The Colours of Animals. 105 



fore, with a very early stage of the Euphorbia Hawk- 

 moth ; there is another species found in South 

 Russia, which has the line, and represents the second 

 stage of the Euphorbia Hawk-moth ; another has 

 the line and the row of spots, and represents, 

 therefore, the third stage ; lastly, there are some 

 which have progressed further, and lost the longi- 

 tudinal line, but they never acquire the second row 

 of spots which characterises the last stage of the 

 Euphorbia Hawk-moth. 



2. Thus, then, the individual life of certain cater- 

 pillars gives us a clue to the history of the species 

 in past ages. 



For such inquiries as this, the larvae of Lepidop- 

 tera are particularly suitable, because they live an 

 exposed life ; because the different species, even of 

 the same genus, often feed on different plants, and 

 are therefore exposed to different conditions ; and 

 last, not least, because we know more about the 

 larvae of the butterflies and moths than about those 

 of any other insects. The larvae of ants all live in the 

 dark ; they are fed by the perfect ants, and being 

 therefore all subject to very similar conditions, are 

 all very much alike. It would puzzle even a good 

 naturalist to determine the species of an ant larva, 

 while, as we all know, the caterpillars of butterflies 

 and moths are as easy to distinguish as the perfect 

 insects ; they differ from one another as much as, 

 sometimes more than, the butterflies and moths 

 themselves. 



