1919] Hine: Geyms Erax 137 



Erax rufibarbis Macquart. 



Male. Total length 16 to 30 millimeters. Mystax and beard 

 distinct reddish yellow, palpi black and clothed with black hair, color 

 of the body dark brown pollinose, thorax with black hair and bristles, 

 scutellum with black hairs on the disc and numerous black bristles, 

 irregularly arranged, on the margin. Legs mostly black with numerous 

 dark and reddish hairs and black bristles, tibia dark reddish on basal 

 half or more, wings brown, many specimens have the margins of the 

 veins more intensely colored, costa not dilated, branching of the third vein 

 nearly opposite the base of the second posterior cell. Abdominal 

 segments six and seven silvery, hypopygium shining black. 



Female colored like the male and just as variable in size; oviduct 

 shining black, about as long as abdominal segments six and seven, 

 abruptly narrowed before the apex, furcate from dorsal view. 



The species has a wide range in Eastern North America, 

 including the West Indies. Normally colored specimens are at 

 hand from as far west as the Dakotas and central Texas. 

 Farther west specimens are lighter in color and indications are 

 that rufibarbis more or less gradually approaches bicaudatus 

 in that region. 



A study of venation in Erax reveals some variations which 

 are useful in grouping species. There is a small group of 

 species that has three submarginal cells normally and there are 

 some species outside this group where now and then a specimen 

 has three submarginal cells in only one or in both wdngs. Thus 

 anomalus, candidus and pernicis may be characterized as a 

 group by the presence of the extra cell while rufibarbis and 

 bicaudatus have an occasional specimen only with this char- 

 acter. An estimate of material at hand indicates that about 

 two per cent of these species are abnormal in this respect. The 

 type of ravus in the U. S. National Museum is an abnormal 

 rifibarbis and from much material studied, results indicate that 

 scarcely any doubt exists that completus is the same, thus adding 

 two more to the long list of synonyms of our common Erax. 



Macquart's figure of the wing of his completus shows the 

 forking on the third vein opposite the cross-vein at the base of 

 the second posterior cell, and not midw'ay betw^een the latter 

 cross-vein, and the small cross-vein as is the case in all the 

 species of Erax having three submarginal cells normally. This 

 fact and his statement regarding the male "Abdomine segmentis 

 duobus apicalibus niveis,'' which is distinctly so in regard to 

 rufibarbis but not of any of the anomalus group, are the con- 



