50 OX PLANTS AND INSECTS. [LECT. 



attitudes, so that in form, colour, and position they 

 closely resemble bits of dry stick ; arid, secondly, those 

 which feed on low plants, concealing themselves on the 

 ground by day, and only coming out in the dark. 



Yellow and yellowish-green caterpillars are abundant, 

 and their color is a protection. Eed and blue, on the 

 contrary, are much less common colors, and are gene- 

 rally present as spots. 



Moreover, caterpillars with red lines or spots are gene- 

 rally hairy, and this for the reason given above. Such 

 species, therefore, w r ould be avoided by birds. There are 

 no doubt some apparent exceptions. Papilio machaon, 

 for instance, has red spots and still is smooth ; but as it 

 emits a strongly-scented liquid when alarmed, it is 

 probably distasteful to birds. I cannot recall any other 

 case of a British caterpillar which has conspicuous red 

 spots or lines, and yet is smooth. 



Blue is among caterpillars even a rarer color than 

 red. Indeed, among our larger larvae, the only cases I 

 can recall are the species of Gastropacha, which have 

 two conspicuous blue bands, the Death's-head moth, 

 which has broad diagonal bands, and Charocampa, 

 which has two bright blue oval patches on the third 

 segment. The species of Gastropaclia are protected by 

 being hairy, but why they have the blue bands I have 

 no idea. It is interesting, that the other species both 

 frequent plants which have blue flowers. The peculiar 

 hues of the Death's-head hawk-moth caterpillar, which 

 feeds on the potato, unite so beautifully the brown of the 

 earth, the yellow and green of the leaves, and the b]ue 

 of the flowers, that, in spite of its size, it can scarcely be 

 perceived unless the eye be focussed exactly upon it. 



