Diversity and Abundance of Insects

Diversity and Abundance of Insects
		by *Ronald W. Hodges* U.S. Department of Agriculture Systematic Entomology Laboratory
Insects are the most diverse group of organisms (Wheeler 1990); potentially they are highly indicative of environmental change through close adaptation to their environment; they represent the majority of links in the community 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+ 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 (flies, 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, leafhoppers, scale insects, and allies, 4,334), Coleoptera (2,627), Diptera (41,622), Hymenoptera (18,571), 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 specimens 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.

Leaf-footed bug (Thasus sp.). Courtesy G. Zolnerowich

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 specific 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 [Bohart and Kimsey 1982], dragonflies [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 1953-71]). 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 terrestrial 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 among 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).

Mantidfly (Mantispa interrupta). Courtesy J.R. Bruschwein

Several states have programs to document their fauna with publications and voucher material: 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, 1960), 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, unpublished 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 surveyed 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 (Horning and Barr 1970); Deep Creek in San Bernardino County, California (S.I. Frommer, University of California, Riverside, unpublished data); and Pawnee Grasslands, Colorado (Kumar et al. 1976) have been intensively surveyed for insects but none of the surveys approaches completion. A constant problem has been the inability to identify all the numerous taxa.

Robber fly (Diogmites symmachus). Courtesy C.E. Williams

Sampling for taxa, except for aquatics, is based mainly on adults; results are highly variable, depending on the competency of the samplers, knowledge of habits of organisms, weather during sampling periods, and phases of the moon and wavelength of light (for those species attracted to light). With exceptions (aquatic insects; Merritt et al. 1984), sampling techniques to estimate species diversity within an area have not been developed or are preliminary for limited taxa.

Identification of adults within large orders depends on highly trained, experienced taxonomists who have access to good collections and libraries; very few taxonomists exist relative to the number of taxa. Identifications in collections must be held suspect unless the taxa have been revised in contemporary terms and the specimens studied and vouchered by the revisor (Hodges 1976) or other specialist.

Spurge hawkmoth (Hyles euphorbiae). Courtesy J. Heraty

Individuals capable and willing to provide authoritative identifications are becoming fewer each year. Many have retired or could retire. There has been a significant redirection of systematists from basic revisionary work to other research areas. Nearly 30% fewer persons are entering the field because the likelihood of obtaining a position upon completion of training is extremely poor (Lutz 1994). Technical and monetary support for systematists and curators always has been limited and is becoming more restricted.

Collections vary in size from small private collections to the 30+ million specimens in the National Insect Collection in the National Museum of Natural History. Many state universities, particularly in the Midwest and on the West Coast, have collections of 1+ million specimens, as do several private and public institutions. Despite this large number, many species are represented by few specimens and almost none with comprehensive representation by county and by state.

Tiger beetle (Cicindela hirticollis). Courtesy N. Erwin

Surveys of many taxa are possible but require individuals to initiate them; sufficient taxonomic literature and research to enable recognition of taxa; curatorial support for preparing, sorting, and identifying specimens and potential supervision of the surveys; and adequate collection and library facilities for species recognition and permanent storage of voucher specimens.
These comments are meant to provide perspective on the status of systematic entomology and thus the role insects may have in the work of the National Biological Service.
		For further information: Ronald W. Hodges Systematic Entomology Laboratory, USDA c/o National Museum of Natural History, MRC-168 Washington, DC 20560

