104 ANIMAL COLORATION. 



have longitudinal stripes; for instance Notodonta chaoma, 

 N. dodoncea upon oak, Ptilophora plumigem, which feeds upon 

 oak and poplar; Lophopteryx carmdita, which feeds upon 

 birch. Acronycta megacephala and liyustri are also striped, 

 and so is the genus Cymatophora. Curiously enough, most of 

 these larva? are day feeders, and so their coloration is less 

 useful still. It has been urged that stripes are useful in 

 breaking up the large area of a caterpillar's body, and so 

 rendering it less conspicuous than it would be if all of one 

 colour. But on an oak leaf a different method would be more 

 advantageous, one might suppose. The longitudinal striping 

 is very suggestive in these cases of some more deep-seated cause 

 of coloration. We must therefore conclude, after considering 

 the examples brought forward in the last pages, that the 

 longitudinal striping of caterpillars is a phenomenon the 

 explanation of which must be still regarded as sub judice. 

 There are many facts which favour the view that it is to 

 be explained on the very simple hypothesis of a need for 

 resemblance to the environment; but there are other facts 

 which do not altogether suit this hypothesis. 



The Resemblance of the Larvae of Geometers to Twigs. 

 A very large percentage of lepidopterous caterpillars are 

 green ; the colour is due not only to the contents of the ali- 

 mentary canal, but also to the presence of a pigment known as 

 metachlorophyll in the blood ; metachlorophyll is a slightly 

 altered derivative of the chlorophyll of the food plant. Where 

 the integument is but little pigmented, the caterpillar under 

 these circumstances appears green. If more pigment is present 

 it is brown. In other cases the integumeutal pigment is so 

 abundant and varied as to entirely conceal the green colour. 

 The colour alone, apart altogether from the form of the cater- 



