The Colours of A nimals. 89 



cealing themselves on the ground by day, and only 

 coming out in the dark. 



* Yellow and yellowish-green caterpillars are abun- 

 dant, and their colour is a protection. Red and 

 blue, on the contrary, are much less common 

 colours, and are generally present as spots. 



8. Moreover, caterpillars with red lines or spots are 

 generally hairy, and this for the reason given above. 

 Such species, therefore, would be avoided by birds. 

 There are, no doubt, some apparent exceptions. 

 The Swallow-tail Butterfly, for instance, has red 

 spots and still is smooth ; but as it emits a strongly- 

 scented liquid when alarmed, it is probably dis- 

 tasteful to birds. I cannot recall any other case of 

 a British caterpillar which has conspicuous red 

 spots or lines, and yet is smooth. 



9. Blue is, among caterpillars, even a rarer colour 

 than red. Indeed, among our larger larvae, the 

 only cases I can recall are the Lappets, which 

 have two conspicuous blue bands, the Death's- 

 head Moth, which has broad diagonal bands, and 

 two of the Hawk-moths, which have two bright 

 blue oval patches on the third segment. The 

 Lappets are protected by being hairy, but why they 

 have the blue bands I have no idea. It is inte- 

 resting, that both the other species frequent plants 

 which have blue flowers. The peculiar hues of 

 the Death's-head caterpillar, which feeds on the 

 potato, unite so beautifully the brown of the earth, 

 the yellow and green of the leaves, and the blue 



