ii.] PREHISTORIC CATERPILLARS. 61 



protected by their curious resemblance to spotted snakes. 

 One of the large Indian species has even acquired the 

 power of hissing. 



Moreover, as Weismann points out, we may learn 

 another very interesting lesson from these caterpillars. 

 They leave the egg, as we have seen, a plain green, like 

 so many other caterpillars, and gradually acquire a 

 succession of markings, the utility of which I have 

 just attempted to explain. The young larva, in fact, 

 represents an old form, and the species, in the lapse of 

 ages, has gone through the stage which each individual 

 now passes through in a few weeks. Thus the cater- 

 pillar of Chcerocampa porcellus, the small elephant 

 hawk-moth, a species very nearly allied to Ch. elpenor, 

 passes through almost exactly the same stages as that of 

 Ch. elpenor. But it leaves the egg with a subdorsal 

 line, which the caterpillar of Ch. elpenor does not 

 acquire until after its first moult. No one can doubt, 

 however, that there was a time when the new-born 

 caterpillars of Ch. porcellus were plain green, like those 

 of Ch. elpenor. In this respect, then, Ch. porcellus is a 

 newer specific form than Ch. elpenor. Again, if we 

 compare the mature caterpillars of Chcerocampa, we 

 shall find there are some forms, such as Ch. myron and 

 Ch. chcerilus, which never develop eye-spots, but which, 

 even when full grown, correspond to the second stage of 

 Ch. elpenor. Here, then, we seem to have a species still 

 in the stage which Ch. elpenor must have passed through 

 long ago. 



The genus Deilephila, of which we have in England 

 three species the euphorbia hawk-moth, the galium 

 hawk-moth, and the rayed hawk-moth is also very 



