442 



INTRODUCTION TO ZOOLOGY chap, xxvii 



OAK GALLS (continued) 



Some of the Cynipidae do not form galls them- 

 ^ii^GaUs^^ selves, 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 virall, several small cavities, 

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



