SYNOPSIS OF NORTH AMERICAN SYRPHID^. 281 



GEOLOGICAL DISTRIBUTION. 



Through the courtesy of Mr. Scudder, I was enabled to examine his 

 collection of specimens, and the drawings for his forthcoming work on 

 fossil insects, in this family. The specimens are, many of them, in a 

 truly remarkable state of preservation, admitting frequently of definite 

 and decided opinions as to their relations. Of the thirty or more spe- 

 cies which Mr. Scudder had separated out, I was first struck with the 

 fact that probably all belong to the first division of the family with a 

 basal cross- vein, a conclusion at which Mr. Scudder had already, inde- 

 pendently, arrived. There are two possible exceptions, bat both, iu 

 view of the general relations of the other specimens, doubtful. The 

 first was the specimen which Mr. Scudder had doubtfully referred to 

 Eristalis (Bull. U. S. Geol. Surv., iii, 750). As regards this, however, 1 

 think that the problematic determination is not the correct one. The 

 other sj^ecimen — named Milesia quadrata (Bull. U. S. Geol. Surv., iv, 

 752) — I would, contrary to the opinion first held by me, remove from 

 this group. The neuration is, iu large i^art, conjectural, and iu all 

 probability has, as Mr. Scudder described, a basal cross- vein, removing 

 it from Milesia and its congeners. The species is unusually large for a 

 JSyrphus, but yet its afiSnities are evidently with that genus. 



The next most striking point observed was the predominance of the 

 Syrphus forms. TJie large number of the sj)ecies, as well as specimens, 

 belong to this genus in apparently a narrow sense, and many of them 

 are peculiarly characteristic. Singiilarlj^, all of them appeared to have 

 the abdominal cross-bands interrupted or emarginated. Iu none did I 

 find entire bands as in S. rihesli or LesueuriL Not a few had the pic- 

 ture very like that of Didea laxa. The neuration in all showed much 

 uniformity. The anterior cross-vein is basal and only rarely with any 

 marked degree of obliquity. In the larger number the third vein is 

 straight, or anteriorly convex, but occasionally gently sinuous, as in 

 Catatomba ijyrastri., for instance. A very noticeable tendency was ob- 

 served iu the termination of the third vein near or beyond the tip of the 

 wing, as iu Rhingia and some species of Chilosia. 



(Jhrysof/aftter was identified with considerable certainty in specimen 

 No. 12021. The profile of the head, moderately elongate antennae, size, 

 metallic coloration, apparent puuctulatiou, and what seemed evidently 

 rugose markings on the front, are all strongly characteristic. The neu- 

 ration is, however, more like that of tSyrj)](US or Chilosia than that of 

 the typical Chrysoqaster; nevertheless I should feel little hesitancy in 

 placing the species in the genus in the sense accepted for our American 

 species. Another species (specimen No. 5102) is very characteristic of 

 Sphegina, although the structure of the head could not be made out. 

 The size, thickened hind femora, provided with spines below, and the 

 elongate spatulate shape of the abdomen, were especially striking. The 

 neuration, so far as could be made out, is SpheginaUke. 



