78 TROPICAL NATURE, AND OTHER ESSAYS. 



hind wings are expanded, a habit found in some of our 

 European species. Mauy of the Lycsenidae, especially 

 the Theclas, have the curious habit, while sitting with 

 their wings erect, of moving the lower pair over each 

 other in opposite directions, giving them the strange 

 appearance of excentrically revolving discs. 



The great majority of butterflies disappear at night, 

 resting concealed amid foliage, or on sticks or trunks, 

 or in such places as harmonise with their colours and 

 markings ; but the gaily-coloured Heliconidse and 

 Danaidse seek no such concealment, but rest at night 

 hanging at the ends of slender twigs or upon fully 

 exposed leaves. Being uneatable they have no enemies 

 and need no concealment. Day-flying moths of bril- 

 liant or conspicuous colours are also comparatively 

 abundant in the tropical forests. Most magnificent of 

 all are the Uranias, whose long-tailed green-and-gold 

 powdered wings resemble those of true swallow-tailed 

 butterflies. Many Agaristidse of the East are hardly 

 inferior in splendour, while hosts of beautiful clear- 

 wings and JEgeriidse add greatly to the insect beauty 

 of the equatorial zone. 



The wonderful examples afl"orded by tropical butter- 

 flies of the phenomena of sexual and local variation, 

 of protective modifications, and of mimicry, have been 

 fully discussed elsewhere. For the study of the laws 

 of variation in all its forms, these beautiful creatures 

 are unsurpassed by any class of animals ; both on 

 account of their great abundance, and the assiduity with 

 which they have been collected and studied. Perhaps 

 no group exhibits the distinctions of species and genera 

 with such precision and distinctness, due, as Mr. Bates 



