shoots) are made in the sap-wood
immediately under the bark, and not in the hard and comparatively dry
central portion. This is, doubtless, because the outer layers of the
wood are softer and more juicy, and therefore more easily cut, besides
containing more nutriment and being, doubt less, better relished than
the drier interior.

This beetle does not bore, like some insects, but devours bodily all
the wood that is removed in making its burrows. The depth of each
vertical tube may be taken as an index to the length of time the
animal has been at work, and the number of these tubes generally tells
how many inhabit each bush, for as a general rule each individual
makes but one hole, and is commonly found at the bottom of it. All of
the excavations are black inside.
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