References
Arnett, R.H. 1985. American insects: a handbook of the insects of America north of Mexico. Van Nostrand Reinhold Co., New York. 850 pp. Bohart, R.M., and S.S. Kimsey. 1982. A synopsis of the Chrysididae in America north of Mexico. Memoirs of the American Entomological Institute 33:1-266. Brimley, C.S. 1938. The insects of North Carolina. North Carolina Department of Agriculture, Raleigh. 560 pp. Brimley, C.S. 1942. Supplement to insects of North Carolina. North Carolina Department of Agriculture, Raleigh. 39 pp. Brower, A.E. 1974. A list of the Lepidoptera of Maine--Part 1, the macrolepidoptera. Life Sciences and Agriculture Experiment Station Tech. Bull. 66:1-136. Brower, A.E. 1983. A list of the Lepidoptera of Maine--Part 2. Maine Department of Conservation and the Department of Entomology Tech. Bull. 109:1-60. Brower, A.E. 1984. A list of the Lepidoptera of Maine--Part 2 (concluded). Maine Department of Conservation and the Department of Entomology Tech. Bull. 114:1-70. Christiansen, K.A., and P. Bellinger. 1980-81. The Collembola of North America north of the Rio Grande, a taxonomic analysis. Grinnell College, Grinnell, IA. 4 vols. Dominick, R.B., ed. 1971+. The moths of America north of Mexico, including Greenland. The Wedge Entomological Research Foundation, Washington, DC. [19 parts] Evans, H.E. 1978. The Bethylidae of America north of Mexico. Memoirs of the American Entomological Institute 27:1-332. Forbes, W.T.M. 1923. The Lepidoptera of New York and neighboring states. Part 1. Cornell University Agricultural Experiment Station Memoir 68:1-729. Forbes, W.T.M. 1948. The Lepidoptera of New York and neighboring states. Part 2. Cornell University Agricultural Experiment Station Memoir 274:1-263. Forbes, W.T.M. 1954. The Lepidoptera of New York and neighboring states. Part 3. Cornell University Agricultural Experiment Station Memoir 329:1-433. Forbes, W.T.M. 1960. The Lepidoptera of New York and neighboring states. Part 4. Cornell University Agricultural Experiment Station Memoir 371:1-188. Gordon, R.D. 1985. The Coccinellidae (Coleoptera) of America north of Mexico. Journal of the New York Entomological Society 93(1):1-912. Griffiths, C.D.G., ed. 1980+. Flies of the Nearctic Region. E. Schweizerbart'sche Verlagsbuchhandlung. Stuttgart. [19 parts] Hatch, M.H. 1953-71. The beetles of the Pacific Northwest. Part 1: Introduction and Adephaga, 340 pp.; Part 2: Staphyliniformia, 384 pp.; Part 3: Pselaphidae and Diversicornia I, 503 pp.; Part 4: Macrodactyles, Palpicornes, and Heteromera, 268 pp.; Part 5: Rhipiceroidea, Sternoxi, Phylophaga, Rhynchophora, and Lamellicornia, 662 pp. University of Washington Press, Seattle. Henry, T.J., and R.C. Froeschner. 1988. Catalog of the Heteroptera, or true bugs, of Canada and the continental United States. E.J. Brill, Leiden, The Netherlands. 958 pp. Hodges, R.W. 1976. Presidential address 1976--what insects can we identify? Journal of the Lepidopterists' Society 30:245-251. Hodges, R.W. 1994. BIOTA. Association of Systematics Collection Newsletter 21(6):72. Hodges, R.W., et al., eds. 1983. Check list of the Lepidoptera of America north of Mexico. E.W. Classey Ltd. and the Wedge Entomological Research Foundation, London, England. 284 pp. Holden, C. 1989. Entomologists wane as insects wax. Science 246:754-756. Horning, D.S., Jr., and W.F. Barr. 1970. Insects of Craters of the Moon National Monument, Idaho. University of Idaho College of Agriculture Miscellaneous Series 8:1-118.	Iftner, D.C., J.A. Shuey, and J.V. Calhoun. 