3 1 6 Studies in the Theory of Descent. 



opposed to the theory ; but light lateral stripes, such 

 for example, as those possessed by Gonepteryx 

 Rhamni, can never be disadvantageous, and may 

 be of use, even on large leaves, so that if we 

 consider them as an inherited character, there is 

 no reason for natural selection to eliminate them. 

 In the case of caterpillars living on vetch, clover, 

 and other Leguminosce, it must not be forgotten 

 that, although their food-plants do not present any 

 longitudinal arrangement of parts, they always 

 grow among grasses, the species feeding on such 

 plants always resting between grass stems, and 

 very frequently on the grass itself, so that they 

 can have no better protective marking than 

 longitudinal stripes. The striping of the Hesperidce 

 larvae, which partly feed on grasses but mostly on 

 species of Leguminosa y can be explained in a 

 similar manner. 



It is not here my intention to go through all 

 the groups of Lepidoptera in this manner. The 

 instances adduced are quite sufficient to prove 

 that longitudinal stripes occur wherever we should 

 expect to find them, and that they really possess 

 the biological significance which I have ascribed to 

 them. That these markings are occasionally con- 

 verted into an adaptive imitation of certain special 

 parts of a plant, is shown by the larvae of many 

 moths, such for example as Chesias Spartiata, 

 which lives on broom (Spartium Scoparium), 



