Our l.ivin\i Rt'M}nrccs — Invi'rti'hivrfs 



161 



Insects are the most diverse grtnip of organ- 

 isms (Wheeler 1990); potentially they are 

 highly indicative of environmental change 

 through close adaptation to their environment: 

 they represent the majority of links in the com- 

 munity foodchain; and they likely have the 

 largest biomass of the terrestrial animals 

 (Holden 1989). Thus, knowledge about them is 

 fundamental to studying the environment. 



The 34 orders of insects have 90.968 

 described species and an estimated 72,500-i- 

 undescribed species in 653 families and 12,578 

 genera (Arnett 1985; Kosztarab and Schaefer 

 1990) in America north of Mexico. Of the 

 described species 71,931 are in the orders 

 Coleoptera (beetles, 23,640), Diptera (tlies, 

 19,562), Hymenoptera (ants, bees, wasps, and 

 sawflies, 17,429), and Lepidoptera (moths and 

 butterflies, 11,300). Undescribed species are 

 distributed mainly among Homoptera (aphids. 

 leatlioppers, scale insects, and allies, 4,334). 

 Coleoptera (2,627), Diptera (41,622), 

 Hymenoptera ( 1 8,57 1 ), and Lepidoptera (2.700; 

 Kosztarab and Schaefer 1990). 



Some aspects of the immature stages of 

 8,668 species are known (Kosztarab and 

 Schaefer 1990); however, very few are fully 

 known (i.e., documented with voucher speci- 

 mens and publications with illustrations of 

 eggs, each larval instar, and pupae). Detailed 

 knowledge of the immature stages is important 

 because insects often are present as adults for a 

 short period during the year, but are present as 

 eggs, larvae, or pupae during most of the year. 



Taxonomic literature useful for identifying 

 described species is available for less than 30% 

 of them in the adult stage. No major order has 

 been subjected to revisionary study at the spe- 

 cific level, and only two such projects are under 

 way, Lepidoptera (Dominick 1971+) and 

 Diptera (Griffiths 1980+). Some smaller orders, 

 some families, and many genera have been 

 revised for North America (e.g., bethylid wasps 

 [Evans 1978], cerambycid beetles [Linsley and 

 Chemsak 1961-84], chrysidid wasps [Bohail 

 and Kimsey 1982], dragontlies [Odonata; 

 Needham and Westfall 1955], grasshoppers 

 [Orthoptera; Otte 1981, 1983], lady beetles 

 [Gordon 1985], springtails [Collembola; 

 Christiansen and Bellinger 1980-81], thrips of 

 Illinois [Thysanoptera; Stannard 1968], and 

 beetles of the Pacific Northwest [Hatch 1953- 

 71J). Several family or ordinal groups have been 

 revised for Canada and the northern United 

 States. Diptera (Stone et al. 1965; Systematic 

 Entomology Laboratory, U.S. Department of 

 Agriculture, unpublished), Heteroptera (Henry 

 and Froeschner 1988), and Hymenoptera 

 (Krombein et al. 1979) have been cataloged. 

 The Lepidoptera have a checklist (Hodges et al. 



1983). A nomenclatorial data base (BIOTA, 

 Biosystematic Information on Terrestrial 

 Arthropods, available via Internet or on CD- 

 ROM) for ten-estrial arthropods (less Crustacea) 

 is being developed and coordinated by the 

 Systematic Entomology Laboratory, USDA 

 (Hodges 1994). 



For all major orders much revisionary work 

 is needed to define and discriminate anK)ng 

 species, genera, and higher taxa in a broad sense 

 and with recognition of variation in nearly all 

 characters. From these works field guides and 

 identification manuals must be developed. 

 Literature for lay workers and students should 

 provide identification to the species level by 

 state or region as this information is necessary 

 for conducting surveys (Keys to British 

 Insects — a continuing publication series of the 

 Royal Entomological Society, London — is an 

 excellent example). 



Several states have programs to document 

 their fauna with publications and voucher mate- 

 rial: California Insect Survey, Florida State 

 Collection of Arthropods, Illinois Natural 

 History Survey, New York State Natural History 

 Survey, and Insects of Virginia, Blacksburg. 

 Few state faunal lists exist; the few that do are 

 outdated or limited: all insects of New York 

 (Leonard 1926) and North Carolina (Brimley 

 1938, 1942; Wray 1950, 1967); Lepidoptera of 

 Florida (Kimble 1965), Maine (Brower 1974, 

 1983, 1984), New York (Forbes 1923. 1948, 

 1954, I960), and Pennsylvania (Tietz 1952). 

 Checklists or faunal lists of Odonata exist for 39 

 states and provinces (Westfall 1984). Surveys 

 by county are under way for Kentucky 

 (Lepidoptera, University of Louisville, unpub- 

 lished data), Maryland (scattered orders and 

 families, Maryland Entomological Society), 

 Missouri (moths, J.R. Heitzman, unpublished 

 data), Ohio (Lepidoptera, Ohio Lepidopterists; 

 Metzler 1980; Iftner et al. 1992; Rings et al. 

 1992; unpublished data), and the western 

 United States (butterflies; Stanford and Opler 

 1993). Extensive data have been collected on 

 the distribution of Alaskan butterflies by the 

 Alaska Lepidoptera Survey (Philip, University 

 of Alaska, unpublished data). 



No site in North America has been fully sur- 

 veyed for all insects; however, the Mount Desert 

 Island, Maine, survey (Procter 1946) was an 

 early attempt to do so. Of an estimated 6,000 

 species, 3,400 have been reported from the H.J. 

 Andrews Experimental Forest, Oregon (Parsons 

 et al. 1991). Craters of the Moon National 

 Monument. Idaho (Homing and Barr 1970); 

 Deep Creek in San Bernardino County, 

 California (S.I. Frommer, University of 

 Califomia, Riverside, unpublished data): and 

 Pawnee Grasslands, Colorado (Kumar et al. 



Diversity and 

 Abundance of 

 Insects 



by 



Ronald W. Hodges 



U.S. Department of 



Agriculture Systematic 



Entomology Laboratory 



Leaf- footed bug (Thasus sp.). 



Hi 



