SYNOPSIS OF NORTH AMERICAN SYRPHID^. 101 



reddish color on the disk, the yellow band of the second abdominal 

 segment rather broad, and the third and following segments wholly 

 obscurely reddish yellow, except a small circular black spot on the 

 middle of the tifth segment; on two of these are small obscure blackish 

 marks on the third and fourth segments. Three more males from Colo- 

 rado and four from Western Kansas have the black longitudinal and 

 transverse spots very distinct, so that in most of them the yellow is 

 confined to oblique spots nearly as in the typical form. A single fe- 

 male from Colorado, another from Montana, and several from Western 

 Kansas, have the oblique spots of the third and fourth segments coales- 

 cent, leaving only two minute spots in the middle near the front, and 

 on the fifth segment there are a circular median spot and two oblique 

 lateral elongated ones; others, females, have the yellow spots distinct, 

 as in the typical form. 



In several female specimens from Georgia and Florida the abdomen 

 is chiefly black, the first segment nearly wholly so, the second either 

 wholly black or with two small yellow spots, and the yellow triangles 

 of the following segments small and slender; in some the scutellum is 

 distinctly darker above, in one almost blackish on the disk; the speci- 

 men from Montana, however, shows the same blackish color, and here 

 the yellow spots of the abdomen are confluent. A dozen other speci- 

 mens from Georgia and Florida present no essential diflerences from 

 the Western and Northern ones. Specimens from the White Mountains 

 are ])recisely similar to the first-mentioned males from Colorado, and, 

 hence, it is probable that such specimens will usually be found in high 

 altitudes or latitudes. Specimens from Connecticut agree with all the 

 variations i)reviously mentioned; others from Washington Territory and 

 California oiier no peculiarities. 



1 have no doubt from the study of the material here described that 

 pJaniventriH is purely a synonym of marginata. The only point in which 

 it appears to differ from the typical varieties is in the greater amount 

 of yellow on the abdomen, — the black on the third and fourth segments 

 confined to two median spots and a posterior interrupted transverse 

 band dilated at the angles, and the fifth segment with only a single 

 spot. Such specimens occur in Connecticut and Colorado, as well as 

 Florida, whence the species was described. 



One female specimen from Connecticut and two from California, al- 

 though otherwise not differing from the more typical form, have the 

 scutellum a deep shining black, narrowly edged with yellow. There 

 are so many intermediate forms that this character, though a striking 

 one, is not of specific value. 



Two male specimens from Florida (Professor Kiley) have the abdomen 

 wholly reddish yellow, except two small spots on the first segment. I 

 am not sure that they belong to this species. 



