1.         Compound eyes divided into separate dorsal and ventral segments; second antennal segment             elongate and scoop-shaped. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gyrinidae

            Compound eyes undivided; antennae variable but without scoop-shaped second antennal             segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.         Head produced anteriorly as a rostrum; tarsal formula 4-4-4. . . . . . . . . . . . Curculionidae

            Head not produced as a rostrum; tarsal formula variable. . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.         Elytra covering entire abdomen or exposing only part of last abdominal tergite.. . . . . . . . . .6

            Elytra truncate, exposing at least 2 entire abdominal tergites. . . . . . . . . . . . . . . . . . . . . . . 4

4.         Antennae with 11 (rarely 10) segments, terminal segment no longer than combinied length             of 2 preceding segments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Staphylinidae

            Antennae with 8 segments, terminal segment as long as combined length of 4 preceding             segments; minute beetles, less han 1.5 mm long; hind coxal plates widely separated. . . . . . .             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .Hydroscapidae (not known for Ohio)

5.         Hind coxae expanded as broad flattened plates covering all or part of abdominal sternites. . . .             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Haliplidae

            Hind coxae sometimes extending posteriorly along midline but never as broad plates. . . . . 6

6.         Hind coxae with medial portion extending posteriorly to divide 1st abdominal sternite into             later sclerites; prothorax with distinct notopleral sutures. . . . . . . . . . . . . . . . . . . . . . . . . . 7

            Hind coxae not extending posteriorly to divide 1st abdomainal sternite; notopleural sutures             almost always absent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

7.         Hind tarsi and usually tibiae flattened, streamlined and bearing loong stiff swimming bristles. .             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

            Hind tibiae and tarsi cylindrical or subclindrical in cross section, without long, stiff swimming             bristles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

8.         Fore and middle tarsi with 5 segments, segment 4 similar in size to segment 3; scutellum             concealed or exposed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

            Fore and middle sarsi with 4 segments or with segment 4 very small, concealed between             lobes of segment 3; scutellum concealed except in Celina. . . . . . . . . . .. Dyticidae (in part)

9.         Hind tarsi with 2 similar claws; scutellum concealed. . . . . . . . . . . . . . . . . . . . . . Noteridae

            Hind tarsi with single claw; if 2 claws,scutellum exposed. . . . . . . . . . . . Dyticidae (in part)

10.         Abdomen with 5-6 visible sternites; antennal club with 3 segments. . . . . . . Hydrophilidae

            Abdomen with 6-7 visible sternites; antennal club with 5 segments. . . . . . . . . Hydraenidae

11.        Tarsal formula 5-5-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

            Tarsal formula 5-5-4 or less. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chrysomelidae

12.        Abdomen with 5-7 visible sternites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

            Abdomen with at east 8 visible sternites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lampyridae

13.        Prosternum expanded anteriorly as prominent lobe beneath head, head usually contracted             into thorax concealing antennnae and eyes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

            Prosternum not markedly expanded anteiorly beneath head, antennae clearly visible. . . . . 17

14.        Antennae usually thick, with enlarged basal segment, about as long as head. . . . . . . . . . 15

            Antennae filiform or serrate, much longer than head. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

15.        Antennae with 10 or fewer segments; hind coxae contiguous . . . . . . . . . . . . . . . . . . . . . . .             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lutrochidae, Lutrochus laticeps

            Antennae with 11 segments (hard to see); hind coxae separated. . . . . . Dryopidae (in part)

16.        Anterior coxae transverse with trochantin visible; antennae (if visible) very short, thick, with             enlarged basal segment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dryopidae (in part)

            Anterior coxae round, trochantin concealed, antennae slender, filiform. . . .Elmidae (in part)

17.        Tarsi with 4th segment deeply bilobed. . . . . . . . . . . . . . . . . .. . . . . Scirtidae, Cyphon sp.

            Tarsi usually filiform, 4th segment not bilobed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

18.        Antennae never concealed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

            Antennae filiform or clavate, partly concealed within prosternum. . . . . . . .Elmidae(in part)

19.        Abdomen with 6 or 7 sternites; maxillarly palp with 2nd segment longer than next 2                         combined. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Psephenidae (in part)

            Abdomen with 5 sternites; maxillary palp with 2nd segment much shorter than next 2             combined. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

20.        Head with antennae inserted close together between eyes constricting clypeus from frons. . .             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Psephenidae (in part)

            Head with antennae inserted below eyes, cont constricting clypeus. . . . . . . . . . . . . . . . . . . .             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ptilodactylidae, Anchytarsus bicolor

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