Neitroterus fumipennis. 23 



mistaken for Neuroterus laeviusculus. Indeed, as I have 

 already said, I myself at the outset confounded laevius- 

 culus \m^h fumipennis. 



Bearing the Fly. The galls are collected when they 

 mature in the beginning of October, and are preserved 

 through the winter in the same way as Neuroterus 

 lenticularis. In one point however they differ essentially; 

 in lenticularis the development of the larva begins and 

 continues without intermission from the time the galls 

 fall to the ground, but in fumipennis on the contrary 

 there is a complete winter rest. If a gall oi fumipennis 

 be opened in the month of March, the larva will be 

 found to be absolutely at the same point of development 

 that it had reached in the autumn; whereas in the 

 other Neuroterus galls the larva is by that time fully 

 grown or has even assumed the pupa-state. It is only 

 during the month of March that larval development 

 begins \x\ fumipennis, towards the end of April it becomes 

 a pupa, and the perfect insect appears in May. But the 

 actual date of its appearance varies from two to three 

 weeks according to the temperature. It is not possible 

 with this species, as with the others, to hasten the 

 development of the larva by keeping the galls in a warm 

 room during the winter months. 



Fly. This fly is easily distinguished from all the 

 other species of Neuroterus, Size, 2 mm. ; thorax dull, 

 black ; base of abdomen orange ; legs, including the 

 femora, orange ; wings, especially at the tips, smoky. 



Experimental breeding. When the fly makes its 

 first appearance in May it finds the oak buds already 

 well developed and beginning to swell, while the scales 



