284 OAK GALLS AND GALL INSECTS 



to escape and the necessary investigations can be carried on 

 without difficulty. As the oak does not usually bear fruit until 

 it is about twenty years old (though it depends to a large extent 

 upon soil and climate), this method is obviously useless in the 

 cases of those species which produces galls on the catkins. For 

 these the only way is to experiment upon the full grown tree by 

 covering in certain branches with gauzs. When the act of 

 oviposition is witnessed the bud or leaf should be marked by 

 tying just beneath it round the branch, a piece of cotton or wool. 

 It is necessary with those galls which fall to the ground to 

 mature (such 3.s N euvoterus lenticulavis) that the natural temperature 

 and amount of moisture should be maintained. As before men- 

 tioned, in order to prevent any mistakes, it is desirable that verv 

 careful and accurate observations should be made. It is always 

 best when possible that a series of different experiments with the 

 same species should be carried on at the same time. Where 

 one experiment fails another may be successful, and time, 

 saved. Even then many disappointments are sure to occurs 

 The result of one apparently successful experiment in breeding 

 should not be taken as proof, but to allow for possible error 

 the observation should be repeated the following year. There is a 

 great deal yet to be found out with regard to alternation of 

 generations among these remarkable insects, and in the case 

 of such species as Andi'icus solitavius the life-history has yet to be 

 worked out. 



Pi'csevvation of Galls. 

 With regard to the preservation of galls for a collection. 

 There are many kinds which are very difficult to preserve as 

 they lose their colour and shrink ; and this especially applies 

 in the case of such galls as Andvicus radicis which contain a 

 great amount of moisture, causing the gall to shrivel and wrinkle 

 after evaporation. I have tried the quick drying method with 

 only partial success, and in many instances by gradual drying 

 and by not exposing the galls to any very high temperature I 

 have caused them to keep their shape and colour fairly well ; 

 but such galls as Nenrotevus li'icolor and N . baccarum soon lose 

 both. If kept in spirit the proper form is retained but the colour 

 as a rule gradually vanishes. I find that the best thing to do 

 is to make coloured drawings of the galls when fresh, so that a 

 fair idea of their natural appearance may be had, after the 

 galls themselves have lost their proper shape and colour. 



