INSECT. 



853 



occupies the space between this and the membrane 

 which runs parallel therewith, forming the basal part 

 of the internal terminal lobe (d). Conjointly these 

 three pieces (b, c, $ d) are termed the stipes or stalk 

 of the maxillae by MacLeay and Kirby. The last of 

 these, or the fourth piece of the maxillae (d), is more 

 important, extending not only along the internal side 

 of the maxillae, but extending often considerably be- 

 yond the former pieces, and being very variable in its 

 Form ; its terminal portion (d d) has been named the 

 internal lobe of the maxillae by MacLeay and others, 

 but it is not distinct from the basal part (d). In 

 the predaceous beetles it is long, slender, curved at 

 the tip, and internally clothed with fine hairs or 

 bristles, and sometimes terminated by a hook, which 

 is occasionally articulated, as in the tiger-beetles. 



Pigs. 102, Maxilla of Cicindela ; 103, ditto of Bamfais ; 104, ditto 

 of Blatta ; 105, ditto of Melvluntha. 



This part is termed the piece mtermaxillaire by 

 Strauss-Diirckheim, and lacinia by MacLeay. In 

 some biting insects it is of a very large size, as in the 

 bees, in which it forms the sole terminal lobe of the 

 maxillae (fig. 103) ; in many instances, however, it is 

 greatly reduced in size, not extending beyond the 

 base of the palpus, in which case another organ is de- 

 veloped at its expense, which, as in the large water 

 beetle (Hydrous picem], joins the terminal part of the 

 maxillae (figs. 99, 100, 101 e). In the predaceous 

 beetles this external lobe, as it is generally called, is 

 often of equal size with the terminal portion of the 

 lacinia, or the internal lobe, and is here articulated 

 both at its base and in the middle (fig. 102 e e), and 

 is generally termed thence the internal maxillary 

 palpus. In the order Ortlioptera, this same outer lobe 

 is equally developed, but is not articulated, except at 

 the base (fig. 104) ; its inner surface is somewhat 

 hollowed, so that it falls upon the terminal lobe of 

 the lacinia, and defends it laterally. It is hence 

 termed by Fabricius the galea, a term applied theo- 

 retically by Strauss-Diirckheim to the outer lobe of 

 the maxilla; of all insects. In many insects the two 

 lobes are soldered together into a large flattened 

 membranous plate ; numerous other variations of form 

 occur in these two lobes, which, from their situation, 

 are necessarily the part most serviceable to the insect, 

 and consequently modified and adapted to the func- 

 tions and habits of each of these variations ; perhaps 

 the most remarkable are those exhibited by some of 

 the leaf-devouring lamellicorn beetles, in which the 

 extremity of the lobes are very broad, horny, and 

 armed with several strong teeth, having somewhat 

 the appearance of a large double tooth (rig. 105), and 

 by some other beetles which feed upon the pollen or 

 honey-flowers, and in which the outer lobe of the 

 maxillae are nearly half the length of the body. In the 

 stag-beetles it is prolonged into a fine pencil of hairs, 

 serviceable in licking up flowing sap. It is at the exter- 

 nal extremity of the stipes, and intermediate between 



it and the base of the outer lobe of the maxilla, that 

 thepalptis (for mp) of each maxilla is attached. This 

 is a slender appendage, somewhat similar in its con- 

 struction to the antennas, but much shorter, and com- 

 posed of fewer joints, varying in the latter respect 

 from one to six articulations; I he latter number is 

 often found in the Hymennptera, but in the Coleoptera 

 four appears to be the prevalent number. In the 

 Orthoptera and Trichoptefa it is generally rive. These 

 palpi vary very considerably in the size and form of 

 their respective joints, although they are generally 

 slender arid filiform ; hence they are eminently *er- 

 viceable in characterising genera, now that naturalists 

 have discovered that smallness of size does not form 

 an objection to the value of the characters derived 

 from an organ. In the suctorial mouth, the maxilla? 

 are still important organs, although completely 

 changed in the structure; thus, in the Lepidoptera 

 (see fig. 87), they constitute the two long and very 

 slender instruments which compose the tubular and, 

 when at rest, spiral apparatus, which the insect em- 

 ploys for collecting honey. That these instruments 

 are really modified maxillae is proved by the modifi- 

 cations which these organs undergo, even in the 

 biting insects, and likewise by the possession of a 

 minute palpus attached to each at the base, which in 

 most Lcpiduptera is so small as to be easily overlooked, 

 being concealed by the hairs of the labial palpi ; in 

 other moths, especially in some of the PyratidcE, they 

 are, however, very distinct; and hence these insects 

 are ordinarily described as having lour palpi. In the 

 Diptem &nd~Hcmiptera the maxilla; are horny, scti- 

 form, or lancet-shaped. In the former order they 

 are sometimes almost obsolete, and are generally fur- 

 nished with a palpus, varying in the number of its 

 joints from five to one, but in the latter they resemble 

 the mandibles, and are not palpigerous. In the flea 

 they are dilated and palpigerous. In the Trichoptera 

 they are rudimental, but furnished with long palpi. 



The Labiuw, or tower Up. We have now arrived at 

 a very complicated organ, which generally serves to 



110 



Fig's. 106, Labium of Cnrnbus outside: 107, ditto inside; 108, 

 ditto laterally; log, ditto of Necrophaffus ; 110, ditto of Dy lints* 



close the mouth from beneath, and therefore corres- 

 ponding with the upper lip. This organ, if regarded 

 analogically, with reference to the structure of the 

 mouth of other annulose animals, appears to be com- 

 posed of a pair of maxillaj, united together internally, 

 furnished with a pair of palpi, and covered, in a great 

 measure, by a large horny plate, which is generally 

 termed the mentum. The parts of which this organ 

 is composed are numerous, and the greatest confusion 

 has arisen in the works of authors, as to their nomen- 

 clature, owing to the numberless modifications which 

 they undergo, whereby the relative proportions and the 

 consequent relations of the various parts with each 

 other, and with the head, are greatly altered. On 



