THE ENTOMOLOGIST. 319 



the earliest by which they were designated. It may, I thinlc, 

 be fairly assumed the law of priority will obtain in these, 

 as in all other instances, when the subject shall be better 

 understood and the synonymy carefully worked out. The 

 economic difference between the groups is that the druids 

 seem to emit no juices deleterious to plants on wliich 

 they feed, but simply separate the two cuticles from each 

 other, consuming the parenchyma contained between them. 

 A fevv only of the ])erfect insects have been obtained, and 

 these appear to have two marginal cells in the fore wings. 

 The euures, on the contrary, emit some fluid, or exercise 

 some power still to be determined, which causes substantial 

 galls distinctly to mark their presence : the fore wings of the 

 perfect insects, so far as hitherto known, have but a single 

 marginal cell. It is probable that every species of tree 

 throughout the world supports at least one of each family, 

 although less than thirty druids and less than a hundred 

 euures at present figure in our scientific lists. In the United 

 States the inquiry has been almost exclusively confined to 

 the willow, and the crop of species that has been reaped is 

 really marvellous. In Britain, alas ! we have ascertained 

 but two, Euura Cynips and E. Gallue, both described by 

 myself more than thirty years ago. Euura Cynips produces 

 the familiar gall to be found almost everywhere on the leaves 

 of the crack willow (Salix fragilis) : this gall is of an oblong 

 form, and protrudes equally from both surfaces of the leaf; 

 it is usually of a red tint on the upper surface, and often has 

 an ornamental appearance. Other species of Salix have 

 their Euura galls, and one of these, discovered by Mr. Lees, 

 is reniarkably beautiful ; it is s))herical and highly coloured, 

 resembling a cranberry. This beautiful object was made 

 known to naturalists in the pages of the 'Entomologist.' 

 Next to the willow, the alder seems most obnoxious to the 

 attacks of a Euura: the parent insect deposits its eggs in a 

 double series on the back of the leaf, one in the axil of each 

 lateral rib, and almost touching the midrib of the leaf: the 

 galls appear in the same situation on the upper side of the 

 leaf, and their appearance, thus regularly arranged, is very 

 striking. 1 know nothing further of its economy : the larva 

 is readily found by cutting open the galls, and its lethargic 

 habits are favourable to the compilation of an accurate lile- 



