ff. First segment of the antennae short. _P. aeneo-nitens_.
South. _Pothea_ A. et S.
cc. Ocelli cephalad of the hind margins of the eyes; first segment of the antennae stout, second segment divided into many smaller segments. South and west. _Homalocoris maculicollis_, and _Hammatocerus purcis_. HAMMATOCERINae
bb. Hemelytra with a quadrangular or discoidal areole in the corium near the apex of the clavus (fig. 159e).
c. a.n.a.l areole of the membrane not extending as far proximad as the costal areole; basal segment of the antenna thickened, porrect; the other segments slender, folding back beneath the head and the first segment STENOPODINae
d. Head armed with a ramous or furcate spine below each side, caudad of the eyes.
e. First segment of the antenna thickened, apex produced in a spine beyond the insertion of the second segment. Species from Va., Ill. and south. _Pnirontis_ Stal.
ee. First segment of the antenna not produced beyond the insertion of the second segment. _Pygolampis_, N. E. states and south; _Gnathobleda_, S. W. and Mex.
dd. Head unarmed below or armed with a simple spine; rarely with a subfurcate spine at the side of the base. Carolina, Missouri and south. _Stenopoda_, _Schumannia_, _Diaditus_, _Narvesus_, _Oncocephalus_
cc. a.n.a.l areole of membrane extending farther proximad than the costal areole.
d. Ocelli farther apart than the eyes. _A. cra.s.sipes_, widely distributed in the United States; other species occur in the southwest. _Apiomerus_ Hahn.
dd. Ocelli not so far apart as the eyes. ZELINae
e. Sides of mesosternum without a tubercle or fold in front.
f. Fore femur as long as or longer than the hind femur; first segment of the beak much shorter than the second. _Z.
audax_, in the north eastern states; other species south and west. _Zelus_ Fabr.
ff. Fore femur shorter than the hind femur, rarely of equal length, in this case the first segment of the beak as long or longer than the second.
g. First segment of the beak shorter than the second; fore femur a little shorter than the hind femur; the first segment of the beak distinctly longer than the head before the eyes. _P. cinctus_ a widely distributed species (fig. 160). _P. punctipes_, _P. spinicollis_, Cal., Mex. (= _Milyas_) _Pselliopus_ Berg.
gg. First segment of the beak as long or longer than the second.
h. p.r.o.notum armed with spines on the disc.
i. Juga distinctly prominent at the apex and often acute or subacute; fore femur distinctly thickened; hemelytra usually not reaching the apex of the abdomen. _Fitchia aptera_, N. Y., south and west; _F. spinosula_, South; _Rocconata annulicornis_, Texas, etc.
ii. Juga when prominent, obtuse at apex; eyes full width of the head; fore femur not thickened; p.r.o.notum with four spines on posterior lobe. _R. taurus_, Pa., south and west. _Repipta_ Stal.
hh. p.r.o.notum unarmed on the disc.
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 unarmed. _Fitchia_ (in part); _Castolus ferox_, Arizona.
ee. Sides of the mesosternum with a tubercle or 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.
[Ill.u.s.tration: 161. Taxonomic details of Diptera. (_a_) Ventral aspect of abdomen of Cynomyia; (_b_) antenna of Taba.n.u.s; (_c_) ventral aspect of abdomen of Chortophila; (_d_) ventral aspect of abdomen of Stomoxys; (_e_) claw of Aedes (Culex) sylvestris, male; (_f_) claw of Hippoboscid; (_g_) foot of dipterous insect showing empodium developed pulvilliform; (_h_) hind tarsal segment of Simulium vittatum, female; (_i_) foot of dipterous insect showing bristle-like empodium.]
g. Fore tibiae each with three long spines on the ventral side. _S. diadema_ (fig. 159e), 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. p.r.o.notum produced caudad over the scutellum, with a high mesal tuberculate ridge (fig. 19e). A. CRISTATUS. N. Y.
to Cal. and south. ARILUS Hahn.
gg. Caudal lobe of the p.r.o.notum six sided, neither elevated nor produced caudad. _H. america.n.u.s_, Southwest; also several W. I. and Mexican genera. HARPACTOR Lap.
DIPTERA (Mosquitoes, Midges, Flies)
a. Integument leathery, abdominal segments indistinct; wings often wanting; parasitic forms. PUPIPARA
b. Head folding back on the dorsum of the thorax; wingless flies parasitic on bats. Genus _Nycteribia_. NYCTERIBIIDae
bb. Head not folding back upon the dorsum of the thorax; flies either winged or wingless; parasitic on birds and on bats and other mammals.
c. Antennae reduced, wings when present, with distinct parallel veins and outer crossveins; claws simple; palpi leaf-like, projecting in front of the head. Flies chiefly found on bats. Several genera occur in North America. STREBLIDae
[Ill.u.s.tration: 162. Hippobosca equina, 4. After Osborn.]
cc. Antennae more elongate, segments more or less distinctly separated; head sunk into an emargination of the thorax; wings when present with the veins crowded toward the anterior margin; palpi not leaf-like. HIPPOBOSCIDae
d. Wings absent or reduced and not adapted for flight.
e. Wings and halteres (balancers) absent. _M. ovinus_, the sheep tick. _Melophagus_ Latr.
ee. Wing reduced (or cast off), halteres present.
f. Claw bidentate; ocelli present. On deer after the wings are cast off. _L. depressa_. _Lipoptena_ Nitsch
ff. Claw tridentate (fig. 161 f). On _Macropis_. _B.
femorata._ _Brachypteromyia_ Will.
dd. Wings present and adapted for flight.
e. Claws bidentate.
f. Ocelli present; head flat; wings frequently cast off. On birds before casting of the wing. _Lipoptena_ Nitsch.
ff. Ocelli absent; head round; wings present. The horse tick H. EQUINA may attack man (fig. 162). HIPPOBOSCA L.
ee. Claws tridentate (fig. 161 f.).