442 



INTRODUCTION TO ZOOLOGY CHAP, xxvn 



OAK GALLS (continued') 



Some of the Cynipidae do not form galls them- 

 Se ^ ves 5 but lay their eggs in a developing gall 

 formed by a true Gall Wasp. We often find, 

 therefore, the central cavity in the gall inhabited by the gall- 

 maker, and around this, in the wall, several small cavities, 

 occupied by the " guest-wasps " or Inquilines. This is the 



