278 OAK GALLS AND GALL INSECTS 



as the cambium ring is only represented by a thin layer at the 

 base of the bud ; consequently in many cases no gall is formed 

 because the eggs have not been placed exactly in this growing 

 zone. The cell growth after the emergence of the larva is some- 

 times very rapid, in some cases it commences before the larva 

 is quite free from the egg. In the case of Tvigonaspis remim a 

 period of months elapses after the egg has been laid before gall 

 formation commences. The probable cause of the differences in 

 size and form, etc., existing between various galls has already 

 been referred to, but besides having some property in their saliva 

 which acts on the surrounding tissue, the different ways in 

 which the larvae feed may also have some important bearing on 

 the case. 



The gcneval chavacteristics of the Family Criiipidae. 



Antennae twelve to fifteen jointed, never elbowed. 



Legs have the trochanters biarticulate. 



Wings without a stigma. One radial cellule. One to three 

 cubital cellules. Submarginal nervure absent. 



Prothorax reaching at the sides to the insertion of the wings. 



Abdomen pedunculated and compressed. 



No cocoon spun by the larvae, which are apodal. 



Eggs stalked. 



The Cynipidae are divided into five Sub-Families : — 



(i.) The Ibalina, containing a single genus Ihalia including 

 one species, which is parasitic on Sirex. 



(2.) Allotrina, containing two genera, Phaenoglyphis and 

 Allotria, parasitic on Aphides or on the parasites of Aphides. 



(3.) Encoelina, containing genera which include species 

 parasitic on larvae of various insects, especially Diptera, such 

 as Musca, Evistalis, Tachina, etc. 



(4.) Figitina. This sub-family is divided into three 

 sections, Anacharides, Onychides and Figitides. The Onychides 

 are chiefly parasitic on Beetle and Syrphns lar\'ae, while the 

 Figitides comprises genera (such as Figites) which contain species 

 parasitic chiefly upon Diptera, mostly dung-flies of the family 

 Sarcophagidae. 



I have mentioned the above sub-families of the Cynipidae 

 merely to show how very generally parasitic the members of the 



