Water Striders) of Idaho (Heteroptera)

Home , Aquarius (bug), Aquarius remigis, Gerridae, Gerrinae, Gerris, Gerris marginatus

Great Basin Naturalist

Volume 49 Number 2 Article 14

4-30-1989

Gerridae (water striders) of Idaho (Heteroptera)

R. C. Biggam University of Idaho, Moscow

M. A. Brusven University of Idaho, Moscow

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Recommended Citation Biggam, R. C. and Brusven, M. A. (1989) "Gerridae (water striders) of Idaho (Heteroptera)," Great Basin Naturalist: Vol. 49 : No. 2 , Article 14. Available at: https://scholarsarchive.byu.edu/gbn/vol49/iss2/14

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. GERRIDAE (WATER STRIDERS) OF IDAHO (HETEROPTERA) 1

R. C. Biggam" and M. A. Brusven"

Abstract. —A biosystematic study on the Gerridae of Idaho was undertaken to clarify and describe the taxonomy, species distribution, and biology of this aquatic hemipteran family. Three genera and 7 species were collected in the state. Keys to three genera and 10 species are provided. General descriptions, diagnoses, and distributional ranges are given for species occurring within and adjacent to Idaho.

Special interest in aquatic and subaquatic (Scudder 1969, 1971), brackish coastal waters Heteroptera by the authors and recently pub- (Vepsalainen 1973, Andersen 1975, Cobben lished papers on the Gerridae of Montana 1960), and the open ocean (Andersen and Pol- (Roemhild 1976) and Oregon and Washington hemus 1976). Five species of the genus Halo- (Stonedahl and Lattin 1982) prompted this bates have been collected hundreds of miles taxonomic study on the Gerridae of Idaho. from the nearest land (Cheng 1974), making The ubiquitous nature, conspicuous habits, them one of the few insects to successfully predaceous activities, and nutritive value of occupy the open ocean. Vepsalainen (1973), gerrids to higher trophic levels make them an Calabrese (1977), and Spence and Scudder important group in aquatic and semiaquatic (1980) found that gerrids display habitat pref- ecosystems. erences. Strict habitat association is the most The purposes of this study were to deter- important factor in ecological species separa- mine the distributions of species occurring in tion and coexistence (Spence and Scudder Idaho, clarify taxonomic differences between 1980, Spence 1983). related species occurring in or adjacent to the state, provide a diagnostic key for the identifi- Biology and Life History cation of species, and provide information on habitat affinities. Three genera and seven spe- Gerrids are opportunistic predators (Jamie- cies of Gerridae are recorded in the state. son and Scudder 1977) on other insects of the neuston community and terrestrial inverte- brates that fall into the water. They are also Classification and Distribution known to feed on fruits and berries (Riley Approximately 488 species of Gerridae in 1918). Live prey are preferred, but scaveng- 55 genera occur throughout the world (An- ing and cannibalism are probably necessary dersen 1982). Five subfamilies were recog- for some to survive. Coastal gerrids may feed nized by Hungerford and Matsuda (1960) and on windblown terrestrial insects found on the eight by Andersen (1975, 1982); two occur in sea (Andersen and Polhemus 1976). Ocean- Idaho and the Pacific Northwest (Gerrinae going Halobates feed on coelenterates (Savi- and Trepobatinae). lov 1967). Cannibalism occurs in most species

The family Gerridae is worldwide in distri- and is usually the result of overcrowding, food bution except for the polar regions. Gerrids shortage, or vulnerability during molting (Ri- live on the surfaces of rivers, mountain ley 1922a, 1922b, 1925, Stonedahl and Lattin streams, and warm ponds (Fairbairn 1985a), 1982). Gerrids detect their prey and mates by lakes, reservoirs, irrigation canals, and hot orientation to surface waves caused by the springs (Calabrese and Tallerico 1982), road object of intent (Murphy 1971a, 1971b, 1971c, puddles, ditches, sinkhole ponds, marshes, Weber 1930, Wilcox 1972, 1979, Lawry 1973). and swamps (Herring 1950, 1951), saline lakes The prey is quickly grasped by the raptorial

'Approved by the director of the Idaho Agricultural Experiment Station as Research Paper #8876 2 Department of Plant. Soil and Entomological Sciences. University of Idaho, Moscow. Idaho 83843.

259 260 Great Basin Naturalist Vol. 49, No. 2 forelegs, after which the cutting, mandibular 1961, 1963, Vepsaliiinen 1971a, 1971b, 1974a, stylets of the forward-extended rostrum are 1974b, Andersen 1973, Jarvinen 1976, Jar- inserted into the prey (Cobben 1978). These vinen and Vepsaliiinen 1976) where apterous stylets also serve in the transfer of enzymatic to macropterous forms can occur. Apterous secretions into the prey and the extraction of populations usually indicate a stable popula- the prey's body fluids (Cheng 1967a, 1974). tion and habitat. Macropterous populations Gerrids have hemimetabolous or gradual are common in unstable or confined habitats development; the immature stage is a nymph. such as ponds or lakes. In populations with Eggs are attached to submerged vegetation or multiple generations, early apterous genera- other substrates either singly or in clusters tions often produce macropterous individuals (Hungerford 1920, Cobben 1968, Andersen for population dispersion (Brinkhurst 1963). and Polhemus 1976). One European species, Macropterous forms usually overwinter as Gerris najas De Geer, attaches its eggs to lake adults and reproduce the following season. bottom substrates (Brinkhurst 1960), whereas Occasionally, brachypterous and micropter- of the subfamily Bhagadotarsinae members ous forms of the same species may occur to- insert their eggs directly into plant tissue (Sil- gether, the result of population density, cli- vey 1931). The eggs, usually white when laid, matic changes, and/or habitat instability. turn to amber with age and range in size from Vepsaliiinen (1971a, 1971b) observed that an 1.0 X 0.33 to 1.6 X 0.5 (Herring mm mm environmental switching mechanism caused 1961). The eggs usually hatch within 14 days by day length, temperature, and illumination (Torre-Bueno 1917a, 1917b, Hungerford rhythm is the probable cause of the varying 1920, Hoffman 1924, Bobb 1951, Herring wing lengths from one generation to the next 1961, Cheng 1967b). An egg burster is used in bivoltine or trivoltine populations. by the first instar nymph to escape from the Gerrid flight activity has been reported by chorion (Hungerford 1920, Cobben 1968). Biley (1920), Leech (1970), Callahan (1974), The newly hatched nymphs make their way to and Spence and Scudder (1980). Biley (1925) the surface, break the surface tension, and lists food deficiency, drought, and overcrowd- begin life on the waters surface. Depending ing as important factors influencing flight. on environmental factors, one to six genera- also result in compensa- tions per year have been noted (Torre-Bueno Overcrowding can 1917a, Hoffman 1924, Cheng 1967b, Cheng tory upstream dispersal (Fairbairn 1985b). and Fernando 1970, Bobb 1974, Vepsaliiinen Shortened day lengths during larval develop- 1974b, 1974c, Callahan 1974, Polhemus and ment induce diapause (Vepsaliiinen 1971b, Chapman 1979, Spence and Scudder 1980). 1974a, 1974d). Lee et al. (1975) reported that The nymphs have five instars or molts and triglycerides were metabolized during hiber- require 21 to 44 days to achieve adulthood nation in G. remigis Say. (Penn and Goldsmith 1950, Bobb 1951, Her- Gerrids are fed upon by frogs (Drake 1914, ring 1961). Torre-Bueno 1917b, Biley 1925, Callahan

