COLOUR IN SPECIES. 279 



species of vultures, hawks, gulls, and a few others, the 

 adult plumage is not put on until after two, three, or 

 even four years. Humming-birds, and nearly all their 

 splendid coloured congeners, during the first year, are 

 devoid of those richly coloured plumes which they ac- 

 quire in the second. These instances are sufficient to 

 set the young ornithologist upon his guard ; and yet, in 

 mature life, the colours of birds are their best and most 

 obvious distinctions. Among insects, also, they afford 

 considerable help, especially in the Lepidoptera ; where 

 the ground tint and the pattern are almost invariable 

 in the individuals of one species, although there may be 

 some trifling variation in the latter. The ocellated 

 spots, for instance, in our well known meadow but- 

 terflies, forming the groups of Hipparchia and Pohjom- 

 metus, will frequently vary as to their size and number, 

 although the pattern of the wings wiU be, in other re- 

 spects, precisely the same. In this order, the colours 

 of the sexes are rarely different ; although there are some 

 remarkable exceptions to this rule among the exotic 

 diurnal tribes. In the. Hymenoptern, ako, the same 

 species of bee will appear very different upon first 

 emerging from the pupa, and when his short career is 

 drawing to a close : the delicately coloured hairs, with 

 which his body was at first defended, will be partly 

 worn off'; and the dark colour of the abdomen, appearing 

 beneath, will give the whole insect a different aspect to 

 that which it had in youth. Let the young entomologist, 

 if he wish to ascertain this fact, capture some of those 

 species he will find on the wing at the end of July, 

 and then renew his captures, in the same locality, in 

 the month of September ; in all probability he will meet 

 with the same species, but apparently clothed in dif- 

 ferent hues. Colours, in the neuropterous order, are 

 very evanescent. Those which ornament the bodies of 

 the dragon flies, not only fade after death, but vary in 

 individuals of the same sex : the beautiful green, so 

 prevalent among the locusts, generally changes, in the 

 preserved specimen, to a light brown : the under wings, 



T 4 



