THE BUTTERFLY: STRUCTURE OF THE HEAD. 39 



their inner margin to form by tlie junction of the two :i canal, open at the 

 tip and conducting at the base to the oral orifice, and which is kept closed 

 by the interlocking of finger-like plates on the edges of the lateral troughs 

 (87:9,23). In the Hesperidae and next to them the Papilioninae this 

 tongue reaches its maximum length, being sometimes twice as long as the 

 body, while in the Satyrinae and some Lycaenidae it is proportionally 

 shortest, in some cases hardly twice as long as the head. It is furnished 

 at the tip for a greater or less distance with papillae specially developed 

 probably as sense organs, which are nuicli more highly organized in the two 

 higher than in the two lower families, and may by their armature serve 

 to rupture the nectar glands of fiowers (61 :2G-3;3, 311-45,51-57). 



The labium itself is very slightly developed, being simply the frame- 

 work, situated below the oral aperture far removed from the surface, upon 

 which the greatly developed labial palpi are supported ; each side has a 

 cylindrical raised edge, upon which the jointed palpus is seated ; usually 

 this wall is low, but in the groups (such as the Pierinae) bearing a dis- 

 proportionately long basal joint, it is exceedingly produced and itself bears 

 great resemblance to an additional joint. The l(iJ>i(d palpi, on the con- 

 trary, are excessively developed and three-jointed, the second joint being 

 almost invariably the longest and usually much longer than the other two 

 together ; in the Hesperidae it is often very stout. The basal joint is short, 

 excepting in some Pierinae, where it occupies the larger part of the pal- 

 pus ; while the apical joint, usually the shortest as well as the smallest, 

 and sometimes quite minute, is at other times enormously developed, as in 

 t!ie Libytheinae ; in the Hesperidae it is rarely one-fourth as stout as the 

 middle joint, and though always straight, often appears as a mere point 

 projecting beyond the apical hairs of the middle joint. The palpus is 

 heavily clothed with large scales and usually heavily fringed below and 

 sometimes above with a mass of long hairs, ordinarily compacted into 

 a vertical plane, but in the Hesperidae sometimes so arranged, in a thick 

 regular mat of scale-like hairs of unequal length, as to give the palpus 

 a tetrahedral or triquetral appearance. They thus guard the sides of 

 the rolled-up spiral maxillae Avhich they pass in their course ; they are 

 directed upward and sometimes apically forward, clasping the front of the 

 head, the shortest (in the Papilioninae and some Lemoniinae) reaching 

 only as far as the lower edge of the front ; usually they are much 

 longer than the eye and in Hypatus are fully four times its length. The 

 apical joint is usually clothed and fringed to a less extent than the other 

 joints. 



The thorax and appendages. The thorax of buttei-flies, as seen from 

 above, is composed almost entirely of the meso- and metathorax, the pro- 

 thorax being represented only by a pair of bulbous enlargements which I 

 have termed the prothoracic lobes (61 :37), and which are almost always 