Spence et al. (1980b) reported that temper- 1974), fish and Dytiscus beetles (Biley 1925), ature is very important in development. They ducks (McAtee 1918, Mabbot 1920, Anderson observed several species basking underwater 1932), shorebirds (Wetmore 1925), swallows during low air temperatures, presumably to (Beal 1918), trout (Callahan 1974), and hedge- increase gonad development (1980a). The hogs (Obrtel and Holisova 1981). The senior nymphs are similar in appearance to the author observed Grylloblatta campodeifor- adults except in size, body proportion, near mis Walker (Orthoptera: Grylloblattidae) absence of external genitalic structures, lack feeding on Gerris remigis Say. Cooper (1984), of scent glands, and presence of only one although never observing trout actually feed- tarsal segment per leg. After ecdysis via a ing on gerrids in the wild, reported fish read- Y-shaped suture on the thorax (Cheng 1967b), ily taking experimentally disabled specimens. the adults remain teneral for several days, Some gerrids will attempt to escape predation thus leaving themselves vulnerable to preda- by feigning death (Essenberg 1915, Biley tion and cannibalism (Andersen 1973). 1921, Callahan 1974). Gerrids can inflict a Wing polymorphism in the adult stage is painful bite with their beak, and the pain can prevalent in most species (Brinkhurst 1959, be long lasting. April 1989 Biggam, Brusven: Idaho Water Striders 261

Table 1. The taxa, habitats, trophic relationships, and seasonal occurrences ol the Gerridae of Idaho.

Taxa 262 Great Basin Naturalist Vol. 49, No. 2

A general overview of habitat, trophic rela- exceeds the apex of the abdomen. Also, the tionships, and seasonal occurrence for the middle legs are attached much closer to the

Idaho species is given in Table 1. General hind legs in the gerrids; veliids have the mid- distribution is discussed for each species. dle legs attached approximately midway between the front and hind legs. Gerrids have a General Description and Diagnosis single scent gland opening on the metaster- Members of the family Gerridae, known num; veliids have two scent gland openings, to many as water striders, pond skaters, or delineated by a pair of channels that run lat- wherrymen, are small- to medium-sized in- erad and end anterior to the hind coxae. The sects (6.65-20.0 mm) with narrow, elongate most reliable criterion for separating these bodies and long legs. The head is shorter than two families is the sclerotizaton of the vesica of the pronotum and mesonotum combined. A the aedeagus in gerrids and its absence in four-segmented, filiform antenna is inserted veliids (Polhemus and Chapman 1979, China on either side of the head behind the large, 1957). Female gerrids have the second gono- rounded, compound eyes; ocelli are absent. coxites absent, while veliids have them well The rostrum or beak is four-segmented. The developed (Scudder 1959). The Idaho gerrids thorax is variable according to the degree of can easily be separated from the veliids by wing development. Apterous, brachypterous, the absence of the metathoracic scent gland and macropterous forms occur in many spe- channels. cies. The forelegs are short and raptorial, Key to the Species of Adult Idaho Gerridae whereas the middle and hind legs are long and 1. Inner margins of eyes sinuate or concave pos- slender and have two tarsal segments present teromedially in dorsal view (Fig. 1); first anten- in the adults; the nymphs have one segment. nal segment shorter than remaining three com- Tarsal claws are preapical. The procoxae are bined; abdomen elongate, segments not remote from the meso- and metacoxae. A me- dorsoventrally flattened; ground color black to brown with various gold markings 2 dian scent gland opening on the metaster- — Inner margin of eyes convexly rounded postero- num, the omphalium, is found in most gerrids medially in dorsal view (Fig. 2); first antennal Rhagadotarsi- but is absent in the subfamilies segment longer than remaining three com- nae and many Trepobatinae. A velvety gray to bined; abdomen short, dorsoventrally flattened, dark brown pile of hydrofnge hairs covers appearing atrophied; ground color grey with most of the body. Cheng (1973) found two black markings Metrobates trux infuscatus Usinger types of hairs in Halobates: (1) macrotrichia 2(1). Length of first antennal segment less than seg- (long, slender hairs) and (2) microtrichia ments two and three combined; males with ab- Polhemus (hooklike hairs). Andersen and dominal sternite six evenly emarginate posteri- (1976) reported that most water striders have orly (Fig. 3); female connexival spines of hairs similar to those found by Cheng. abdominal segment six reaching to or beyond middle of last genital segment (Fig. 4) The gerrids differ from the families Corixi- Limnoporus notabilis (Drake & Hottes) dae, Nepidae, Belostomatidae, Ochteridae, — Length of first antennal segment equal to or Gelastocoridae, Naucoridae, Notonectidae, greater than segments two and three combined; and Pleidae in having the antennae longer male with abdominal sternite six sinuately emar- than the head. Gerrids differ from Saldidae in ginate posteriorly (Figs. 5, 9, 12, 17); female having the hind coxae smaller, more conical or connexival spines of abdominal segment six not reaching middle of last genital segment 3 cylindrical, and freely rotatory as compared to Species large (exceeding 12 mm); abdominal saldids, which have transverse, fixed coxae. 3(2). sternite seven of male with medial keel promi- Gerrids differ from the Macroveliidae, Meso- nent and elevated (Fig. 5) veliidae, Hebridae, and Hydrometridae in Gerris (Aquarius) remigis Say having their tarsal claws inserted preapically — Species small (under 12 mm); abdominal stern- on the last tarsal segment, a character shared ite seven of male with medial keel slightly with the family Veliidae. Although gerrids are prominent (Figs. 12, 17) or absent (Fig. 9) 4 similar to veliids in general appearance, they 4(3). Pronotum entirely dark, lacking yellowish to russet brown anterolateral stripes immediately differ markedly in the length of the hind posterior to compound eyes; if pale stripes femur. In Idaho veliids, the hind femur present, then basal three-fourths of first anten- scarcely, if at all, surpasses the tip of the abdo- nal segment with inner and outer surfaces hav-

