102 INVERTEBEATE ANIMALS. 



Group 239.— Divisions TEREBRANTIA and ACULEATA 

 in part. Saw-flies, Tenthredince ; Gall-flies, (7/ynipici<2; 

 Ichneumons, Wasps, Hornets, &c. 



More than 250 kinds of galls have been described, 

 many of which are formed by Cynipidcs on 

 the roots, twigs, or leaves of the oak. The 

 minute particle of virus injected by the insect 

 when depositing its egg seems to possess 

 properties capable of compelling the growth- 

 force of the oak to develop cells constructing 

 an oak-apple, a nut-gall, a leaf-spangle, or 

 some other form of nidus best adapted to the 

 habits and necessities of the tiny parasite : a 

 correlation truly wondrous. Galls are known 

 to be injurious to oak-trees ; can their pre- 

 sence be associated with some compensative 

 advantage ? 

 Note the enormous length of the ovipositor and 

 sheath in Pimpla atrata. British series, chiefly 

 local, deposited by the Royal Institution, 

 Liverpool. 



Upper Compartment. 

 Nests of Social Wasps ; Galls and Oak-apples, with 

 the Gall-fly Cynips, together with specimens 

 of Allantus and Chalcis, from the same gall. 



Group 240.— Family FORMICID.E and Division MELLI- 

 FERA. Ants and Bees. About 180 British species of 

 Bees have been described. 



Mr. Belt's work on Nicaragua contains a large 

 amount of very interesting information on the 

 habits of ants, especially those of a species of 

 stinging ant which finds both food and a home 



