346 Studies in the Theory of Descent. 



red when the caterpillars are feeding, do not 

 completely ripen till the autumn, when the leaves 

 are shed, and the yellowish-red clusters of berries 

 can be seen at a distance. The caterpillar, how- 

 ever, pupates long before this time. 



I have considered this case in such detail be- 

 cause it appears to me of special importance. It 

 is the only instance which teaches us that the rows 

 of ring-spots of the Deilephila larvae proceed from 

 one original pair the only instance which permits 

 of the whole course of development being traced 

 to its origin. Were it possible to arrive at the 

 causes of the formation of these spots, their 

 original or primary significance would thereby be 

 made clear. 



I will now briefly summarise the results of the 

 investigation of the biological value of the Deile- 

 phila ring-spots. 



In the known species of the genus now existing 

 these spots have different meanings. 



In some species (certainly in Galii, and pro- 

 bably in Euphorbia and Mauritanica) the con- 

 spicuous ring-spots serve as signals of distasteful- 

 ness for certain enemies (not for all). 



In a second group of species they serve as a 

 means of alarm, like the eye-spots of the Chczro- 

 campa larvae (Niccea ? light form of GaliiT). 



Finally, in a third group, of which I can at 

 present only cite Hippophaes, they act as an 

 adaptive resemblance to a portion of a plant, 



