Explanation of Names
Paracosmus Osten Sacken 1877
5 spp. in 2 subgenera, all in our area(1)
rubicundus Melander 1950. Range: AZ, CA (also Sonora, Mexico)
edwardsii (Loew) 1872. Range: CA, UT
insolens Coquillett 1891. Range: CA, NV
morrisoni Osten Saken 1887. Range: AZ, CA, NV, TX (also Sonora, Mexico)
similis Hall 1957. Range: CA
Key to Paracosmus
(adapted from Melander and Cole(2)
1a) Abdomen principally reddish-yellow with whitish posterior bands; 1st antenna segment yellow, 2nd & 3rd segments black.......rubicundus
1b) Abdomen principally black with posterior white to yellow bands; antenna entirely black........2
2a) Femora and tibiae black; a dense tuft of white pile anterior to base of halteres; anterior crossvein r-m near middle of discal cell.........insolens
2b) Femora and tibiae reddish; no dense tuft of white pile anterior to base of halteres; anterior crossvein r-m distinctly beyond middle of discal cell.........3
3a) Whitish-to yellowish posterior tergal bands widened medially into forward-pointing triangles, decreasing in size towards posterior tergites; haltere knobs black on anterior face, white on posterior face; 3rd antennal segment not widest beyond middle.........edwardsii
3b) Whitish-to yellowish posterior tergal bands more-or-less uniform in width, narrowing somewhat towards posterior tergites; haltere knobs yellowish to white on both faces (at least in morrisoni); 3rd antennal segment widest beyond middle (in similis), or not (in morrisoni).........4
4a) Haltere knobs yellowish to white on both faces; 3rd antennal segment not widest beyond middle; face (i.e. below antennae) at least partly pale.........morrisoni
4b) (Haltere color uncertain); 3rd antennal segment widest beyond middle; face black; (east of Sierra Nevada?)........similis
sw. US (TX-UT-CA) & Mexico (Sonora)(1)
Melander(1950) had reservations regarding the distinctness of edwardsii and morrisoni, stating:
"There is much intergrading between edwardsii and morrisoni, so it is doubtful if two species exist. The size of the white triangles on the abdomen varies and especially in the females has a tendency to flatten out; the color of the halteres is not reliable; and the extent of the pollen on the front of the female is subject to much variation."
However, the 2015 revision of the catalog for Bombyliidae by Evenhuis & Greathead(1)
maintains listings for both species.
Coquillett, D. W. (1890) New Bombylidae of the group Paracosmus
. West-American Scientist, Vol. 7, pp. 219-222 (Full Text at Google Books
Hall, J. C. (1957) Notes and descriptions of new California Bombyliidae (Diptera). Pan-Pac. Entomologist 33: 141–48.
Melander A.L. (1950) Taxonomic notes on some smaller Bombyliidae (Diptera). Pan-Pacific Entomologist 26: 139-156.
Description of genus Paracosmus
from the 1973 "Bee Flies of the World" by Hull(3)