men, while in gerrids, the hind femur greatly ing narrow, longitudinal, dark stripes (Fig. 7) . . . 8 April 1989 BlGGAM. BRUSVEN: Idaho Water Striders 263

— Pronotum with yellowish to russet brown Subfamily Gerrinae anterolateral stripes immediately posterior to compound eyes (Fig. 6); basal three-fourths of Andersen (1975) recognized one of two

first antennal segment entirely black (Fig. 8) . . . 5 tribes (the Gerrini) and four genera in North 5(4). Abdominal sternite seven of male as long as America. The genera Limnoporus and Gerris broad; posterior, median notch on abdominal are the only representatives this sternite six subrectangular (Fig. 9); female with of subfamily posterolateral angles of tergite six not produced and of the tribe Gerrini in Idaho. into distinct connexival spines; abdominal sternite seven subrectangular, the posterior edges of Genus Gerris Fabricius each valve obtuse (Fig. 10) Gerris(Gerris) buenoi Kirkaldy Gerris Fabricius, 1794. Entomol. Syst. 4: 188. Type spe- — Abdominal sternite seven of male longer than cies: Cimex lacustris Linnaeus, 1758. Designated broad; posterior, median notch on abdominal by Latreille, 1810. sternite six evenly rounded (Figs. 12, 17); fe- Aquarius Schellenberg, 1800. Das geschlect der Land male with posterolateral angles of tergite six und Wasserwanzen, p. 25 (= subgenus). produced into distinct connexival spines; ab- Hygrotrechus Stal, 1868. Ofvers. K. Vet.-Akad. Forh 25: dominal sternite seven triangular, the posterior r 395 ( Aquarius). edges of each valve acute (Fig. 6 11) Limnotrechus Stal, 1868. Ofvers, K. Vet.-Akad. Forh 25: 6(5). Abdominal sternite seven of male with longitu- 395.

dinal rows of long hairs on either side of ventral Ures Distant, 1910. Fuana British India, Rhynchota 5: keel (Fig. 12); pale area along dorsolateral mar- 149. gins of abdominal sternites extending the length Gerriselloides Hungerford & Matsuda, 1958. Entomol. of the abdomen (Fig. 13) News 69: 259 (= subgenus). Gerris (Gerris) incognitas Drake & Hottes — Abdominal sternite seven of male lacking long This is the most common and widely dis- hairs on either side of ventral keel; pale area tributed genus of Gerridae in the world. Fif- along dorsolateral margins of abdominal stern- teen species are known from the Nearctic re- ites only on segments five, six, and seven (Fig. gion, and nine were recorded from Idaho by 14) . 7 Drake and Harris (1934). One of these was 7(6). Corners of abdominal tergites with tufts of silvery pubescense (visible only on dry, degreased transferred to the genus Limnoporus by An- specimens) (Fig. 15); connexival spines of female dersen (1975). Two others, G. remigis Say and curving slightly inward and upward G. nyctalis Drake & Hottes, are combined Gerris (Gerris) gillettei Lethierry & Severin under the former name in this paper following — Corners of abdominal tergites without tufts of silvery pubescence; connexival spines of female the suggestion of Stonedahl and Lattin (1982). pointed almost vertically Gerris marginatus Say, recorded from Idaho Gerris (Gerris) pingreensis Drake & Hottes 1 by Drake and Harris (1934), is believed not to 8(4). Disc of pronotum with uniform, minute, gold occur west of the Continental Divide except specks not interrupted by two longitudinal for a single specimen collected in bands of reflective, silvery setae (visible only on western dry, degreased specimens); connexial spines of Montana. An additional three species are in- female strongly curved inward, not reaching cluded in the key as possibly occurring in the apex of abdominal tergite seven state. Sprague (1967), Scudder and Jamieson Gerris (Gerris) incurvatus Drake & Hottes (1972), and Calabrese (1974a) described the — Disc of pronotum with uniform, minute, gold specks interrupted by two longitudinal bands of nymphs of most North American species. reflective, silvery setae (Fig. 16) (visible only on dry, degreased specimens); connexival spines of Gerris (Aquarius) remigis Say

female not strongly curved inward, reaching Figs. 1, 5 apex of abdominal tergite seven 9 Gerris remigis Say, 1832. Descriptions of new species of 9(8). Abdominal sternite seven of male with distinct, heteropterous Hemiptera of North America, New circular, raised tufts of hair on either side of Harmony, Indiana. Page 35 in The complete writ- median, ventral keel (Fig. 17); connexival spines ings of Thomas Say on the entomology of North of female strongly incurved with apices clothed America. L. LeConte, ed. Vol I. 362 pp. Bail- with stiff hairs (Fig. 18) J. 4 liere Brothers, New York. (Types destroyed). Gerris (Gerris) comatus Drake and Hottes Gerris orba Stal, 1859. K. Sven. Fregatten Eugenies — Abdominal sternite seven of male lacking dis- Resa Omkring Jordon, Zool. 4: 264. tinct tufts of hair on either side of median, ven- Hygrotrechus robustus Uhler, 1871a. Amer. Sci. (3)1: tral keel; connexival spines of female not J. 105. strongly incurved with apices lacking stiff hairs 3 Gerris remigis caloregon Calabrese, 1974b. Entomol. (Fig. 19) Gerris (Gerris) marginatus Say News 85: 27.

