1a |
a. Inner margins of eyes sinuate or concave behind the
middle |
2 |
b. Body comparatively long and narrow, length > 4.7 mm |
1b |
a. Inner margins of eyes rounded, convex |
12 |
b. Body comparatively short and broad, length < 4.8 mm |
|
2a (1a) |
a. Pronotum shiny |
Neogerris hesione (Kirkaldy) |
also: Length of second prothoracic tarsal segment 2x length of segment
1; head with broad, transverse, basal pale mark; length 4.7-6.5mm |
2b |
a. Pronotum dull |
3 |
also: Length of
second prothoracic tarsal segment < 1.5x length of
segment 1; head with a narrow, broadly v-shaped pale mark at base |
|
3a(2b) |
Antennal segment 1 < 0.8x the combined length of antennal
segments 2-3 |
Limnoporus Stål,
4 |
3b |
Antennal segment 1 > 0.9x the combined length of
antennal segments 2-3 |
5 |
|
4a |
Body length 7.5-11.0 mm |
Limnoporus canaliculatus (Say) |
4b |
Body length 11.5-15.1 mm |
Limnoporus dissortis (Drake and Harris) |
|
5a(3b) |
a. Hind tibia at least 4.0x the length of hind tarsal segment 1 |
Aquarius Schellenberg, 6 |
b. Prominent connexival spines that curve slightly outward |
c. Length > 11.0 mm |
5b |
a. Hind tibia < 3.2x the length of hind tarsal segment 1 |
Gerris Fabricius, 7 |
b. Without prominent connexival spines |
c. Length < 10.7
mm |
|
6a(5a) |
a. Ant1 subequal to combined length of Ant2-3 |
Aquarius remigis (Say) |
b. In ventral view, hind margin of male Ab7 sternum doubly emarginated,
with a distinct notch in middle |
c. In ventral view, Ab8 sternum very large, with a distinct median
keel |
d. Greatest width (across mesoacetabula) > 0.25x body length |
6b |
a. Ant1 distinctly longer than combined lengths of Ant2-3 |
Aquarius conformis (Uhler) |
b. In ventral view, hind margin of male Ab7 roundly emarginated |
c. In ventral view, Ab8 sternum not modified |
d. Greatest width
(across mesoacetabula) < 0.25x body length |
|
7a(5b) |
Pronotum with a narrow lateral pale stripe |
8 |
7a |
Pronotum without a lateral pale stripe |
9 |
|
8a(7a) |
a. Width of first genital segment of male about equal to its length |
Gerris buenoi Kirkaldy |
b. Notch in last
abdominal sternum of male subrectangular, width > length |
c. Connexival spines of female not reflexed dorsally |
d. Ant2 slightly longer than Ant3, combined length of Ant2-3 slightly
longer than Ant1 |
e. Body length about 6.8-8.6 mm |
8b |
a. Width of frist gential segment of male 2x that of its length |
Gerris argenticollis Parshley |
b. Notch in last abdominal sternum of male narrow, with its sides diverging
posteriorly |
c. Connexival spines of female reflexed dorsally |
d. Length of Ant2 = Ant3, combined length of Ant2-3 = Ant1 |
e. Body length about 7.0-8.5 mm |
|
9a(7a) |
a. First gential segment of male without a conspicuous, ventral brush
of long hairs |
Gerris comatus Drake and Hottes |
b. Connexival spines of female not reaching the apex of the first gential
segment, and with long (0.1 mm), dark setae at and near the tip |
c. Body length about 8.5-10.6 mm |
9b |
a. First gential segment of male without a conspicuous ventral brush
of long hairs |
10 |
b. Connexival spines
of female with setae at the tip short (< 0.05
mm), if slightly longer then the tips of spines reach or surpass the
apex of the first gential segment |
|
10a(9b) |
a. Male with omphalium strongly protuberant |
Gerris alacris Hussey |
b. Connexvial spines of female short, not reaching the midpoint of
the first gential segment |
c. Body length about 7.0-10.00 mm |
10b |
a. Male with omphalium not protuberant |
11 |
b. Connexival spines of female longer, projecting poast the midpoint
of the frist gential segment |
|
11a(10b) |
a. Male with first gential segment impressed on each side ventrally
to form a broad median carina |
Gerris marginatus Say |
b. Connexival spines of female porject to, or poast, the tip of the
first gential segment, and are covered at the tip with setae about 0.05
mm long |
c. Body length about 9.1-10.8 mm |
11b |
a. Male with first genital segment plump, evenly rounded ventrally,
and with a posterior convexity |
Gerris insperatus Drake and Hottes |
b. Connexival spines of female do not project posteriorly to the tip
of the first gential segment, and are covered at the tip with setae only
about 0.03 mm long |
c. Body length about 8.7-10.1 mm |
|
12a(1b) |
a. Ant1 subequal to Ant2-4 |
Metrobates hesperius Uhler |
b. Body length about 4.2-4.8 mm |
12b |
a. Ant1 << Ant2-4 |
13 |
|
13a(12b) |
a. Ant3 bearing stiff bristles longer than the diameter of the segment |
Rheumatobates Bergrath,
14 |
b. Ant4 distinctly subequal to, or shorter than, Ant3 |
c. Male raptorial antennae |
also: Metafemora distinctly bowed, with basal half bearing distinct
tufts of long hairs, at least some longer than the width of the metafemur |
13b |
a. Ant3 bearing only short pubescence, at most with three stout brisles
shorther than the width of the segment |
Trepobates Uhler,
15 |
b. Length of Ant4 >> Ant3 |
c. Male without raptorial antennae |
Rheumatobates |
14a(13a) |
Ant4 armed with a distinct tooth at, or slightly beyond, the middle |
Rheumatobates rileyi Bergroth |
14b |
Ant4 armed with a distinct tooth basal to the middle of the segment |
Rheumatobates palosi Blatchly |
Trepobates |
15a(13b) |
Mesonotum without a light-colored lateral stripe posterior to the dark
lateral pronotal stripe |
Trepobates subnitidus Esaki |
15b |
Mesonotum with a light-colored lateral stripe posterior to the dark
lateral pronotal stripe, the mesonotal stripe either very short or extending
the length of the mesonotum |
16 |
|
16a(15b) |
Mesonotum with a lateral stripe extending the entire length of the
mesonotum |
Trepobates pictus (Herrich-Schaeffer) |
16b |
Mesonotum with the lateral stripe very short |
17 |
|
17a(16b) |
a. Ab8 tergite with dorsal pubesence of male pale |
Trepobates inermis Esaki |
b. Female never with connexival spines on the genital segments |
17b |
a. Ab8 tergite with dorsal pubesence of male darker |
Trepobates knighti Drake and Harris |
b. Female usually with connexival spines on the genital segments |
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