MAXILLA. 255 



prevalent number. In the Orthoptera and Trichoptera it Is 

 generally five. These palpi vary very considerably in the 

 size and form of their respective joints, although they are 

 generally slender and filiform : hence they are eminently 

 serviceable in characterizing genera, now that natm'alists 

 have discovered that smallness of size does not form an ob- 

 jection to the value of the characters derived from an organ. 

 In the suctorial mouth, the maxillse are still important 

 organs, although completely changed in the structure : thus, 

 in the Lepidoptera (see fig. 8/), they constitute the two long 

 and very slender instruments which compose the tubular, 

 and, when at rest, spiral apparatus, which the insect employs 

 for collecting honey. That these instruments are really 

 modified maxillae is proved by the modifications which these 

 organs undergo, even in the biting insects, and hkewise by 

 the possession of a minute palpus attached to each at the 

 base, which in most Lepidoptera 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 Pyralidce, they are, 

 however, very distinct; and hence these insects are ortU- 

 narily described as having four palpi. In the Diptera and 

 Hemiptera the maxillae are horny, setiform, or lancet-shaped. 

 In the former order they are sometimes almost obsolete, and 

 are generally furnished 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 Labium, or lower lip. — We have now arrived at a 

 very complicated organ, which generally serves to close the 

 mouth from beneath, and therefore corresponds with the 

 upper lip. This organ, if regarded analogically, with re- 

 ference to the structure of the mouth of other annulose 

 animals, appears to be composed of a pair of maxiUse, united 



