150 The Galls of Essex; a Contribution to a 



PoPULus NIGRA, L. Leaf-stallv. The petioles of the leaves 

 are swollen iuto pea-sized, hollow galls, which split when 

 mature, and liberate the aphidious tenants. Pemphigus 

 BURSARius, Hartig. 



PopuLus NIGRA, L. Leaf-stalk. The galls on the petioles 

 are twisted into a spiral form, and are not so thick and 

 discoloured as the above-mentioned species. Pemphigus 

 spiROTHEc^, Koch. 



Conifers. 



Abies communis, L. Bud. The "pine-apple" galls on our 

 common spruce are best known in then* old woody condition, 

 as they remain on the tree for some time after the Aphides 

 have quitted them.. When fresh the gall resembles a small 

 green cone, as it consists of a mass of short, fleshy, ovate, 

 imbricate leaves at the base of a young branch; these enclosed 

 cavities open when the gall is mature, and liberate the 

 Aphides in early summer. Adelges Abietis, Linne. 



Taxus baccata, L. Terminal leaves. At the end of a branch 

 we often find a rosette of crowded and somewhat shortened 

 leaves. The gnat larva lives within the bases of the leaves, 

 and pupates therein in spring ; the gall-gnats emerge from 

 the " artichoke" galls in June. Cecidomyia Taxi, Inchbald. 



Gr amine JE. 



Triticum repens, L. Top shoot. In autumn or winter 

 we find the imbricate, closely-sheathed leaves of a top shoot 

 converted into a more or less cylindrical hard gall, which 

 tapers towards both ends, attaining a length of from one to 

 one and a half inch. In this country one of the parasitic 

 Eurytomidffi (Chalcidid^e) has been given as the gall-maker, 

 which is undoubtedly a Dipteron, and is probably Lonch^ea 

 parvicornis, Meigen. 



