454 Studies in the Ttieory of Descent. 



This is especially striking in the genus Deilephila, 

 eight species of which are allied in the imaginal 

 state in a remarkable degree, whilst the larvae 

 differ greatly from one another in colour, and to 

 as great an extent in marking. These eight 

 species are D. Nicaa, Euphorbia, Dahlii, Galii y 

 Livornicdy Lineata, Zygophylli, and Hippophdes. 

 Of these, Nicaa, Euphorbia, Dahlii, Zygophylli, 

 and Hippophdes are so much alike in their whole 

 structure, in the form of the wings, and in mark- 

 ing, that few entomologists can correctly identify 

 them off-hand without comparison. The larvae 

 of these four species, however, are of very different 

 appearances. Those of Euphorbia and Dahlii 

 are most alike, both being distinguished by the 

 possession of a double row of large ring-spots. 

 Zygophylli($&& Fig. 50, PI. VI.) possesses only faint 

 indications of ring-spots on a white subdorsal line ; 

 and in Hippophaes there is only an orange-red 

 spot on the eleventh segment, the entire marking 

 consisting of a subdorsal line on which, in some 

 individuals, there are situated more or less de- 

 veloped ring-spots (see Figs. 59 and 60, PI. VII). 

 If we only compare the larvae and imagines of D. 

 Euphorbia and Hippophaes^ we cannot but be 

 struck with astonishment at the great difference of 

 form-relationship in the two stages of development. 

 In the case of D. Euphorbia and Nicaa this 

 difference is almost greater. Whilst these larvae 

 show great differences in colour, marking, and in 



