NOTES ON NEARCTIC BIBIONID FLIES. By W. L. McAtee, Of the United States Biological Survey. INTRODUCTION. Wishing to identify some Bibionidae and finding no keys available the writer decided to make some. The resulting keys and notes are based largely on the collections of the United States National Mu-seum, and it is hoped that they will be useful to others desiring to study this neglected family. Among Nemocera in general the Bibionidae are distinguished by absence of transverse suture in mesonotum and of discal cell in wing, forking of the radial sector beyond the discal cross vein, and presence of three large ocelli on a well-developed ocellar prominence. Eliminating the flies properly separable as the family Scatopsidae, the Bibionidae may be separated from their nearer relatives with fair satisfaction. From all but the most primitive Mycetophilidae {Paleoplatyura, Apemon, etc.) they are distinguished by possession of two basal cells in the wing; most of them have short and compact (even if many-jointed) antennae, again in contrast to the majority of Mycetophilidae. The latter usuall}'' have all of the tibiae conspicuously spurred, while in the Bibionidae spurs of any magnitude are confined to the front tibiae. The Scatopsidae differ from the Bibionidae in much smaller average size, in possession of but one basal cell, and general reduction in venation. In these characters again they approach the Myceto-philidae, which differ, however, in the elongation of the coxae, and usually of the other leg joints and antennae. In identifying various Bibionidae it is especially desirable, some-times necessary, to have associated sexes of the species. By bear-ing this in mind collectors can greatly help the study of this family. Bibionidae exhibit what is apparently more than a fair share of injuries and malformations which may be connected with emergence from the soil. Distorted tarsal joints are not rare, and in the course of the present study the following more important abnormalities were observed: Bihio femoratus Wiedemann, a female from Plum-mers Island, Maryland, April 30, 1911 (W. L. McAtee), has the left front leg lacking a tarsus, the tibia being only about half the nor-No. 2406— Proceedings U. S. National Museum, Vol. 60, Art. I i. 1
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