130 MR. J. WATSON ON THE PLUMULES OR 



this mark of virility may indicate the comparative vigour 

 or age of the insects. On some individuals of the same 

 species they are much more abundant than on others ; and, 

 again, in some species they are plentiful, and in others 

 scarce ; and in some indi\dduals of all species it is difficult 

 to find them at all. On newly caught specimens, however, 

 they are most easily found. 



It is the genus Lycaena, with its neighbour Danis, which 

 affords the scales now submitted to your inspection. The 

 upper-side of the wings of the males is generally bright 

 blue, but at all events with more or less blue irrorations ; 

 the males of certain species, however, are brown. The 

 females are generally brown ; but even when they have blue 

 surfaces I have found no plumules on them, while on the 

 males which have any tinges or reflections of blue these 

 scales are present. No species, however, the males of which 

 are brown, yields these scales ; and yet it is not in these 

 peculiar scales that the pigment or colour-reflection re- 

 sides. To a very eminent lepidopterist I lately wrote, ask- 

 ing if he was aware of any other physiological difference 

 between the blue and brown species. His reply was, " that 

 he could not think there was any other difference, but 

 that it was a most interesting fact that when these males 

 imitate the females in colour they lose another male cha- 

 racteristic." 



Mr. Sidebotham has, with habitual industry and kind- 

 ness, drawn figures of a large number of these scales ; and 

 they are now placed before you. These drawings are as 

 truthful as beautiful ; the slides were mounted from insects 

 in my own cabinet, and I believe reliance may be placed 

 on the correctness of the nomenclature and habitat. These 

 slides and insects are also here for your inspection. 



Nos. I a, 40, 42 a, 46, and 50 belong to the genus Ly carta. 

 Nos. 47, 48, 49, 52, and 53 belong to the genus Danis, ac- 

 cording to the arrangement of Doubleday, Westwood, and 