Reported from Idaho by Drake and Harris (1934), but were likely The large size of this transcontinental spe- misidentified. Not recorded from Idaho. cies (length 11.0-16.6 mm, width 3-4 mm) 264 Great Basin Naturalist Vol. 49, No. 2

Figs. 1-8. 1, Gerris remigis, dorsal view of head; 2, Metrobates trux infuscatus, dorsal view of head; 3, Limnoporus notabilis, ventral view of male abdominal apex; 4, Limnoporus notabilis, ventral view of female abdominal apex; 5, Gerris remigis, ventral view of male abdominal apex; 6, Gerris incurvatus, lateral view of head and pronotum; 7, Gerris buenoi, lateral view of head; S, Gerris incognitas, lateral view of head. April 1989 Biggam. Brusven: Idaho Water Striders 265

makes it easy to distinguish in the field from Gerris (Gerris) buenoi Kirkaldy other species of Gerris. This species is more Figs. 7, 9, 10

robust and shorter than members of the genus Gerris buenoi Kirkaldy, 1911. Entomol. News 22: 246. Limnoporus. It is the most abundant and Lectotype, macropterous female: Fort Collins, Colorado (CAS), designated by and Pol- widely distributed species of gerrid in the Menke

hemus ( 1973). state. Macropterous and apterous forms have been collected in Idaho. Brachypterous forms The broad, rectangular notch at the apex of occur rarely in the Pacific Northwest (Stone- sternum seven of the male and the female's dahl and Lattin 1982), but remain uncollected lack of spinelike, lateral prolongations on ter- in Idaho. Torre-Bueno (1917a), Scudder and gum six, combined with the presence of the Jamieson (1972), and Calabrese (1974a) de- anterolateral, pale, pronotal stripe and its scribed the nymphs. small size (length 6.5-8.2 mm, width 1.3-1.6 Geographic range. —Beported from the mm) separate this species from other Idaho 48 contiguous states, Canada, Mexico, and gerrids. Only macropterous and brachypter- Guatemala (Drake and Harris 1934). As de- ous forms have been collected in Idaho and fined here and by Stonedahl and Lattin the Pacific Northwest. (1982), G. remigis includes several forms from Geographic range. —Transcontinental in different regions of North America. Several of southern Canada and the northern United these forms have been described as distinct States from British Columbia east to New species and subspecies: Gerris orba Stal Jersey (Torre-Bueno 1911) and Massachusetts (1859) from San Francisco, California, and (Parshley 1916), southward into California G. remigis caloregon Calabrese (1974b) from (Polhemus and Chapman 1979) and Colorado California and Oregon. In addition, Gerris (Drake and Harris 1928). nijctalis Drake & Hottes (1925a) was de- Idaho records. —Specimens have been scribed from the U.S. National Park near Es- collected on ponds, lakes, and reservoirs in tes Park, Colorado, which is in the Rocky protected, vegetated areas in 15 counties: Mountains east of the Continental Divide. Bear Lake, Benewah, Blaine, Bonner, Boun- Michel (1962) reported a remigis -like form in dary, Canyon, Cassia, Custer, Franklin, Fre- Arizona, Texas, and Virginia. He claimed def- mont, Kootenai, Latah, Owyhee, Payette, inite differences in internal genitalia in east- and Valley. Adults have been collected from ern vs. western forms, but apparently without March through September, nymphs from examining type material or specimens from June through August. the type locality. Drake and Harris noted the occurrence of G. nijctalis in lakes at high ele- Gerris (Gerris) comatus Drake & Hottes vations in the Bocky Mountain regions, in- Figs. 17, 18

cluding Idaho. An intensive study will be nec- Gerris comatus Drake & Hottes, 1925a. Ohio J. Sei. 25: essary to determine the true taxonomic status 48. Holotype, macropterous male: Estes Park, Colorado, 27 August 1924, C. Drake and F. C. of these forms. In this paper we will call this J. Hottes. C.J. Drake (USNM). polymorphic species Gerris remigis Say, as Gerris comatus var. mickeli Drake & Hottes, 1925b. proposed by Stonedahl and Lattin (1982). Proc. Biol. Soc. of Washington 38: 72. Holotype, Idaho records. —Specimens have been brachypterous female: Rochester, Minnesota, 15 1922, C. E. Mickel. C. Drake (USNM). collected on the surfaces of ponds, lakes, June J. Gerris comatus mickeli Drake & Hottes, Drake and Har- reservoirs, creeks, and rivers in 33 counties: ris 1934. Annals of the Carnegie Museum 23: 193. Ada, Benewah, Bingham, Blaine, Boise, Bon- ner, Bonneville, Boundary, Butte, Camas, The females of this medium-sized species Canyon, Cassia, Custer, Elmore, Franklin, (length 7.3-9.3 mm, width 2.3-2.8 mm) are Fremont, Gooding, Jefferson, Kootenai, easily confused with those of G. marginatus Latah, Lemhi, Lewis, Lincoln, Madison, Say, as both lack the anterolateral stripes Minidoka, Nez Perce, Oneida, Payette, on the pronotum, with the exception of the Shoshone, Twin Falls, Valley, and Washing- mickeli variety listed above. Specimens of this ton. Adults have been collected every month morph have thus far all proven to be brachyp- of the year except November, and nymphs terous females. This striped morph may be have been collected from May through the result of a recessive gene surfacing be- November. cause of seasonal or environmental factors as it 266 Great Basin Naturalist Vol. 49, No. 2

