lo Observations on Cynipidae. 



laid on damp sand, but the airiest possible situation 

 must be chosen, to avoid mildew. If the galls are kept 

 in a room, the larvae develop much more quickly than 

 they do in the open air, in consequence of the higher 

 temperature, and in the course of about four weeks 

 they are fully grown. Then if the galls are prevented 

 from shrivelling, by keeping them on damp sand or 

 over water, the first flies may be obtained in about four 

 weeks more. In this way I have hatched flies in 

 November and December, but it was soon apparent 

 that these premature specimens were little fitted for 

 experimental breeding. They were much weaker and 

 more puny than those developed under natural con- 

 ditions, and it is consequently preferable to leave the 

 galls to pass the winter in the open air. This may 

 very simply be done in the following way. Half fill 

 a flower-pot with earth or sand, spread the galls upon 

 this, and cover them over with a layer of moss. Then 

 for greater protection tie a piece of gauze firmly over 

 and plunge the pot up to its rim in the ground. This 

 method of wintering is to be recommended for all galls, 

 as they are thus placed under natural conditions, and it 

 is certain that the development of the flies is left to 

 follow its normal course. In this experiment the flies 

 emerged mostly in April, but a few not until May. For 

 this variation in the time of their appearance I believe 

 that temperature is alone responsible. 



Fly. Size 2-5-3 mm. Colour black; thorax dull, 

 rough and finely punctate; abdomen shining; almost 

 round when looked at from the side, somewhat com- 

 pressed. Legs lighter ; of a brownish red colour, 



