THE EXTERNAL STRUCTURE OE THE L.EPIDOPTEROUS LARVA. 37 



Unilateral ' Macro ' type " (Trans. Ent. Soc. London, 1893). Prout 

 has noticed that, in the Geometric! genus Oporabia, the newly-hatched 

 larva has a complete circle of hooks. 



We have already mentioned that the segments which usually bear 

 the prologs are the third, fourth, fifth, sixth and tenth abdominal. 

 The Geometrids, however, usually have them only on the sixth and 

 tenth abdominal segments. In the early stages of many Noctuid 

 larvae, we find, however, only the merest traces of prolegs on the third 

 and fourth abdominal segments ; these, however, usually develop com- 

 pletely at the later ecdyses. The peculiar method of progression, 

 characteristic of Geometrid larvae, is due entirely to the absence of the 

 prolegs on the third, fourth and fifth abdominal segments, and those 

 Noctuid larvae which do not develop prolegs on the third and fourth 

 abdominal segments, until late in life, resemble the Geometrid larvae 

 in their mode of progression, whilst a whole group of Noctuid moths, 

 which never do develop them, retain the looping habit throughout, and 

 have been called, on this account, by some entomologists, Hemi- 



GEOMETERS. 



In some Geometrid larvae, prolegs appear on other than the abdo- 

 minal segments normally carrying them. The larva of Himera pennaria 

 obtains a pair of ill-developed ones, on the fifth abdominal segment, at 

 the first moult ; these persist after the second and third moults and 

 disappear with the fourth moult. In larvae of Anisopteryx aescularia, 

 prolegs are developed on the same segment, but these continue through- 

 out the whole larval existence. 



The larva of an American moth, Lagoa crispata, described as being 

 like a hairy Limacodid (Heterogenea) larva, with the head retracted, the 

 body short, and the legs so rudimentary as to impart a gliding motion 

 to the caterpillar when it moves, has seven pairs of short abdominal 

 prolegs, the second and seventh abdominal segments each bearing a 

 pair of rudimentary prolegs, in addition to those which normally carry 

 them. Burmeister found exactly similar prolegs on the second and 

 seventh abdominal segments of Chrysopyga undulata. According to 

 the figures of Kowalewski and Tichomiroff, the embryonic larvae of 

 Sphinx and Bombyx mori have, at first, a pair of prolegs on each abdo- 

 minal segment, but half of these are absorbed again before the larva 

 hatches. 



Some very peculiar methods of progression are to be noticed among 

 the larvae of certain species of lepidoptera, none, however, is more peculiar 

 than that of the Cochliopodids, of which our two British species, Hetero- 

 genea cmciata (asella) and Apoda avellana (testudo) are very fair 

 representatives. Resting on the upper surface of the leaves of their 

 food-plants, with the body inflated to form a dome-like structure, 

 they look very little like lepidopterous larvae, and bear, in fact, a 

 strong resemblance to the pupae of ladybirds (Coccinellidae). The 

 almost evanescent character of the prolegs makes progression on the 

 smooth upper surface of a leaf difficult, and Poulton has suggested 

 that the remarkable undulatory movement by which the Cochliopodid 

 larvae now progress was due originally to the larvae first walking " with 

 adhesive claspers," that these gradually became shorter and broader, 

 thus yielding increased support by extending the area by means of which 

 they adhered. Finally the claspers, he considers, would be altogether 

 lost, and the whole of the ventral surface, from which they formerly 



