INTRODUCTION 
Tue beautiful colours, diversity of sizes, and the 
peculiar shapes of many British oak galls impart an 
unusual interest and charm to their study. It, how- 
ever, possesses an additional interest to the student of 
Natural History. The gall-makers, with the numerous 
Parasites, Inquilines, and other creatures which 
emerge from the galls, invite the student to extend 
his research in another direction, and when he does 
so Entomology becomes inseparably associated with 
Botany. 
Collecting oak galls is a most fascinating occupation. 
It does not require a greater amount of time than is 
devoted to gathering material for an herbarium. 
The principal British oak gall-producing insects are 
the Cynipide, a family of the Hymenoptera. Flies 
with two wings, or Diptera, are represented by a few 
species; there is also one species of Coccus, and one 
Fungus. 
A few species of flies producing galls on other 
plants, are of medium size. Tephritis bardane, and 
Urophora solstitialis, which produce galls in the seed- 
heads of common burdock, and in thistle stems 
respectively, are typical examples. The alar extent 
of these species is about 8-10 mm. But the majority 
of gall-flies (including those on the oak) are very 
diminutive, many species not measuring 2mm. To 
these the name of gall-enats, or gall-midges, may 
appropriately be given. They produce galls in a great 