Figs. 9-19. 9, Gerris buenoi, ventral view of male abdominal apex; 10, Gerris buenoi, ventral view of female abdominal apex; 11, Gerris gillettei, ventral view of female abdominal apex; 12, Gerris incognitus, ventral view of male abdominal apex; 13, gerris incognitus, lateral view of abdomen; 14, Gerris gillettei, lateral view of abdomen; 15, Gerris gillettei, dorsal view of abdomen; 16, Gerris marginatum, dorsal view of head and pronotum; 17, Gerris comatus, ventral view of male abdominal apex; 18, Gerris comatus, dorsal view of female abdominal apex; 19, Gerris marginatus, dorsal view of female abdominal apex. April 1989 Biggam, Brusven: Idaho Water Striders 267 did with a similar problem in Gerris incurva- Roemhild (1976) collected G. comatus in tus Drake & Hottes (Biggam and Stock 1988). Montana; all specimens were taken east of Electrophoretic analyses will probably re- the Continental Divide. Scudder (1971) listed solve this problem. Females of normal G. co- G. comatus from British Columbia, Canada, matus have the connexival spines short and which we have confirmed from specimens slightly curved medially and have apical tufts donated by the University of British Colum- of long, stiff hair; G. marginatus females usu- bia in Vancouver. Due to their close proxim- ally have straight connexival spines with api- ity, we have included it here and in our key as cal tufts of sparse, short hairs, similar in length a possible Idaho inhabitant. to the hair on the entire spine. Male G. coma- Idaho records. —None to date. tus have characteristic, circular tufts of long Gerris (Gerris) gillettei Lethierry Severin hair on the venter of abdominal segment & Figs. 11, 14, 15 seven on either side of the median keel. Ger- ris marginatus males lack these tufts, having Limnotrechus productus Uhler, 1895. Bull. Colorado Agrie. Expt. Sta. 31: 61. Holotype, female: Fort only short, apressed pubescence. Another Collins, Colorado (CSU). Preoccupied in Gerris species possibly in literature, confused some by productus Spinola, 1840. G. incurvatus Drake & Hottes, also lacks the Gerris gillettei Lethierry & Severin. 1896, Catalogue anterolateral, pronotal stripes but can now be general des Hemipteres 3: 60. New name for easily separated from G. comatus and G. mar- productus (Uhler). ginatus by pronotal pubescence. Dry, de- The presence of conspicuous patches of sil- greased specimens of G. incurvatus have only very pubescence on the tergal corners of the minute gold flecks, while G. comatus and abdomen in dry, degreased specimens will G. marginatus have golden flecks interrupted separate this species from the very similar by streaks or bands of reflective silvery setae. G. pingreensis Drake & Hottes. Callahan This is a new character previously unreported (1974) stated that females of G. gillettei are in literature. Apterous, brachypterous, and larger on the average (10.3 mm) than females macropterous forms are known. The nymphs of G. incognitas Drake & Hottes (9.1 mm). were described by Scudder and Jamieson Also, G. gillettei females are paler ventrally (1972). than those of G. incognitas. This color charac- Geographic range. —Recorded from the ter was confirmed by Stonedahl and Lattin Atlantic Ocean west to Montana, including (1982). The males are easily distinguished by New York, Iowa, South Dakota, Minnesota, the presence of tufts of long hair ventrally on Kansas, Missouri, Nebraska, Colorado, Indi- either side of the keel on abdominal segment ana, Michigan, Pennsylvania, Ohio, Illinois, seven in G. incognitos, and by the absence of New Jersey, Maryland, and Ontario (Drake such tufts in G. gillettei. Gerris gillettei is a and Harris 1934), British Columbia (Scudder medium-sized gerrid (length 8.5-11.5 mm, 1971), Quebec (Moore 1950), Alberta (Strick- width 1.7-2.3 mm). The anterolateral stripe land 1953), Manitoba and Saskatchewan on the pronotum is present. Macropterous (Brooks and Kelton 1967), and Arizona, Con- and apterous forms have been taken in the necticut, Florida, Oklahoma, New Hamp- state, but nymphs have not yet been de- shire, New Mexico, South Carolina, Virginia, scribed. Wisconsin, and Wyoming (Smith 1988). The Geographic range. —California, Colo- subspecies G. comatus mickeli Drake & Hot- rado, Montana, Oregon, Texas, Utah, and tes has been recorded from Minnesota (Drake Washington (Drake and Harris 1934), Wyo- and Hottes 1925b, as var. mickeli) and Oregon ming (Kuitert 1942), Nevada (Polhemus and and Colorado (Drake and Harris 1928). The Chapman 1979), and British Columbia (Smith Drake 6c Hottes subspecies, of which only 1988). Drake and Harris (1934) recorded G. brachypterous females are known, atypically pingreensis from the higher altitudes of has the anterolateral, pronotal stripe. Stone- Idaho. We have not seen true G. pingreensis dahl proposed that the G. comatus mickeli from Idaho and believe their specimens, recorded by Drake and Hottes from Oregon which we have been unable to locate, are was probably a misidentified G. incurvatus, probably G. gillettei Lethierry & Severin. as they found no G. comatus in Oregon Idaho records. —Specimens have been or Washington (personal communication). collected on lakes, ponds, and reservoirs in 268 Great Basin Naturalist Vol. 49, No. 2

