STATES OF INSECTS. 137 



long, and cylindrical, so as exactly to assume the shape 

 of a wooden leg a . These, as in the first class, are ex- 

 panded at the end into a flat plate : but this is wholly cir- 

 cular, is surrounded with claws, and has also in the mid- 

 dle a retractile nipple, as in the preceding class. In 

 Cossus, at least in an American species (Cossus Robinia:), 

 described by Professor Peck b , the anal prolegs have the 

 claws only on their exterior half. 



4. The remaining description of unguiferous prolegs, 

 if they may not rather be deemed a kind of tentacula, 

 are those of certain Diptera, provided with no true legs ; 

 which differ from the three preceding classes, either in 

 their shape, or the arrangement of their claws. In 

 one kind of those remarkable larvae, which from their 

 long respiratory anal tubes Reaumur denominates " rati 

 tailed" that of Elophilus pendulus, there are fourteen of 

 these prolegs, affixed by pairs to the ventral segments, 

 the twelve posterior ones of which are subcorneal, and 

 truncate at the apex, which is surrounded with two cir- 

 cles of very minute claws, those of the inner being much 

 more numerous and shorter than those of the exterior 

 circle ; while the anterior pair terminate in a flat expan- 

 sion, and in shape almost exactly resemble those of a mole c . 

 The prolegs of the larvae of a kind of gnat called by 

 De Geer Tipida amphibia^ and of Syrphus mystaeeus F., 

 (Masca plumata De Geer,) are nearly of a similar con- 

 struction, but in the last are armed with three claws 

 only d . Long moveable claws also distinguish the sin-. 



a Plate XXIII. Fig, 17. 



b Account of Locitst-tree Insect, 1 ;, 69. 



c Reaum. iv. 443. t. xxx.f. G. II. I. xxii./. C. / /. 



d Dc Geer vi. 383. and 137. /, viii./. 8, 9. 



