42 Galls, Gall-makers, and Cuckoo Flies. [Sess. 



galls on the harebell are caused by C. campanulse. Little 

 purple egg-shaped galls containing the larvae of C. bursariae 

 are found on the leaves of the ground ivy ; when fully devel- 

 oped they fall to the ground, leaving a perforation in the 

 leaf. 



Species of Cecidomyia give rise to galls on the willow, oak, 

 poplar, lime, ash, beech, birch, pine, juniper, hawthorn, and 

 other trees. Their galls are also frequent on many of our 

 common wild flowers, such as the toadflax, buttercup, cuckoo- 

 flower, campion, rock-rose, clover, broom, vetch, rose bramble, 

 ragwort, hawkweed, sorrel, bistort, and bracken. Dipterous 

 galls are exceedingly numerous ; one has only to look for 

 them to find them, since they are borne by a large proportion 

 of our native wild flowers. The species of Cecidomyia are 

 usually named after the plants from which their galls are 

 obtained. 



After the Hymenopterous and Dipterous gall-makers the 

 Aphides, familiarly known as green-fly, are perhaps the most 

 noteworthy. The leaves of the elm and red currant are fre- 

 quently wrinkled or blistered from the presence of these 

 insects ; the young shoots of the fir, larch, and spruce are 

 converted into mimic fir-cones through their agency; knobs 

 or swellings are often seen on the leaf-stalk of the poplar, 

 caused by species of Aphis. In one variety the gall is formed 

 by the spiral twisting of the petiole itself. The Chinese galls 

 of commerce, much valued for the large proportion of tannin 

 they contain, are formed by Aphis Chinensis. Other Aphis 

 galls occur on Juncus, Atriplex, Stellaria, Lonicera, and Cra- 

 taegus. Along with these may be named the galls of the 

 Coccidae or scale-insects. One species of Coccus galls — the 

 Eucalyptus — gives rise to " vegetable coral " ; the males of 

 this species, according to a recent writer, occupy separate galls 

 from the females. A few moths have also to be accredited 

 with the formation of galls. Eetinia makes a cone-like gall 

 on Pinus sylvestris ; Larix, Alnus, Polygonum, and Epilobium 

 are also galled by Lepidoptera. Beetle galls are fairly num- 

 erous : a large round one occurs on the root of the young 

 cabbage. They may be sought for on various species of 

 Brassica, and on Draba, Populus, Scrophularia, Linaria, Veron- 

 ica, and Plantago. 



