SYNOPSIS OF NORTH AMERICAN SYRPHID^. XIX 



at Cambridge I could not discover differences. The genus, as I under- 

 stand it, is based upon the presence of but four visible segments in the 

 abdomen with elongation of the median ones. The types of these spe- 

 cies, however, show the fififi segment to be as well developed as in 

 other species of PipizOj and with no appreciable greater development 

 of the third and fourth segments. 



The genus Nausigaster is a very peculiar one, and has only slight 

 relationship to the other genera, except perhaps Parayus. On account 

 of its general habitus, its punctate markings, and the structure of the 

 abdomen, 1 place it here. 



It may be objected that I place the genus Myiolcpta in this group. 

 Perhaps did I know the European species, I should feel the force of the 

 objection myself, but certainly in the American species the affinity with 

 species of Chilosia cannot be overlooked. Where tlie hind femora are 

 but little thickened, and without spines, there is but little to distinguish 

 them ; even the luleous coloration in the female of some species mimics 

 that in the females of some Chilosicc, and the male facial tubercle re- 

 peats itself in certain Chilosim and Chrysogastrce. 



How Loew could have overlooked the striking relationship between 

 Lepromyia calopus and MyioJepta strigilata I cannot account for. In the 

 latter the third joint of the antenna? is distinctly elongate, the femora 

 are all thickened, with short spines below, and the body is clothed with 

 sparse tomentum, all characters of the genus. The genus thus holds an 

 intermediate i)Osition, connecting Chrysogaster and Myiolepta. 



3IELA^OSTOMI]S^I. 



Small, elongate, thinly pilose species, deep black or shining green, the ab- 

 domen usually slender tcith interrupted hands of bright yellotv, orange, or 

 green ish-yelloio color; face uniformly black, or at least never tc it h light 

 (f round color. Antennce short, face tuberculafe ; neuration Syrphoid ; legs 

 slender. 



a. Wings not longer than the abdomen ; ocellar tubercle large, prominent; abdomen 

 depressed, the lighter markings ferruginous or orange colored. 



PYROPHiENA Schiner. 

 aa. Wings longer than the abdomen ; ocellar tubercle not unusually large; abdomen 

 more slender, the cross- bands yellow or greenish yellow, sometimes shining 

 metallic. 

 h. Front tibite and tarsi of the male dilated, those of the female slightly widened. 



Platychirus St. Fargean and Serville. 

 bb. Front tibiai and tarsi in both sexes slender, not widened.. Melaxostoma Schiner. 



The genus Melanostoma may be taken as the type of this group. The 

 only ultimate difference between this genus, so far as I can discover or 

 define, and Chilosia is iu the absence of entire abdominal cross-bands. 

 On the other hand, the distinction from Syrphus is purely specific. The 

 relationships of Platychirus and Pyrophcena are obvious ; indeed in the 



