274 MR. P. H. GOSSE ON THE CLASPING-OliGANS 



a triangle, of which the base is the edge of the seventh segment, the sides are often 

 incurved, and the point is, in general, prolonged into a strong, horny spine ; e. g., Orn. 

 Amphrysus, P. Merope, Erechtheus. This point, however, varies much, in different 

 species, in length, breadth, sharpness, curvature, and direction ; and, as it is one of the 

 elements of the prehensile apparatus which I am proposing to describe, I distinguish 

 it by the term uncus, a drag-hook. The term "tegumen," adopted by Dr. White, seems 

 hardly appropriate for this spinous, often wiry, point, which is certainly in no sense a 

 cover. But it does express the function of the wide annular part of the segment, from 

 which the uncus projects ; and in this sense I use it. 



Viewed from the side, the tegumen and uncus together often present a very curious 

 resemblance to the skull of a bird without the lower mandible, e. g. Erechtheus, 

 Demoleus; which latter, however, is simulated occasionally by the scaphiwm, so as to 

 complete the likeness — Deiphontes, Homerus, Childrcnce, and very curiously in Tarn. 

 Apollo. I occasionally avail myself of this and like accidental resemblances, for more 

 definite and graphic description. 



The extreme point is generally somewhat swollen and flattened, spoon-wise — and this 

 even when the organ is of a wiry slenderness, as in Bhodifer. Sometimes it is bifid — 

 Agamemnon, Poly dorus; more rarely even trifid — Argesilaus, Archesilaus; sometimes 

 it is curved upward — Agamemnon; sometimes vertically downward — Sector, Lycidas, 

 Agavus ; sometimes it is short, thick, and uncouth — Antenor, Zalmoxis, Bromius ; almost 

 straight — O. Arruana, P. Hesperus, Bhodlfer; often nearly a half-hoop of very slender 

 wire, displaying a strength, elasticity, and polish, almost of steel — Vertumnus, Macedon, 

 Turn as. The receding margins are often turned up to a height that considerably exceeds 

 the plane of the dorsal surface, which then becomes transversely concave — Mayo, 

 Machaon, Zalmoxis, Merope ; this surface is sometimes indented Avith a trilateral 

 (Antenor) or quadrilateral (Agesila/is) depression. Often it is clothed with a median 

 ridge of long and close-set hairs, which project horizontally, and, so to speak, thatch the 

 cavity and its organs — e. g. Agamemnon, Codrus, Homerus, and, signally, Diphilus, and 

 the abnormal Hector group, though here there is no uncus. More commonly the stiff 

 ridge-hairs are evect--Erechthem, Bhetenor, Merope; or, at first erect, and then arching 

 forward — Menestheus, Machaon . 



When the valves arc perfectly developed, as in Ornithoptera, the uncus is projected 

 immediately under the line produced by the meeting of the dorsal edges of the valves ; 

 and then the median ridge of long hair helps to fill the blank space between. 



The inferior surface of the uncus usually bears two conspicuous laminte descending 

 vertically from it, more or less deep, which take their origin insensibly near the point, 

 and increase in depth gradually — Erechtheus, Bhetenor, Helenus, Merope, following the 

 curvature of the margius till they are lost in the descending rami ; but in some cases this 

 keel begins at some distance from the point, and with its full depth — Deiphontes, Homerus. 



On each side, near the spot at which the rami of the keel can no longer be distin- 

 guished, a conspicuous horny tooth often projects horizontally from the edge of the 

 segment — Helenus, Tv/rnus. 



The uncus is apparently composed of nearly pure chitine, whose varying density is 



