Aquatic Insects of Michigan

by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan

Gerridae - Water Striders

Introduction

Under construction

Adult males (adapted from Anderson 1990, Gonsoulin 1974, Hilsenhoff 1986, and Polhemus 1996)

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

Limnoporus Stål, 1868

Limnoporus canaliculatus (Say), 1832 Gerris
Limnoporus dissortis (Drake and Harris), 1930 Gerris
Limnoporus rufoscutellatus (Latreille), 1807 Gerris - WI (error?), check for possible Michigan record

Rhagodotarsinae

Rheumatobates Bergroth, 1892

Rheumatobates palosi Blatchley, 1926, as R. rileyi var. palosi
Rheumatobates rileyi Bergroth, 1892

Trepobates Uhler, 1894

Trepobates inermis Esaki, 1926
Trepobates knighti Drake and Harris, 1928
Trepobates pictus (Herrich-Schaeffer), 1847 Halobates
Trepobates subnitidus Esaki, 1926

References

Andersen NM. 1990. Phylogeny and taxonomy of water striders, genus Aquarius Schellenberg (Insecta, Hemiptera, Gerridae), with a new species from Australia. Steenstrupia 16(4):37-81.
Gonsoulin GJ. 1974. Seven families of aquatic and semiaquatic Hemiptera in Louisiana. Part IV. Family Gerridae. Transactions of the American Entomological Society 100(4):513-546.
Hilsenhoff WL. 1986. Semiaquatic Hemiptera of Wisconsin. The Great Lakes Entomologist 19(1):7-19.
Polhemus JT. 1996. Aquatic and semiaquatic Hemiptera, pp. 267-297 in Merritt RW, Cummins KW (editors), An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing Company: Dubuque, Iowa. xiii + 862 pp.

Page created: September 15, 2003 (EB)
Page last reviewed: September 15, 2003 (EB)