Hydnobius Schmidt 1841

Key to North American species of Hydnobius (males)

1 Parameres narrow in apical one-half, straight (Figs. 18, 40)...................................................................................... 2

- Parameres not as above, broad, sinuate, or curved (Figs. 25, 33, 48)......................................................................... 3

2 Median lobe of aedeagus gradually narrowing to acute apex (Fig. 18); internal sac with two elongate rows of dark setae (Fig. 18), setae also visible posteriorly when internal sac is inverted; antennomere 7 clearly broader than antennomere 8 (Fig. 15).................................................................................................................................. H. substriatus

- Median lobe of aedeagus abruptly narrowing to acute apex (Fig. 40); internal sac densely covered with small scalelike setae (Fig. 40); antennomere 7 narrow, hardly broader than antennomere 8 (Fig. 37)......................... H. laticeps

3 Parameres broad or sinuate (Figs. 25, 33, 59); transcontinental or eastern species..................................................... 4

- Parameres narrow and outwardly curved (Figs. 48, 54); western species.................................................................. 6

4 Parameres broad, with apical one-half concave medially (Fig. 25); small body size, length of pronotum + elytra less than 2.2 mm................................................................................................................................................ H. pumilus

- Parameres not as above, larger body size, length of pronotum + elytra greater than 2.2 mm..................................... 5

5 Parameres sinuate (Fig. 33); internal sac with a pair of sclerotized oblong lobes (Fig. 33), lobes may be visible also when internal sac is inverted; male protibial spur broad (Fig. 31)........................................................... H. longidens

- Parameres straight (Fig. 59); internal sac does not contain sclerotized lobes; male protibial spur unmodified............................................................................................................................................................................ H. autumnalis

6 Mesoventrite with median carina..................................................................................................................... H. kiseri

- Mesoventrite without median carina.......................................................................................................... H. acarinus