11 counties: Ada, Blaine, Bonneville, Cassia, make this small species (length 7.6-10.7 mm, Custer, Fremont, Gooding, Lemhi, Oneida, width 2.3-2.5 mm) easy to identify. It can be Owyhee, and Twin Falls. Adults were col- confused with G. marginatus Say, especially lected from April through August, nymphs in the males, as the external genitalia are similar August. and both species lack the anterolateral, pronotal stripe. The new character, mentioned un- Gerris (Gerris) incognitas Drake & Hottes der G. comatus, has been consistent in over Figs. 8, 12, 13 60 confirmed specimens of G. marginatus and Gerris incognitos Drake & Hottes, 1925b. Proc. Biol. G. comatus- both species have two stripes or Soe. Wash. 38: 73. Holotype, macropterous male bands of silvery pubescence interrupting the (erroneously stated to be female): Kaslo, British uniform covering of golden flecks found on the Columbia (USNM: type missing). pronotum. This character has proven to be The longitudinal rows of long hairs lateral to consistent for both sexes with midwestern and the ventral keel of the male abdominal seg- eastern specimens examined by Gary Stone- ment eight, combined with the presence of dahl (New York) and Jack Lattin (Oregon) the anterolateral pronotal stripes, will easily (personal communication). Gerris incurva- separate this species from all other male ger- tus, on the other hand, has no silvery pu- rids of this size (length 6.7-11.0 mm, width bescence on the pronotum, only uniform, 2.5-2.9 mm) found in the state. Callahan short, golden pubescence characteristic of the (1974) stated that females of G. incognitus are subgenus Gerris. This character is im- smaller and darker ventrally than females of portant in separating rare and uncommon, G. gillettei Lethierry & Severin. Stonedahl brachypterous female forms of G. incurvatus and Lattin (1982) snowed the light, dorso- that have pronotal stripes, yet have the lateral, abdominal stripe extending the entire strongly incurved connexival spines. This rare length of the abdomen (Fig. 13). Macropter- form appears to be a genetic, seasonally in- ous and apterous specimens are known from duced morph (Biggam and Stock 1988). Idaho. Scudder and Jamieson (1972) and Macropterous and brachypterous forms have Spence and Scudder (1978) described the been collected in Idaho. Scudder and Jamie- nymphs. son (1972) described the nymphs. Geographic range. —California, Idaho, Geographic range. —California, Idaho, Montana, Oregon, Washington, British Co- Illinois, Montana, Oregon, Washington, and Harris lumbia, and Quebec (Drake and Harris 1934), British Columbia (Drake and 1934), (Kuitert and Ne- Colorado and Wyoming (Kuitert 1942), Ne- Texas and Wyoming 1942), and Chapman 1979). Al- vada (Polhemus and Chapman 1979), and Al- vada (Polhemus and Harris (1934) listed this berta, Manitoba, Ontario, and Saskatchewan though Drake species from Illinois, it was not found in (Smith 1988). Gould 1936), Missouri Idaho records. —This species has been Indiana (Deay and Wisconsin (Hilsenhoff collected on ponds, lakes, and reservoirs in (Froeschner 1962), (Osborn and Drake 1915). 20 counties: Bear Lake, Benewah, Blaine, 1986), or Ohio Specimens have been Bonner, Bonneville, Boundary, Caribou, Idaho records. — ponds, lakes, and reservoirs in 23 Cassia, Clearwater, Custer, Fremont, Good- collected on counties: Ada, Adams, Bannock, Benewah, ing, Idaho, Latah, Lemhi, Owyhee, Sho- Blaine, Bonner, Camas, Canyon, Cassia, shone, Teton, Twin Falls, and Valley. Adults Fremont, Gooding, Idaho, Koote- were collected from March through Septem- Franklin, nai, Latah, Lemhi, Lewis, Madison, Nez ber, nymphs from May through August. Perce, Owyhee, Shoshone, Twin Falls, and Gerris (Gerris) incurvatus Drake & Hottes Washington. Adults have been collected from Fig. 6 March through October, nymphs from May Gerris incurvatus Drake & Hottes, 1925b. Proc. Biol. through August. Soe. Wash. 38: 72. Holotype, male: Bozeman, Gerris (Gerris) marginatus Say Montana. C J. Drake (USNM). Figs. 16, 19 anterolateral stripes on the The lack of pale, Gerris marginatus Say, 1832. Descriptions of new species pronotum and the strongly incurved lateral of heteropterous Hemiptera of North America, spines of the female abdominal segment seven New Harmony, Indiana, p. 36 (Fitch reprint, April 1989 Biggam, Brusven: Idaho Water Striders 269

1858. Trans. New York State Agric. Soe. 17). Page This species is easily confused with G. 35 in The complete writings of Thomas Say on the gillettei Lethierry & Severin. Although G. entomology of North America. J. L. LeConte, ed. pingreensis and G. gillettei are readily sepa- Vol. I. 362 pp. Bailliere Brothers, New York. (Types destroyed.) rated by the conspicuous silvery patches of setae at the dorsolateral tergal apices on G. This medium-sized water strider (length gillettei and their absence on G. pingreensis, 8.0-10.5 mm, width 2.3-2.6 mm) reportedly confusion between the two species may be the lacks the anterolateral stripe on the pronotum result of grease or liquid preservatives that that is common in most individuals of G. in- conceal these silvery hairs. Gerris pingreensis curvatus Drake & Hottes and G. comatus is similar in size to G. buenoi Kirkaldv (length Drake & Hottes. However, since the latter 9.0-10.00 mm, width 2.0-2.5 mm). Maerop- two species include some brachypterous indi- terous and apterous forms are known for this viduals with pronotal stripes, similar individ- species (Drake and Hottes 1925a). Scudder uals of G. marginatus may yet be discovered. and Jamieson (1972) and Spence and Scudder It is easily separated from G. incurvatus by (1978) described the nymphs. the presence of two longitudinal bands of lon- Geographic range. —Streams and lakes of ger, silvery pubescence on the pronotum. the higher altitudes of Montana, Colorado, This character also occurs in G. comatus; Idaho, and Alberta, (Drake and Harris 1934, however, the males of G. comatus have circu- Strickland 1953), and British Columbia (Scud- lar tufts of hair ventrally on abdominal ster- der 1971). Roemhild (1976) also records this num eight. Males of G. marginatus do not species from Montana west of the Continental have this character. The females of G. mar- Divide. Alberta, Saskatchewan, and Mani- ginatus have the connexival spines rather toba (Brooks and Kelton 1967), Quebec straight, slightly upturned, and without (Moore 1950), Yukon-Northwest Territories strong setae at the tips. Females of G. coma- (Scudder 1971), and Alaska (Smith 1988). tus have the spines curving slightly inward Idaho records. —The Idaho records of and tipped with strong setae. Drake and Harris (1934) are probably incor- Geographic range. —Drake and Harris rect and are believed to pertain to G. gillettei (1934) reported this species occurring in every Lethierry & Severin. We have not collected state in the United States and in Canada, this species in Idaho, nor have we been able to Mexico, and Brazil. As mentioned in the biol- locate the Drake and Harris specimens to con- ogy section, pertinent literature concerning firm its presence in Idaho. We include it here this species is confusing, and we suspect that as possibly inhabiting the higher elevations two or more species may have been involved along the eastern and northern boundaries of in the reportings of earlier workers (Drake the state. and Harris 1934). This may be true of the Torre-Bueno (1917b) paper on the immature Genus Limnoporus Stal stages and life history of G. marginatus. Limnoporus Stal, 1868. Ofvers. K. Vet.—Akad. Forh Stonedahl and Lattin (1982) believed the 25: 395. Type species: Gerris rufoscutellatus Oregon and Washington records of Drake and Latreille, 1807 monotypic. Harris (1934) to be G. incurvatus, which ap- Andersen (1975) elevated this subgenus of parently replaces G. marginatus in the West. Gerris to generic status. The proportions of Roemhild (1976) recorded G. marginatus the antennal segments serve to separate it from Montana. From his identified material, from the closely related Gerris spp. Four spe- only a single specimen was recorded west of cies are recorded from the Americas, all the Continental Divide. The close proximity Nearctic. Only one species is recorded from of this species to Idaho prompts us to include Idaho. it in our as a possible inhabitant of the key Limnoporus notabilis (Drake & Hottes) state. Figs. 3, 4 Idaho records. —None. Gerris (Limnoporous) [sic] notablis [sic] Drake & Hottes, 1925a. Ohio. Sci. 25: 46. Holotype, maeropter- Gerris (Gerris) pingreensis Drake & Hottes J. ous male: Pingree Park, Colorado. C J. Drake

