ROBBERFLIES OF THE GENUS ERAX.* ■ Jas. S. Hine. The species of this genus are flies of medium to large size. Their larvas, so far as known, Hve in the soil and are predaceous, feeding on various forms of animal life present in such situations. The adults prey on many kinds of insect life, and with other genera of the same family may be considered as having the same relation among insects as hawks among birds. Scopoli proposed Erax as a generic name in 1763 and included under it fourteen species. No genotype was proposed until 1910, when Coquillett designated one of Scopoli's species, barbatus, as the type. As matters stand at the present time all the species which Scopoli placed under Erax are located in other well established genera and the genus in his sense is left without a single representative. In 1838 Macquart used Erax as a generic name. He gave Scopoli credit for the genus, but the characterization he used differs to such an extent that an entirely new group of species was admitted, and some of these have long been known as typical species of Erax. It is evident therefore, that oppor-tunity for change of generic name is presented, but no action is taken because I am satisfied to use Erax in Macquart 's sense and thus obviate the changes which another interpretation would involve. Since no genotype has been named for the genus in Macquart's sense, Erax riifibarbis Macquart is desig-nated as the type of Erax. It is the twenty-second species in Macquart's arrangement in Dipt. Exot., I, 2, 107-119. As an attempt has been made to associate and study all the North American species of the genus it was necessary to pro-cure the loan of much material and to receive aid from various sources. A generous response has made it possible for me to do much more than could have been accomplished otherwise, and my appreciation is most cordially extended to the following institutions and students for services rendered : Kansas University, Academy of Natural Sciences, National Museum, Carnegie Museum, Museum of Comparative Zoology, American Museum of Natural History, Biological Survey, Charles W. Johnson, J. M. Aldrich, Frederick Knab, Nathan *Contribution from the Department of Zoology and Entomology, Ohio State Universit3\ No. 57. 103
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