GALL-WASPS. 359 



gall-wasp (Cynips kollari, Hart.), which sometimes occurs in 

 large numbers on young oak plants. The galls* may be cut off 

 with a knife while they are still young and soft, and if thrown 

 away they dry and shrivel, and the maggots within perish. 

 Titmice are very useful in oak nurseries, as they pick the 

 maggots out of the galls. 



It is interesting to know that in many species of gall-flies, 

 a wingless, hibernating, parthenogenetic generation always 

 alternates with a winged generation of both sexes. As an 

 example, the wingless agamic female form, Cynips aptera, is 

 hatched from galls on the roots of the oak, and hibernates in 

 the soil, laying in the spring, on the terminal buds of the 

 oak, a number of unfertilised eggs. These cause galls on the 

 terminal shoots from which the winged forms of both sexes, 

 C. terminalis, Fabr., develop. The fertilised ? of this insect 

 lays her eggs on the roots of the oak, and from them C. aptera 

 is hatched out, and so forth, t 



2. Secondary Gall-Wasps. 



These are also termed Inquilines, or fellow -lodgers, as their 

 ? lay eggs in galls made by the true gall-flies, and their larvae 

 are either parasitic on the larvae of the latter, or else merely 

 live with them in the same gall, e.g., Synergus vulgaris, Htg., 

 lives in galls of Cynips folii, L. 



3. Parasitic Gall-wasps. 



The ? lay their eggs in other insects in which their larvae 

 are parasitic, and thus form a connecting link with the 

 Iclineumonidae, e.g., Allotria erythrocephala,~H.tg. 



Parasitic on the Rose aphis. 



Hess gives a summary account of the chief species of 

 gall-wasps. 



* Miss Ormerod, op. cit., p. 237. 



f Many so-called galls, or malformations of plants, are caused by fungi or 

 bacteria as well as by gall- wasps and gall-flies. A beautifully illustrated book 

 on "British Vegetable Galls," by E. T. Connold, was published in 1901, by 

 Hutchinson & Co., Paternoster Row, London, and the author is now preparing 

 for the press a second volume, on oak-galls only. 



