THE CANADIAN ENTOMOLOGIST 315 



PARTIAL KEY TO THE GENUS AGROMYZA (DIPTERA). 



FOURTH PAPER. 



BY J. R. MALLOCH, URBANA, ILL. 



The key presented in this paper contains species with the 

 following characters: 



Frons partly reddish or yellow, either the interfrontalia or 

 orbits or both entirely or in part pale; scutellum not noticeably 

 paler than dorsum of thorax; costa extending to apex of fourth 

 vein; halteres whitish or yellowish. 



I believe that the species I described as coloradensis in October^ 

 1913, is the same as that described by Melander, a week or two 

 before the appearance of my paper, under the name genualis. The 

 descriptions agree so clearly that I have indicated the synonymy 

 in the present paper. 



I have included aceris Greene in this key although I cannot 

 tell definitely from the description whether the frons is partly red 

 in front or not. The species is closely related to pruinosa with 

 which it is compared in the key. There are several species closely 

 related to these two, including pruni Grossenbacher, and tvaltoni 

 Malloch, the arbitrary characters used in the keys being responsible 

 for their occurrence in different papers in this series. All of the 

 cambium-mining species I have examined have the orbits poorly 

 or not at all differentiated from the interfrontalia, the thorax with 

 very dense pruinescence, and 4 pairs of dorso-central bristles. 



1. Mesonotum opaque gray; centre of disc between the rows of 



dorsocentrals with a yellowish brown longitudinal vitta 

 which extends on to the disc of scutellum; 4 pairs of dorso- 

 centrals present. Food-plant unknown. N. H.; Mo.; 



III.; N. M.; B. C immacnlata Coquillett. 



Mesonotum shining, or if opaque gray then without a 



Mesonotum shining, or if opaque gray then without a brown 



longitudinal vitta .2 



2. Antennae entirely yellow or reddish, the third joint occasion- 



ally slightly darkened at insertion of the arista 3 



At least the third antenal joint black..,,.. IG 



3. Pleurae most yellow 4 



Pleurae black, at most the sutures yellowish ,, ., 6 



September, 1918 



