32 PSYCHE [April 
NOTES ON THE SYNONYMY OF THE SPECIES OF ERAX OF THE 
EASTERN UNITED STATES. 
BY CHARLES W. JOHNSON, BOSTON, MASS. 
In most catalogues of insects there are some names in use which we know should 
be changed. This fact is brought forcibly to our minds in preparing faunal lists, 
and that such names should no longer be used is evident; a faunal list, however, is no 
place for such changes, which often require some elucidation. ‘That the present 
names in use for the common species of the genus Erax are misapplied, is evident 
to all systematic dipterologists. Working on three faunal lists has compelled me to 
take up this matter, for it does not seem desirable to continue to perpetuate these 
discrepancies. While the following synonymy has been largely intimated by Baron 
Osten Sacken, and Dr. Williston, authors have failed to realize its significance. 
ERAX AESTUANS (Linné). 
Asilus aestuans Linné, Syst. Nat., 12 ed. 1007, 1767. 
Dasypogon aestuans Fabr., Syst. Antl. p. 164, 1805. 
Asilus macrolabis Wied., Auss. Zw. Ins., I, 458, 1828. 
Asilus aestuans Macq., Hist. Nat. Dipt., I, 312, 1834. 
Erax femoratus Macq., Dipt. Exot., I pt. 2, p. 115, 1839 (c"). 
Erax incisuralis Macq., Dipt. Exot., I, pt. 2, p. 117, 1839 (2). 
Evrax bastardt Macq., Dipt. Exot., I, pt. 2, p. 117, pl. 9, f. 7, 1839 (%* 2). 
Erax tibialis Macq., Dipt. Exot., I, pt. 2, p. 118, 1839 9. 
‘This is the most common and variable of the eastern species of Erax. It is on 
the other hand the only one with three white abdominal segments, therefore, it seems 
that the brief description of Linné can only apply to this species: “cinereus abdominis 
ultimis tribus segmentis albis. Habitat Pennsylvania.” The number of white 
segments, however, varies from three to four, the latter representing the A. macrolabis 
of Wiedemann. If this was constant its specific standing might not be questioned, 
but among the specimens before me are many intermediates in which the dorsal 
portion of the fourth segment is blackish leaving very broad posterior and lateral 
margins of white. As to Macquart’s species there seems to be no question as to the 
synonymy. 
