1919] nine: Genus Erax 127 



rectness of the extensive distribution of CEstuans which is given 

 as occurring from New England to Guiana, including records 

 for the West Indies. 



Seven species are recognized in the material at hand from the 

 West Indies, mainly based on a study of male genitalia, and 

 none of them are regarded as the common cBstuans Linne of the 

 Eastern United States. The following key will aid in 

 separating them. 



1. Mystax pale, scutellum with white pile and bristles- 2 



Mystax in large part black, scutellum with black bristles 4 



2. Mystax straw yellow nigritarsis n. sp. 



Mystax white 3 



3. Hypopygium long and narrow portoricensis n. sp. 



Hypopygium short and tumid rufitibia Macq. 



4. Male costa distinctly thickened and dilated beyond the tip of the auxiliary 



vein, wings distinctly reddish 5 



Male costa not thickened and dilated, wings nearly hyaline 6 



5. Hypopygium much enlarged, rather large robust species stylatus Fabr. 



Hypopygium small, species 16 millimeters in total length nigrimystaceus Macq. 



6. Hypopygium short and tumid, shining black all over rufitibia Macq. 



Hypopygium elongate 7 



7. Large species, hypopygium much elongate fulvibarbis Macq^ 



Medium sized species, hypopygium only slightly elongate. , . haloesus W. K. 



Erax stylatus Fabricius. 



Total length, male 20 to 26 millimeters, female, 18 to 28 millimeters. 

 Mystax composed of numerous black bristles intermixed with fine 

 white hair, beard white, palpi with white hairs, but mixed in is an 

 occasional black one, in some specimens more than others. Femora 

 entirely black, tibiae yellow, each very narrowly black at apex, tibiae 

 somewhat darker than the tibiae and with numerous black bristles; 

 wings distinctly brown. 



Male genitalia large, fully as long as abdominal segments five, six 

 and seven. See Figure 32. Costal border of the wing distinctly 

 dilated beyond the tip of the auxiliary vein. Usually no stump on 

 anterior branch of the third vein, although in some cases there is a very 

 short one. 



Female genitalia shining black, about as long as segments four to 

 seven, wings almost hyaline, costal border of wing not dilated, anterior 

 branch of the third vein with a distinct stump. 



Specimens from several places in Cuba, from Porto Rico, 

 and one male from extreme southern Florida, indicating a wide 

 range. The Florida specimen is peculiar in having the whole 

 abdomen from the apex of the second segment to the genitalia 

 silvery, but I can find no other differences. 



Although stylatus has not been recognized by most authors, 

 Wiedmann's figure should help in its determination. With more 



