118 The Galls of Essex; a Contrihution to a 



British species are known to produce galls, and many of these 

 are amongst our most familiar ones, — e. <j., the dewberry-stem 

 gall, the willow rose-gall, the beautiful little purse-like gall 

 on the leaves of the meadow-sweet, the ground-ivy leaf-gall, 

 the shining yellow and red nodules on the stems of the bed- 

 straw, &c. ; but as I have lately given a synopsis of the 

 British species in the 'Entomologist,'^ 1 must refer the 

 reader to that paper for information respecting such species 

 as have not yet been found in our county. Most of the galls 

 made by the Cecidomyid^e are especially noticeable, and, as 

 I have said, many are quite familiar to us ; still the gall- 

 gnats themselves are very small, obscure, and easily over- 

 looked by the general naturalist, although a specialist writes 

 of them, "these flies (Cecidomyidae) are the most elegant 

 and delicate little creatures in the whole of the Diptera." 

 Their life-history is very varied, and as the nature of their 

 metamorphosis is of consequence when breeding the flies, so 

 that the student may know whether they pupate in the gall 

 or otherwise, I have noticed this in the table of species. 



Another family of the great order Diptera — the Trypetidse, 

 whose economy is so especially interesting to the phytologic 

 entomologist — includes a few gall-makers, besides numerous 

 leaf-miners, leaf-blotchers, flower-feeders and fruit-feeders. 

 The bright-coloured, spotted and banded winged, flies are 

 objects of especial beauty, and are easy of specific arrange- 

 ment. The galls produced by them nearly all occur in the 

 seed-capsules and flower-heads of various Compositae, and are 

 therefore not very noticeable, but the well-known thistle-stem 

 gall of Urophora Cardui is an exception. The Trypetidae 

 pupate within the galls. Two or three other fly-galls are 

 known, but they call for no especial remarks, except their 

 diversity of habits from their congeners, so we will pass on 

 to the Aphis galls, about which I must also be very brief, 

 although they really deserve a separate paper. The pine- 

 apple-like fir galls and elm and poplar leaf-galls are familiar 

 examples of their productions, but then- economy is especially 

 involved and obscure. The interesting biological questions 



*^ ' Entomologist ' xiii. 146—154 (July, 1880). 



