Characteristics and Taxonomic Sources
379
l.a. With fully developed wings and wing covers. . . . . . . . . . . . .
. adults 2
. larvae 4
l.b. No wings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.a. Crawling, clinging beetles; no swimming hairs. Elmidae (1-3 mm) . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dryopidae (3-8 mm)
2.b. Active swimmers; legs with fringe of swimming hairs . . . . . . . . . . . 3
3.a. Antennae short, ending in club.
3.b. Antennae long, slender. . . . . .
4.a. Entire body flattened, dishlike.
4.b. Body more cylindrical . . . . .
· . . . . . Hydrophilidae
(water scavenger beetle)
· . . . . . . . Dytiscidae
(predaceous diving beetle)
. . Psephenus
(water penny)
. . . . . . . . 5
5.a. Entire body heavily armored with chitin; very cylindrical; hairless; small
jaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Elmidae
5.b. Abdomen moderately soft with some bristles; large tubular sucking jaws ... 6
6.a. Legs 4-segmented .
6.b. Legs 5-segmented .
Key II: Hemiptera
(True bugs; adults and nymphs aquatic)
l.a. Surface skimmers; antennae longer than head .
l.b. Fully aquatic; antennae shorter than head . . .
. . . . . . . . . . Dytiscidae
(predaceous diving beetle)
· . . . . . Hydrophilidae
(water scavenger beetle)
. ... 2
. ... 4
2.a. First long segment of hind leg much longer than abdomen.
. Gerris
(water strider)
2.b. This segment no longer than abdomen.
. .Veliidae 3
3.a. Abdomen about as wide as thorax. . . .
3.b. Abdomen narrowing sharply posteriorly .
4.a. Wings covering back flatly . . . . .
4.b. Wings rooflike over back; swim upside down.
Key III: Odonata
(Dragon and damsel flies; naiads aquatic)
l.a. No gills at tip of abdomen . . . . . .
l.b. Three platelike gills at tip of abdomen
Key IV: Ephemeroptera
(Mayflies; naiads aquatic)
l.a. Head broad and flat; eyes upward.
l.b. Head rounded; eyes lateral . . . . .
· Microvelia
· Rhagovelia
· .Corixidae
(water boatman)
· . N otonectidae
(back swimmers)
. Dragon flies
. Damsel flies
· Heptageniidae 2
· ... Baetidae 3
379
l.a. With fully developed wings and wing covers. . . . . . . . . . . . .
. adults 2
. larvae 4
l.b. No wings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.a. Crawling, clinging beetles; no swimming hairs. Elmidae (1-3 mm) . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dryopidae (3-8 mm)
2.b. Active swimmers; legs with fringe of swimming hairs . . . . . . . . . . . 3
3.a. Antennae short, ending in club.
3.b. Antennae long, slender. . . . . .
4.a. Entire body flattened, dishlike.
4.b. Body more cylindrical . . . . .
· . . . . . Hydrophilidae
(water scavenger beetle)
· . . . . . . . Dytiscidae
(predaceous diving beetle)
. . Psephenus
(water penny)
. . . . . . . . 5
5.a. Entire body heavily armored with chitin; very cylindrical; hairless; small
jaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Elmidae
5.b. Abdomen moderately soft with some bristles; large tubular sucking jaws ... 6
6.a. Legs 4-segmented .
6.b. Legs 5-segmented .
Key II: Hemiptera
(True bugs; adults and nymphs aquatic)
l.a. Surface skimmers; antennae longer than head .
l.b. Fully aquatic; antennae shorter than head . . .
. . . . . . . . . . Dytiscidae
(predaceous diving beetle)
· . . . . . Hydrophilidae
(water scavenger beetle)
. ... 2
. ... 4
2.a. First long segment of hind leg much longer than abdomen.
. Gerris
(water strider)
2.b. This segment no longer than abdomen.
. .Veliidae 3
3.a. Abdomen about as wide as thorax. . . .
3.b. Abdomen narrowing sharply posteriorly .
4.a. Wings covering back flatly . . . . .
4.b. Wings rooflike over back; swim upside down.
Key III: Odonata
(Dragon and damsel flies; naiads aquatic)
l.a. No gills at tip of abdomen . . . . . .
l.b. Three platelike gills at tip of abdomen
Key IV: Ephemeroptera
(Mayflies; naiads aquatic)
l.a. Head broad and flat; eyes upward.
l.b. Head rounded; eyes lateral . . . . .
· Microvelia
· Rhagovelia
· .Corixidae
(water boatman)
· . N otonectidae
(back swimmers)
. Dragon flies
. Damsel flies
· Heptageniidae 2
· ... Baetidae 3