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 Follow this and additional works at: https://scholarsarchive.byu.edu/gbn 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;