W. M. DAVIDSON 35 



NOTES ON CERTAIN SPECIES OF MELANOSTOMA 



(DIPTERA; SYRPHIDAEj' 



BY W. M. DAVIDSON 



U. S. Bureau of Entomology, Vienna, Va. 



The following paper is an attempt to deal with the commonei 

 North American species of Melanostoma wherein the facial 

 ground color is obscured by whitish pollen, more or less in rii)ple- 

 like formation, and the abdomen is banded with metallic fasciae. 



The writer has placed Bigot's M. rostratum as a variety of the 

 common obscurum Say of the Eastern States. From the de- 

 scription M. pictipes Bigot is not with certainty applicable to 

 any species known to him. 



Three of the species, stegnum Say, obscurum Say var. rodralain 

 and chaetopoda new species were bred from the ovum, the larvae 

 feeding on aphids and transforming much in the same manner 

 as contemporaneous larvae of species known to Ije normally 

 aphidophagous (Eupeodes valuer is Osten Sacken, Allograpta 

 obliqua Say, etc.). Whether or not Melanostotna larvae are nor- 

 mally aphidophagous appears still in doubt; it is certain that 

 field collections of larvae associated with aphids are very rare, 

 when the abundance of the adult flies is taken into consideration. 



In the laboratory, however, the larvae are easily reared on an 

 aphid diet, while gravid females, collected in the field, deposit 

 ova in cages about as readily as species of Syrphus, Eupeodes or 

 Allograpta. 



Acknowledgment is due to IVIr. C. Howard Curran, Vineland, 

 Ontario, for the type material of Melanostoma Ontario new species 

 for other material used in the preparation of this paper, and also 

 for helpful suggestions. 



Melanostoma chaetopoda new species (Text-fig. A.) 



Male. Antennae oval, third joint twice as long as wide; brownish black, 

 lighter below; arista black. Vertex and frontal triang'e shining bluish-ljlac-k; 

 pile black, of moderate length. Face with whitish punctate pollen, a median 

 shining black stripe not reaching the antennae, facial pile white; breadth 



' Published with the permission of the Secretary cf Agriculture. 



TRANS. AM. ENT. SOC, XLVIII. 



