May— July 1SS9.] 



PSYCHE. 



219 



usually a large number on a single leaf. 

 The galls appear late in August but the 

 flies do not emerge until the following 

 summer. Few of these galls were 

 noticed in Michigan, but they are very 

 common about Ames, Iowa. My spec- 

 imens were reared from the leaves of the 

 burr oak, but in a number of instances 

 I have taken galls that seem exactly 

 similar on the leaves of the white oak, 

 ^. alba. 



scutellum was unifoveate. Scutellum 

 broadly rounded behind ; without fovae 

 or grooves ; with a very few hairs ; and 

 with the same scaly appearance as the 

 head and the thorax. Abdomen, shin- 

 ing black in color, with the ovipositor 

 sheathes projecting. Antennae with the 

 first and second joints very stout and 

 sub-equal in length ; third joint longest, 

 and the last four or five joints forming a 

 slight club. The basal joints are sparse- 



Gall-fly : Color, except the tarsi, joints 

 of the legs and antennae, black. Head 

 and thorax shining and with a scaled 

 appearance when viewed with a high 

 power. Thorax almost entirely free 

 from hairs and without parapsidal 

 grooves. The meso-thorax is notched 

 posteriorly making it appear as if the 



ly and the terminal joints rather thickly 

 set with short hairs ; number of joints, 

 13. Eyes coarse ; ocelli rather obscure. 

 Wings, hyaline ; areolet large ; radial 

 nervure reaching the costal margin ; 

 marginal cell open. Length, 1.3 mm. 

 Length of body, i mm. 



