38 PARTIAL QRISMOLOGY. 



The true LEGS, THORACIC LEGS (pedes merely, or pedes veri, PI. II. 

 f. 17), are affixed to the three first segments of the abdomen, and con- 

 sist of several joints, like those of the perfect insect. Each of these 

 joints is inclosed in its peculiar corneous cylinder ; and it is only where 

 these joints are connected, that a flexible membrane completes their 

 union. By means of this arrangement we are enabled distinctly to 

 recognise the joints analogous to those of the perfect insect, so that the 

 leg of a caterpillar may be considered, as truly as that of the butterfly, 

 to consist of the hip (coxa), trochanter (trochanter), thigh (femur), 

 shank (tibia), and foot (tarsus]. It is, indeed, true that these joints, 

 particularly in caterpillars, follow so closely upon each other, from their 

 shortness, that the whole leg has the appearance of a small conical 

 process ; but in many other orders, for example, in the larvae of the 

 Carabodea, the individual joints closely approach in form to those of 

 the perfect beetle. 



In general, all larvae provided with legs possess the true legs, or 

 thoracic legs ; indeed, in most of the larvse of the Coleoptera and 

 Diclyotoptera, these alone are to be found. 



The VENTRAL and ANAL LEGS, or PROLEGS (propedes, pedes spurii, 

 PI. II. f. 18), are short, thick, muscular, unarticulated processes upon 

 the ventral and anal segments of many larvae ; they are exclusively 

 peculiar to this second stage of existence, and entirely disappear upon 

 its transition to the pupa state. In form, they are sometimes short 

 cones, with an obtuse apex ; sometimes longer thin pedicles, distended 

 at their extremity into a flat SOLE (planta) ; sometimes indistinct, very 

 moveable knobs or tubercles, which are protruded or withdrawn at the 

 will of the larva. In these cases, the sole is very generally either half 

 or entirely surrounded by a double or single row of short CLAWS, or 

 crotchets, by the aid of which the caterpillar is enabled to attach itself 

 firmly in climbing ; the tubercles, on the contrary, are mostly unpro- 

 vided with them ; and, indeed, many of the prolegs of the first adduced 

 form do not possess these claws. In many, particularly those whose 

 sole is much distended, it is clapper-shaped, that is to say, composed 

 of an exterior and interior flap, which move in opposition to each 

 other like a pair of tongs, and thus form a claw. Kirby and Spence 

 have constructed a tabular division of larvse from these differences, 

 which we shall here introduce for the purpose of giving a general view 

 of them. 



I. Larvse without feet. 



1. With a membranaceous head of indeterminate shape 

 tera, PI. II. f. 1). 



