( xHs ) 



the head (PI. LXI. f. 6. 8). Tlie size of the vestigial maxillary ]ialpns is not 

 constant in the i'amily, nor has the ])alpns always the same sliape. Tlie 

 transverse arched stripe of chitin between the labial palpi is the mentnm ; in 

 front of it ^e find often a vestigial, very feebly chitinised submentam. 



The before-mentioned month-parts of Lepidoptera have attracted much 

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

 paper on the mouth-parts of Miero/iti'ri/.r.* The distinctions exhibited by them 

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

 classificatory work. Tlie parts are covered by the labial palpi as a rnle, and 

 are not visible without jiushing the palpus away from the head. A drop of 

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

 to make the jialpus so flexible that it is movable, and allows the geual 

 jirocess and pilifer to be studied without injury to the specimen. The two 

 jiarts of the cajnital appendices which remain to be discussed, tongue and 

 labial palpus, are better known to the i;lassifier, though the descriptions given 

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

 of the latter. 



The length to wiiich the tongue has developed in the family Sjjliinyii/ae 

 is an exceedingly striking character. Here we find the longest tongne 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 Coe^titis, in which the tongne is sometimes little short 

 of 25 cm., and Poli//jt'/c/t>fs, where we find species with a tongue represented 

 by two tubercles barely longer than 2 mm. 



A comparative study of the tongue (j/los.sa) of Lepidoptera is a desideratum. 

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

 two halves closely applied to each other (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 Spldngidae short kidney-shaped, or 

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

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

 found all over the dorsal surface. Within 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 (PL LXIL 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 (pite 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 

 striation of the closing membrane of the tube becomes distinct, till with the 

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

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

 PI. LXII. f. 4. .3), this fringe finally disappearing (PL LXI. f. K) ; PI. LXII. 

 * Jen. Zeitschr. Naturw. v. 5. p. 751 (1885). 



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