ir.] BRIGHTLY COLOURED CATERPILLARS. 51 



gaster lanestris, Odonestis potatoria, Lasiocampa rubi, 

 L. trifolii, and L.roboris. Brown caterpillars, however, 

 unlike black ones, are frequently naked. These fall into 

 two principal categories : firstly, those which, like the 

 Geometridce, put themselves into peculiar and stiff 

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

 closely resemble bits of dry stick ; and, 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 colour is a protection. Red and blue, on the 

 contrary, are much less common colours, 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, would 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 colour than 

 red. Indeed, among our larger larvse, 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 Chcerocampa, 

 which has two bright blue oval patches on the third 

 segment. The species of Gastropacha 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 



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