1992. Butterflies and skippers of Ohio. Ohio Biological Survey Bull. 9(1):1-212. Kimble, C.P. 1965. Lepidoptera of Florida. Arthropods of Florida and Neighboring Land Areas 1:1-363. Kosztarab, M., and C.W. Schaefer. 1990. Conclusions. Pages 241-247 in M. Kosztarab and C.W. Schaefer, eds. Systematics of the North American insects and arachnids: status and needs. Virginia Agricultural Experiment Station Information Series 90-1. Krombein, K.V., P.D. Hurd, Jr., D.R. Smith, and B.D. Burks. 1979. Catalog of the Hymenoptera in America north of Mexico. Smithsonian Institution Press, Washington, DC. 2,735 pp. Kumar, R., R.J. Lavigne, J.E. Lloyd, and R.E. Pfadt. 1976. Insects of the Central Plains Experimental Range Pawnee National Grassland. University of Wyoming Agricultural Experiment Station Science Monograph 32:1-74. Leonard, M.D., ed. 1926. A list of the insects of New York with a list of the spiders and certain other allied groups. Cornell University Agricultural Experiment Station Memoir 101:1-1,121. Linsley, E.G., and J.A. Chemsak. 1961-84. The Cerambycidae of North America. Parts 1-7. University of California Press, Berkeley. Lutz, D. 1994. More than stamp collecting. American Scientist 82(2):120-121. Merritt, R.W., K.W. Cummins, and V.H. Resch. 1984. Collecting, sampling, and rearing methods for aquatic insects. Pages 11-26 in R.W. Merritt and K.W. Cummins, eds. An introduction to the aquatic insects of North America. Kendall/Hunt, Dubuque, IA. Metzler, E.H. 1980. Annotated checklist and distribution maps of the royal moths and giant silkworm moths (Lepidoptera: Saturniidae) in Ohio. Ohio Biological Survey Biological Notes 14:1-10. Needham, J.G., and M.J. Westfall, Jr. 1955. A manual of the dragonflies of North America (Anisoptera). University of California Press, Berkeley. 615 pp. Otte, D. 1981. North American grasshoppers. Vol. 1. Gomphocerinae and Acridinae. Harvard University Press, Cambridge, MA. 275 pp. Otte, D. 1983. North American grasshoppers. Vol. 2. Oediodinae. Harvard University Press, Cambridge, MA. 366 pp. Parsons, G.R., G. Cassis, A.R. Moldenke, J.D. Lattin, et al. 1991. Invertebrates of the H.J. Andrews Experimental Forest, Western Cascade Range, Oregon. V: An annotated list of insects and other arthropods. U.S. Forest Service General Tech. Rep. 290:1-168. Procter, W. 1946. Biological survey of the Mount Desert Region. Part 7. Wistar Institute, Philadelphia, PA. 566 pp. Rings, R.W., E. H. Metzler, F. J. Arnold, and D.H. Harris. 1992. The owlet moths of Ohio, order Lepidoptera family Noctuidae. Ohio Biological Survey Bull. 9(2):1-222. Stanford, R.E., and P.A. Opler. 1993. Atlas of western U.S.A. butterflies, including adjacent parts of Canada and Mexico. Published by authors, Denver, CO. 275 pp. Stannard, L.J. 1968. The thrips, or Thysanoptera, of Illinois. Illinois Biological Monographs 25:1-200. Stone, A., C.W. Sabrosky, W.W. Wirth, et al. 1965. A catalog of the Diptera of America north of Mexico. Agriculture Handbook 276:1-1696. Tietz, H.M. 1952. The Lepidoptera of Pennsylvania. Pennsylvania State College, School of Agriculture, Agriculture Experiment Station. State College, PA. 194 pp. Westfall, M.J., Jr. 1984. Odonata. Pages 126-176 in R.W. Merritt and K.W. Cummins, eds. An introduction to the aquatic insects of North America. Kendall/Hunt, Dubuque, IA. Wheeler, Q.D. 1990. Insect diversity and cladistic constraints. Annals of the Entomological Society of America 83(6):1031-1047. Wray, D.L. 1950. Insects of North Carolina: second supplement. North Carolina Department of Agriculture, Raleigh. 59 pp. Wray, D.L. 1967. Insects of North Carolina: third supplement. North Carolina Department of Agriculture, Raleigh. 181 pp.