Gerris pingreensis Drake & Hottes, 1925a. Ohio J. Sei. (USNM). 25: 49. Holotype, maeropterous male: Pingree Gerris notabilis Drake & Hottes, 1925b. Proc. Biol. Soc.

Park, Colorado. C. J. Drake (USNM). ofWashington38:73. 270 Great Basin Naturalist Vol. 49, No. 2

This is the largest gerrid in the state (length Genus Metrobates Uhler

14.4-20.0 mm, width 2.0-2.5 mm). Its long, Metrobates Uhler, 1871b. Boston Soc. Nat. Hist. 14: 108. slender body and legs make it distinctive and Type species: Metrobates hesperius Uhler, 1871b, easily separated from members of the genus monotypic. Trepobatopsis Champion, 1898. Biologia Centrali Ameri- Gerris. Sternum six of the males is not secon- cana, Rhynchota 2: 157. darily notched as in Gerris males. The very similar L. dissortis Drake & Harris, which Members of this genus have short, broad, occurs in the Midwest up to the Rockies, may dorsoventrally flattened abdomens. The sec- be confused with notabilis because of the sim- ond and third antennal segments of the male distally. is grey with ilar color pattern. However, L. dissortis is a are swollen The body smaller species with shorter legs than L. nota- black markings. These bugs prefer large rivers with currents. Worldwide there are bilis. The antennal segment ratios as de- moderate scribed by Drake and Harris (1934) appear to 14 recognized species with four subspecies. be the best character for separating L. nota- Five species occur in the United States; one its occur in Idaho. bilis and L. dissortis, the latter being reported species and subspecies The from British Columbia by Scudder (1977). genus was last revised by Anderson (1932) and The occurrence of hybrids between these two Drake and Harris (1932). species in British Columbia (Spence and Mad- Metrobates trux infuscatus Usinger dison 1986) further complicates distribution Fig. 2 records. Idaho L. notabilis have the third and Metrobates trux infuscatus Usinger, 1953. Pan-Pac. En- fourth antennal segments subequal and each tomol. 29: 178-179. Holotype, male: Putah Cr., shorter than the second segment. Limnopo- Davis, California (CAS). rus dissortis has the second and fourth seg- The short, broad, dorsoventrally flattened ments subequal, each longer than the third abdomen (length 4.0-4.6 mm) and the grey segment. Only the macropterous form is color with black markings, combined with the known in Idaho and the Pacific Northwest. extremely long legs, make this unique species Scudder and Jamieson (1972) described the the most easily identified gerrid in Idaho. nymphs. Apterous and rarely macropterous forms have Geographic range. — California, Colo- been collected in Idaho. Nymphs of this spe- rado, Idaho, Iowa, Oregon, Montana, Utah, cies have not been described. Washington, Wyoming, and British Columbia Geographic range. —Central and north- (Drake and Harris 1934), Colorado (Drake ern California (Polhemus and Chapman 1979, and Harris 1935), Arizona and South Dakota Usinger 1953), Idaho, Washington, and Wyo- (Kuitert 1942), Alberta (Brooks and Kelton ming (Polhemus and Chapman 1979), Oregon 1967), and New Mexico (Smith 1988). Drake (Stonedahl and Lattin 1982), and New Mexico and Harris (1930) list this species as western and Arizona (Smith 1988). and occurring as far east as Iowa. Smith (1988) listed the subspecies M. trux Idaho records. —This species has been trux (Torre-Bueno) from Idaho as well as collected on ponds, lakes, reservoirs, and Arizona, California, Colorado, Kansas, New slower moving streams and rivers in 30 Mexico, and Texas. Drake and Harris (1932) counties: Ada, Adams, Bear Lake, Benewah, stated that the second antennal segment of the Blaine, Boise, Bonner, Bonneville, Boun- Texas specimens was, at least in part, yellow- dary, Butte, Camas, Canyon, Caribou, Cas- ish brown, unlike those of Oregon and Idaho sia, Clark, Custer, Elmore, Franklin, Fre- specimens. Usinger (1953) described M. trux mont, Gem, Gooding, Idaho, Kootenai, infuscatus from specimens originally deter- Latah, Nez Perce, Owyhee, Payette, Sho- mined by H. B. Hungerford and L. D. Ander- shone, Valley, and Washington. Adults were son as "M. trux Bueno," noting the darker collected from March through October, markings of the upper surface as being more nymphs in August. extensive than the typical form described from Colorado and recorded from Texas, Kan- Subfamily Trepobatinae sas, Arizona, and, apparently erroneously, Two of the 13 genera in this subfamily occur Oregon and Idaho. Based on our examination in North America. Only one is found in Idaho. of available Idaho material and Polhemus and April 1989 Biggam, Brusven: Idaho Water Striders 271

