4 BURGESS ON THE ANATOMY 



To the slightly concave lower edge of the clypeus is soldered the upper lip, or labrum 

 {lb.), a small, flat triangular piece, with a somewhat projecting apex, which overlies the 

 base of the proboscis. On either side the labrum, and soldered to the cheeks, are seen 

 two small triangular, almost thorn-like, pieces, the rudimentary mandibles (md.). They 

 are immovable and of course functionless ; their inner margin bears a row of stiff bristles. 

 Behind the mandibles are the maxillae (mx.), of compensatingly enormous development, 

 forming the tubular proboscis, used by the insect to suck up the honey or other vegetable 

 juices forming its food in the imago stage. 



Each maxilla is a long, slender, flexible organ, tapering gently to the tip, and having a 

 deep groove along its inner surface, which surface being applied to that of the opposite 

 maxilla, and locked in that position by hooks provided for the ^purpose, a canal is formed 

 traversing the proboscis from base to tip. When not in use the proboscis is coiled into h 

 spiral like a watch spring, and lies under the head, protected on either side by the large 

 hairy labial palpi, which are specially developed for this service. In the Milk-weed But- 

 terfly the proboscis is about 15 mm. long, and at the base, about 0.6 mm. wide. The tip is 

 rather bluntly pointed. Superficially (pi. 2, fig. 8), the proboscis presents a sort of coat of 

 mail appearance from its composition of an immense number of rings, or rather segments 

 of rings, since a portion on the inner side is of course wanting. The separation of these 

 rings by intervening and more yielding spaces of cuticle, is evidently to permit the spiral 

 coiling of the proboscis, while imparting at the same time the necessary stiffness. The 

 rings are not perfectly regular, but are here and there broken, or branch and anastomose. 

 They are themselves made up of quadrangular plates joined side to side, except near the 

 inner edges of the maxillae, where, especially in front, they become separated, more or less 

 hexagonal and irregularly scattered ; on the hinder side each plate sends off a stout, spine- 

 like process, which is directed inwards (see fig. 10). These plates, as will be seen in sec- 

 tions of the proboscis (figs. 9, 10 and 11), are the bases of little pyramids, or in some 

 regions, stout nail-shaped bodies imbedded in the cuticle, each one m its own prismatic 

 block of cuticle, which probably corresponds to a single underlying hypodermic cell, its 

 matrix. The blocks may occasionally be demonstrated by the separation of one of them 

 from its neighbor in the process of section cutting, (fig. lie). The dividing boundary line 

 between the blocks can also generally be seen in successful sections (see figs. 11a, b and c ; 

 Gu. cuticle, and hy. hypoderm). The cuticular lamination too is evident in such sections. 

 The pyramids are opaque, black, or dark brown, and the rest of the blocks colorless and 

 transparent. 



Dotted over the surface of the proboscis but more thickly toward the tip are little cir- 

 cular plates with a minute papilla in the centre (see fig. 8). These are regarded as modi- 

 fied hair structures, and in many butteifiies are curiously and greatly developed,^ forming 

 toothed or notched spines, believed by Breitenbach to serve as the teeth of a saw or file, 

 enabling the insect to work the proboscis through plant tissues in search of the contained 

 juices. These organs are reenforced in the case of the Orange moth {Ophideres fullonica), 

 by large spines developed from those which serve simply to lock the maxilla together in 



1 See Breitenbach, Katter's Entomol. Nachr. v, 238; Report on Cotton Insects, U. S. Agric. Dept. 1879, p. 86 

 Arch. Mikr. Anat., xv, 8 and xvi, 308. Also F. Darwin, (proboscis of Aletia). 

 Quart. Journ. Mier. Sci., xv, 385, and F. J. Comstock's 



