70 BRITISH BUTTERFLIES. 



caterpillars of their size, other colours would be too conspicuous for 

 their advantage, and variation in this direction would be natural. 

 Moreover, it is the colour reached, or partly reached, in several 

 different ways, as the development of the other types show ; thus, in 

 the other striped caterpillar, Iphiclides, the stripes grow obsolescent 

 towards maturity, and leave the larva more completely green. Hence, 

 we may trace several lines, to a certain extent parallel, along which 

 the modification of Papilionid larva? has developed, parallel, at 

 least, in that the loss of the juvenile tubercles has been universal, 

 though not always complete, their loss being generally made good 

 by lenticles, and these by spots, and sometimes, by acceleration, a 

 phyletic stage is set further and further back, and finally, perhaps, 

 crowded out. One of these lines, very distinct from the others, is 

 found in Laertias, which has developed in so high a degree that 

 its juvenile bristles, themselves exceptionally simple, are completely 

 lost with the earliest stage ; so, too, are most of the tubercles ; 

 but here a very curious change occurs, those which are lost are 

 replaced in new positions by others entirely different, which take on a 

 more elongated form, and become more properly fleshy filaments, 

 whilst those which remain assume also the new development. The 

 dark and almost uniform colour of the larva throughout life, is to be 

 explained probably by acceleration ; it is the mature colour thrust 

 back into the juvenile stage, to the obliteration of any trace of the 

 saddle which once may have prevailed there, and is in keeping with 

 the present, almost complete, assumption of the mature characters at the 

 second larval stage. In support of this position, may be pointed out 

 the fact that traces of the saddle still exist in the mature forms of 

 other filamentous Papilionid caterpillars allied to Laertias — Ornithoptera, 

 Menelaides, etc. — indicating a still larger development of the same in 

 the earlier stages of the types with which, unfortunately, we are not 

 yet acquainted. In Laertias, then, the saddle has been crowded back 

 out of existence. Another line of nearly as high development we find 

 in Iphiclides, where the extraordinary bristles and tubercles are lost with 

 the very first stage, and maturity marks the second. Here again no 

 saddle appears, the only trace of it left being in the slight deepening of 

 the colour in the new-born larva near the extremities of the body ; here 

 I conceive that the phyletic stage marked by the saddle, and formerly 

 developed in later stages from the incipient contrasts of the first, has 

 been pushed back without invading the first until it is entirely skipped. 

 A third line is represented by the remaining genera, in which the 

 saddle is definitely formed and becomes a marked feature of the earliest 

 stages, to be lost only at a comparatively late period of life, in one 

 instance, Heraclides, not at all. Its loss, however, is effected in two 

 very different methods, as already pointed out, in Papilio and in the other 

 genera, indicating lines along which future strikingly different processes 

 may go on with widely different results — in curious contrast with the 

 somewhat similar results following quite different lines which we see 

 in Iphiclides and Papilio. In Euphocades and Jasoniades we see also 

 the development of special and complicated markings from the simple 

 spots which have replaced the tubercles ; traces of the same may be 

 seen in Heraclides.'" 



As to the value of the bright colours presented by certain of these 

 Papilionid and other larvae, Scudder specially notes (op. cit., p. 860) 



