( xlix ) 



the head (PI. LXI. f. 6. 8). The size of the vestigial maxillary palpns is not 

 constant in the family, nor has the palpus always the same shape. The 

 transverse arched stripe of chitin hetween the labial palpi is the raentnm ; in 

 front of it we find often a vestigial, very feebly chitinised submentum. 



The lieforp-mentioned month-])arts of Lepidoptera have attracted much 

 attention on the part of scientific entomologists since AValter's now famous 

 paper on the mouth-parts of }rieroiJti'ri/.r.* The distinctions exiiibited by them 

 within the families of Frenata have, however, not been made use of in 

 classificatory work. The parts are covered by the labial palpi as a rule, and 

 are not visible without pushing tlie paljins away from the iiead. A drop of 

 benzine, or, better, a drop of alcohol, applied to the base, is generally sufficient 

 to make the palpns so flexible that it is movable, and allows the genal 

 process and pilif'er to be studied without injury to the specimen. The two 

 parts of tlie caputal appendices which remain to be discussed, tongue and 

 labial palpus, are better known to the classifier, though the descriptions given 

 of them go seldom beyond length of the former and outline and general aspect 

 of the latter. 



The length to which the tongue has developed in the family Spkingidae 

 is an exceedingly striking character. Here we find the longest tongue of all 

 insects. But what is far more interesting for the student of comparative 

 morphology as well as the classifier is the fact that the length of the tongue 

 varies in this family to such an enormous extent as it does, the extremes 

 being represented by Coci/tius, in which the tongue is sometimes little short 

 of 25 cm., and Poh/ptijckus, where we find species with a tongue represented 

 by two tubercles barely longer than 2 mm. 



A comparative study of the tongue ((/Inssa) of Lepidoptera is a desideratum. 

 It is formed by the first jiair of maxillae, and consists, as is well known, of 

 two halves closely applied to each otlier (PI. LXII. f. 2). Each half is 

 concave on the inner side, and bears at the upper inner edge a very dense 

 fringe of ciliae. The trans-section is in Spkingidae short kidney-shaped, or 

 nearly circular, apart from the inner concave portion. Laterally at the base 

 the tongue has very often a patch of minute hairs ; in a few cases hairs are 

 found all over the dorsal surface. AVithin the cavity of each half we find, in 

 dry specimens, a large trachea and the residue of the dried-up muscles, nerves, 

 etc. The sucking-tube itself (PI. LXII. f. 2, tu) formed by the two halves 

 of the glossa is closed above by the fringe, the ciliae of which are soldered 

 together to form a membrane, which is often quite smooth, showing no trace 

 of transverse striatiou indicating the ciliae. When the tongue becomes reduced, 

 the two halves are less firmly applied to one another, and the transverse 

 Htriation of tlie closing membrane of the tube becomes distinct, till with the 

 fiirtlier reduction of the glossa the two halves separate and the closing 

 membrane assumes tlie form of a fringe of separate ciliae (PI. LXI. f. 11 ; 

 PL LXII. f. 4. 5j, this fringe finally disappearing (PI. LXI. f. ID; PI. LXII. 



• Jen. Zvilsi-hr. Niilurir. v. S, p. I'A (IHSOJ. 



