18 INSECT TRANSFORMATIONS. 



but the down upon the eggs of insects does not con- 

 duce to this end. Whether insect eggs be naked or 

 clothed with down, they are invariably, as far as their 

 history has been investigated, deposited close to or 

 upon substances capable of affording food to the young 

 when hatched. In making experiments upon the spe- 

 cific gravity of eggs, it should be remembered that 

 no infertile or unimpregnated egg will sink; for having 

 some hundreds of these laid by different species of 

 insects reared in our cabinet, we found, upon trial, 

 that they uniformly floated, while those which we knew 

 to be impregnated as uniformly sunk. A female, for 

 example, of the rose-leaf roller [Lozoicema Rosanctj 

 Stephens) was reared by us, in solitude, under an 

 inverted wine-glass, upon the side of which she glued 

 a patch of eggs, of course, unimpregnated: these, 

 upon trial, all floated in water. But eggs of the same 

 species taken from the outside of a pane of glass 

 close to a rose-tree, all sunk in water; and it is to be 

 fairly presumed, as the parent of the latter was in a 

 state of freedom, that these were impregnated. We 

 found the same distinction, indeed, to hold in the eggs 

 of the drinker moth, the gypsey moth, and numerous 

 other insects.* 



Dr Good's account of ' honey-dew,' which he des- 

 cribes as ' a pecuhar haze or mist loaded with a poi- 

 sonous miasm,' that stimulates ' the leaves of the hop 

 to the morbid secretion of a saccharine and viscid 

 juice' — appears to us unsupported by facts. Lin- 

 naeus,! on the contrary, who was not wedded to the 

 meteorological theory of a miasmatous haze, ascribes 

 the honey-dew on the hop leaves to the caterpillar of 

 the ghost moth [Hepiahis hmmdi) attacking the roots. 

 Dr Withering, favouring this account, recommends 

 covering the roots with stones as a preventive; for 



* J. R. t Quoted by Keith, Phys. Bot. ii, 143. 



