Neuroferus-Spathegaster Group. 131 



ovipositor fitted for piercing buds ; and if on the other 

 hand the following generation appears at a season 

 when both buds and leaves are found, a perfectly 

 different form of ovipositor will be necessary for 

 piercing the latter. An accurate knowledge of the 

 ovipositor is of importance in investigating the history 

 of those species of gall-flies whose alternate generation 

 is not yet known. For instance, if a fly is reared from 

 a leaf-gall, and is furnished with an ovipositor which 

 is not adapted for piercing leaves, it may be inferred 

 with certainty that another generation, capable of pro- 

 ducing leaf-galls, belongs to this fly. 



It will be found of interest, therefore, to review the 

 various forms of ovipositor described. 



I. Neuroterus-Spathegaster Group. 



A glance at the illustrations ^ of the two ovipositors 

 will enable us to appreciate their great difference. In 

 Neuroterus laeviusculiis (Fig. 2) the ovipositor is very 

 long and spirally coiled ; in Spathegastcr albipes, on 

 the contrary (Fig. 2^), it is short and slightly curved. 

 The other species of Neuroterus show a somewhat 

 shorter ovipositor, especially Neuroterus fumipennis 

 (Fig. 3). Spathegaster ovipositors do not vary. The 

 Neuroterus ovipositor has a hook-shaped point, and 

 can therefore never penetrate perpendicularly into a 

 bud. The Spathegaster ovipositor, being only slightly 

 curved, can pierce vertically the surface of the leaf. 



^ I may here remark that the illustrations are all drawn from 

 photographs, and therefore give exact relative proportions. The draw- 

 ings of the eggs near them are also photographed on the same scale. 



K 2 



