Insect Colouring 



the black parts reveal nothing out of the 

 common. The black is homogeneous and 

 everywhere of equal depth. On the other 

 hand, in the coloured portions, we see little 

 polygonal, granular masses, forming a close- 

 meshed network. By cutting round the cir- 

 cumference of the abdomen with a pair of 

 scissors, the horny integument of the dorsal 

 surface may readily be removed in one piece, 

 without any shreds of the organs which it 

 protected. This large strip of skin is trans- 

 parent in the zones that correspond with the 

 white bands in the natural state; it is black 

 or yellow on the black or yellow bands. 

 These last indeed owe their colouring to a 

 layer of pigment which the point of a paint- 

 brush will easily loosen and remove. 



As for the white bands, their origin is this : 

 once the skin has been removed, the dorsal 

 surface of the abdomen, whose graceful mo- 

 saic is not in any way disturbed, reveals a 

 layer of polygonal white spots, distributed in 

 belts, here densely and there less so. The 

 denser belts correspond with the white bands. 

 It is their magnificent opaque white granula- 

 tions which, seen through the transparent 

 skin, form the snow-white stripes in the live 

 Spider. 



Treated with nitric acid on the microscopic 

 285 



