Scientific American Supplement, No. 388, June 9, 1883 by Various
page 134 of 156 (85%)
page 134 of 156 (85%)
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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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