284 
Hominoxious A rthropods 
i. Spines on each apical angle of the penultimate abdominal 
segment. A. cinereus, Pa., and south. . Atrachelus A. et S. 
ii. Apical angle of the penultimate abdominal segment un¬ 
armed. Fitchia (in part); Castolus *erox, Arizona, 
ee. Sides of the mesosternum with a tubercle of fold in front at the hind 
angles of the prosternum; first segment of the beak longer than 
the part of the head cephalad of the eyes, 
f. Fore femur thickened, densely granulated; hind femur unarmed. 
161. Taxonomic details of Diptera. (a) Ventral aspect of abdomen of Cynomyia; 
( b ) antenna of Tabanus; (c) ventral aspect of abdomen of Choitophila; (d) 
ventral aspect of abdomen of Stomoxys; ( e ) claw of Aedes (Culex) sylves- 
tris, male; (f) claw of Hippoboscid; ( g ) foot of dipterous insect showing 
empodimm developed pulvllliform; {h) hind tarsal segment of Simulium 
vittatum, female; (*) foot of dipterous insect showing bristle-like empodium. 
g. Fore tibiae each with three long spines on the ventral side. 
S. diadema (fig. I59e), a widely distributed species; and 
several southwestern species. Sinea A. et S. 
gg. Fore tibiae unarmed. A. multispinosa, widely distributed; 
A. tabida, Cal. Acholla Stal. 
ff. Fore femur unarmed, rarely a little thickened, a little granulated, 
g. Pronotum produced caudad over the scutellum, with a high 
mesal tuberculate ridge (fig. 19c). A. cristatus. N. Y. to 
Cal. and south.Arilus Hahn. 
gg. Caudal lobe of the pronotum six sided, neither elevated nor 
produced caudad. H. americanus, Southwest; also several 
W. I. and Mexican genera.Harpactor Lap. 
