132 STATES OF INSECTS. 



while those of Tcnlhredo and Sirex in the order Hymm- 

 optera are furnished with these organs. At present I 

 know no Dipterous larva that may be said to have real 

 leo-s, unless we are to regard as such certain tentacula 

 formed upon a different model from the legs of other lar- 

 vae a . Rosel has, I think, figured a Lepidopterous apode* 

 No Neuropterous one has yet been discovered. 



The legs of larvae are of two kinds \ either horny and 

 composed of joints, or fleshy and without joints b . The 

 first of these, as I observed in a former letter c , are the 

 principal instruments of locomotion, and the last are to 

 be regarded chiefly as props and stays by which the ani- 

 mal keeps its long body from trailing, or by which it 

 takes hold of surfaces ; while the other legs, or where 

 there are none, the annuli of its body, regulate its mo- 

 tions. The former have been commonly called true legs 

 {pedes veri), because they are persistent, being found in 

 the perfect insect as well as in the larva ; and the latter 

 spurious legs (pedes spurii), because they are caducous, 

 being found in the larva only. Instead of these not very 

 appropriate names, I shall employ for the former the 

 simple term legs, and for the latter prolegs (propedes) d . 

 .."The. legs, when present, are always in number six, and 

 attached by pairs to the underside of the three first seg- 

 ments of the trunk. They are of a horny substance, and 

 consist usually of the same parts as those of the perfect 



a De Geer iv. 5. Legs of this kind are figured Plate XXIII. 

 Fig. 7. 



b In the larva, however, of Sialis, or some kindred genus, in which, 

 like those of Scolopendra, the prolegs are jointed, a pair distinguishes 

 each abdominal segment. See Reaum. iv. t. xv.f. I, 2. Compare De 

 Geer ii. t. xxiii./. 11. 



c See above, Vol. II. 28G— . <i Ibid. 288. 



