BRITISH INSECTS 



of claspers, twenty in all, and thus differs from a lepi- 

 dopterous insect by having two extra pairs. The adult 

 female has a brownish body, with a dark head, yellowish 

 legs, and black feet. The male is black on the thorax 

 and abdomen. 



We are nearing the end of our story as we reach the 

 Cynipidce, or Gall-Wasps, and, as a familiar example, 

 we may select the species which produces the well- 

 known oak-apple. We can popularly term it the Oak 

 Apple Gall-Wasp, and the insect responsible for the 

 production of this curious formation upon the oak is 

 Biorrhiza pallida. The full story is a fascinating one, 

 and can only be briefly related. It is a story of alterna- 

 tion of generation, that is, a term applied to the breeding 

 of certain insects (such as Gail-Flies and Aphides, for 

 example) when sexual and asexual generations are pro- 

 duced alternately, these generations usually being quite 

 different in appearance and habits. In the case of the 

 Oak Apple Gall- Wasp, one generation appears above 

 ground (resulting in the production of the oak apple), 

 the other occurs upon the roots hidden beneath the soil. 

 The wingless female insect which emerges from the 

 hard round galls upon the roots makes her way above 

 ground early in the year, climbs the bole of the tree, 

 finds the Winter buds, punctures them, and deposits 

 an egg in each incision made. She then dies. In due 

 course the eggs hatch. The producer of these eggs 

 had never been fertilised for, in her generation, there 

 is no male issue, but from the eggs deposited by her, a 

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