36 INSECT TKANSFORMATIOXS. 



patches of which may be found on many sorts of 

 leaves during the summer months. 



The immediate origin of colour in the eggs of in- 

 sects is in some cases the enclosed yolk shining through 

 the transparent shell; but in others, the shell is not 

 uniformly transparent, but ringed, banded, or dotted 

 with opacities of various colours. In the eggs of the 

 drinker-moth (Odonestis 'potaloria), for example, there 

 are two circular rings of a green colour, trom the 

 green yolk appearing through the shell; while the 

 rest of the shell is white and opaque, as we have prov- 

 ed by dissection.* Certain ruddy spots on the white 

 eggs of the small rhinocercs beetle ( Onjctcs nasicornis, 

 Illiger) were discovered by Swammerdam to be the 

 red mandibles and spiracles of the unhatched grub 

 seen through the shell; and the v/hite ground, we in- 

 fer, was similarly caused by the body of the grub.f 

 This, however, cannot be the origin of the bright red 

 spots on the beautiful yellow egg of the brimstone 

 moth (Rumia crakcgata^ Duponchel), which may, 

 perhaps, have a similar origin to those of birds. 



With respect to the eggs of birds, it has been re- 

 marked by Mr Knapp,J that in those ' of one hue, 

 the colouring matter resides in the calcareous part ; 

 but where there are markings, these are rather ex- 

 traneous to it than mixed with it. The elegant blue 

 that distinguishes the eggs of the fire-tail {Sylvia 

 phcemcurus, Lath.), and of the hedge-sparrow, 

 ^hough corroded away, is not destroyed by muriatic 

 acid. The blue calcareous coating of the thrush's 

 egg is consumed; but the dark spots, like the 

 markings on the eggs of the yellow-hammer, house- 

 sparrow, magpie, &c, still preserve their stations on 



* J. R. 



t Swammerdani, Book of Nature, i, 13. 

 t Journal of a Naturalist, p. 230. 



