258 MODERN CLASSIFICATION OF INSECTS. 
part gradually brought from beneath the breast, by means of a joint at 
that part which appears to be its base, lying beneath the jaws, where 
it is furnished with a pair of jointed palpi, until it is stretched out in 
front like the beak of abird. This part now opens laterally (jig. 89. 6.), 
and exhibits not only the two pieces of which it is composed (m 1.), 
but also three organs often of equal length, hitherto concealed within 
it as by a sheath, namely, a delicate central one, transversely striated, 
and two lateral ones, flattened, and very slender, with a central rib, 
and with an articulation beyond the middle, and two minute joints at 
the tip (fig. 89. 10. t). The two horny pieces first noticed as 
forming the external sheath of the tongue are the terminal portions of 
the maxilla, and the feelers at their elbowed base are the maxillary 
palpi; the central striated organ is the labium, and the two lateral 
articulated ones are the labial palpi. We next observe that the 
annulated labium, without any apparent motionof the other parts of the 
mouth, is suddenly thrown out to nearly double its former length (as 
in jig. 89. 8.): this is effected in the following manner; if, whilst re- 
maining in this position, we examine the under side of this apparatus, 
we perceive that the base of the central part arises not from the 
head itself, but from a slender horny tubular piece, which is the 
mentum (fig. 89. 6, 7. 10.,m 2.). On each side of this central part, 
two slender filaments* (paraglossz, z) moreover exist, which, as well 
as the base of the labium itself, are withdrawn into the extremity of 
the tubular mentum (as in fig. 89. 15, 16.), so that the tips alone of 
the paraglossz are visible (16. z). As, however, the muscles at the 
base of these organs are very strong (fig. 89. 17.), the insect is en- 
abled, at will, to throw out the labium and its paraglosse with much 
force to their greatest elongation (as in jig. 89. 8. 10.17.). Another 
peculiarity is at that time observable: the central portion, although 
striated, does not at first exhibit any remarkable hairiness; but no 
sooner is the labium thus thrown out and retained in its situation, as 
it were, by a sort of catch or fastening, than the central part becomes 
distended, the muscles of each ring of which it is composed being 
brought into action, by which means the erection of a whorl of hairs 
upon each ring at right angles (which had previously laid along the 
organ) is effected: this is especially the case near the extremity of 
the tongue. I have often caused this erection of hairs artificially by 
* Analogous to the lateral labial lobes of Tenthredo (fig. 69. 9.). 