Chapman (1979), we suggest that M. trux Literature Cited specimens collected and identified from Ore- Andersen, N. M 1973. Seasonal polymorphism and de- gon and Idaho prior to Usinger's description of velopmental changes in organs of flight and repro- (1953) are probably the M. trux infuscatus duction in bivoltine pondskaters. Entomol. latter subspecies, despite confusion in the lit- Scand. 4: 1-20. erature. The deletion of Idaho as a locality for 1975. The Limnogonas and Neogerris of the Old M. trux trux (Torre-Bueno) appears advis- World with character analysis and a reclassification of the Gerrinae. Entomol. Scand., Supp. 7. 96 able, leaving Arizona, (southern) California, pp. 1982. The semiaquatic bugs (Hemiptera; Gerro- Colorado, Kansas, New Mexico, and Texas as morpha)—phylogeny, adaptations, biogeography the more likely distribution of this subspecies. and classification. Entomograph Vol. 3. Scandina- Stonedahl and Lattin (1982) contend that M. vian Science Press Ltd., Klampenborg-Denmark. trux infuscatus Usinger is the only subspecies 455 pp.

Andersen. N . and T Polhemus 1976. Water- occurring in the Pacific Northwest. M J striders (Hemiptera: Gerridae, Veliidae, etc.). Idaho RECORDS. —This unique species has Pages 187-224 in L. Cheng, ed.. Marine insects. been collected on major rivers and creeks in North Holland Publishing Co. , New York. moderate currents in four counties: Benewah, Anderson. L D 1932. A monograph of the genus Metro- Clearwater, Latah, and Owyhee. Adults have bates. University of Kansas Sci. Bull. 29:297-311. been collected in August and September, BEAL, F E L 1918. Food habits of the swallows. USDA Bull. 619. nymphs in July and August. Bicgam, R. C, and M. W. Stock 1988. Pronotal stripes and wing length in Gerris incurvatus Drake and Acknowledgments Hottes. Pan-Pac. Entomol. 64(4): 359-363. Bobb. M L 1951. The life history of Gerris canaliculatus

The authors express their gratitude to the Say in Virginia. Virginia J. Sci. 2: 102-108. following for their determinations, searches, 1974. The aquatic and semi-aquatic Hemiptera of Virginia. Virginia Polytechnic Inst., Res. Div., loans, and other taxonomic assistance: Edwin Bull. 87. 196 pp. F. Cook and Jeffrey D. Hahn, University of Brinkhurst. R O 1959. Alary polymorphism in the Ger- Minnesota; B. Spence, University of Al- John roidea. J. Anim. Ecol. 28: 211-230. berta; George B. Boemhild and Mike A. Ivie, 1960. Studies on the functional morphology of Montana State University; John K. Bouse- Gerris najas De Geer. Proc. Zool. Soc. Lond. 133: 531-559. man, Illinois Department of Energy and Nat- 1961. Alary polymorphism in the Gerroidea. Ver. ural Besources, Champaign, Illinois; Richard Int. Vereinigung fur Theoretische und Ange- C. Froeschner, U.S. National Musuem of wandte Limnologie 14: 978-982. Natural History, Smithsonian Institution; 1963. Observations on wing-polymorphism in Paul Kittle, Southeast Missouri State Univer- the Heteroptera. Proc. R. Entomol. Soc. London (A)38: 15-22. sity; Robert Lewis, Iowa State University; Brooks, A. R.. and L. A Kelton. 1967. Aquatic and semi- G. G. E. Scudder, University of British aquatic Heteroptera of Alberta, Saskatchewan and Columbia; George W. Byers, University of Manitoba. Mem. Entomol. Soc. Canada, No. 51. Kansas; Charles Baker, Boise State Univer- 92 pp. sity; William H. Clark, College of Idaho- Calabrese. D M 1974a. Keys to the adults and nymphs Caldwell; Al Allan, Boise, Idaho; Larry B. of the species of Gerris Fabricius occurring in Connecticut. Pages 227-266 in Mem. Connecti- Schoenike, Island Park, Idaho; Charles E. cut Entomol. Soc, 25th anniv. ed. Hornig, Bedmond, Washington; Karla M. 1974b. Population and subspecific variation in Schwartz (now Beynolds), Kuna, Idaho; Gerris remigis Say. Entomol. News 85: 27-28, 30. Bobert L. Gillespie, Montana Department of 1977. The habitats of Gerris F. (Hemiptera: Het- Agriculture, Helena; Daniel T. Wade, eroptera: Gerridae) in Connecticut. Ann. Ento- mol. Soc. Amer. 70: 977-983. Boston, Massachusetts; John T. Polhemus,

Calabrese, D M . and P Tallerico 1982. Gerris University of Colorado Museum; Gary M. remigis Say in a unique winter environment Stonedahl, American Museum of Natural His- (Hemiptera-Heteroptera: Gerridae). Entomol. tory—N.Y.; John D. Lattin, Oregon State News 93: 152-154. Callahan. R. 1974. Observations on Gerris incogni- University; William F. Barr, James B. John- J. tas and Gerris gillettei. Proc. Entomol. Soc. son, Fred W. Babe, Frank W. Merickel, Paul Washington 76: 15-21. E. Blom, Paul Johnson, and Norman A. J. Chenc, L 1967a. Studies on the biology of the Gerridae.

Bowers, University of Idaho; and Cheryl L. I. Observations on the feeding of Limnogonas fos- Noble, Flagstaff, Arizona, for the illustrations. sarum(F.). Entomol. Mon. Mag. 102: 121-128. 272 Great Basin Naturalist Vol. 49, No. 2

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