References

Arnett, R.H. 1985. American insects: a handbook of the insects of America north of Mexico. Van Nostrand Reinhold Co., New York. 850 pp.

Bohart, R.M., and S.S. Kimsey. 1982. A synopsis of the Chrysididae in America north of Mexico. Memoirs of the American Entomological Institute 33:1-266.

Brimley, C.S. 1938. The insects of North Carolina. North Carolina Department of Agriculture, Raleigh. 560 pp.

Brimley, C.S. 1942. Supplement to insects of North Carolina. North Carolina Department of Agriculture, Raleigh. 39 pp.

Brower, A.E. 1974. A list of the Lepidoptera of Maine--Part 1, the macrolepidoptera. Life Sciences and Agriculture Experiment Station Tech. Bull. 66:1-136.

Brower, A.E. 1983. A list of the Lepidoptera of Maine--Part 2. Maine Department of Conservation and the Department of Entomology Tech. Bull. 109:1-60.

Brower, A.E. 1984. A list of the Lepidoptera of Maine--Part 2 (concluded). Maine Department of Conservation and the Department of Entomology Tech. Bull. 114:1-70.

Christiansen, K.A., and P. Bellinger. 1980-81. The Collembola of North America north of the Rio Grande, a taxonomic analysis. Grinnell College, Grinnell, IA. 4 vols.

Dominick, R.B., ed. 1971+. The moths of America north of Mexico, including Greenland. The Wedge Entomological Research Foundation, Washington, DC. [19 parts]

Evans, H.E. 1978. The Bethylidae of America north of Mexico. Memoirs of the American Entomological Institute 27:1-332.

Forbes, W.T.M. 1923. The Lepidoptera of New York and neighboring states. Part 1. Cornell University Agricultural Experiment Station Memoir 68:1-729.

Forbes, W.T.M. 1948. The Lepidoptera of New York and neighboring states. Part 2. Cornell University Agricultural Experiment Station Memoir 274:1-263.

Forbes, W.T.M. 1954. The Lepidoptera of New York and neighboring states. Part 3. Cornell University Agricultural Experiment Station Memoir 329:1-433.

Forbes, W.T.M. 1960. The Lepidoptera of New York and neighboring states. Part 4. Cornell University Agricultural Experiment Station Memoir 371:1-188.

Gordon, R.D. 1985. The Coccinellidae (Coleoptera) of America north of Mexico. Journal of the New York Entomological Society 93(1):1-912.

Griffiths, C.D.G., ed. 1980+. Flies of the Nearctic Region. E. Schweizerbart'sche Verlagsbuchhandlung. Stuttgart. [19 parts]

Hatch, M.H. 1953-71. The beetles of the Pacific Northwest. Part 1: Introduction and Adephaga, 340 pp.; Part 2: Staphyliniformia, 384 pp.; Part 3: Pselaphidae and Diversicornia I, 503 pp.; Part 4: Macrodactyles, Palpicornes, and Heteromera, 268 pp.; Part 5: Rhipiceroidea, Sternoxi, Phylophaga, Rhynchophora, and Lamellicornia, 662 pp. University of Washington Press, Seattle.

Henry, T.J., and R.C. Froeschner. 1988. Catalog of the Heteroptera, or true bugs, of Canada and the continental United States. E.J. Brill, Leiden, The Netherlands. 958 pp.

Hodges, R.W. 1976. Presidential address 1976--what insects can we identify? Journal of the Lepidopterists' Society 30:245-251.

Hodges, R.W. 1994. BIOTA. Association of Systematics Collection Newsletter 21(6):72.

Hodges, R.W., et al., eds. 1983. Check list of the Lepidoptera of America north of Mexico. E.W. Classey Ltd. and the Wedge Entomological Research Foundation, London, England. 284 pp.

Holden, C. 1989. Entomologists wane as insects wax. Science 246:754-756.

Horning, D.S., Jr., and W.F. Barr. 1970. Insects of Craters of the Moon National Monument, Idaho. University of Idaho College of Agriculture Miscellaneous Series 8:1-118.

Iftner, D.C., J.A. Shuey, and J.V. Calhoun. 1992. Butterflies and skippers of Ohio. Ohio Biological Survey Bull. 9(1):1-212.

Kimble, C.P. 1965. Lepidoptera of Florida. Arthropods of Florida and Neighboring Land Areas 1:1-363.

Kosztarab, M., and C.W. Schaefer. 1990. Conclusions. Pages 241-247 in M. Kosztarab and C.W. Schaefer, eds. Systematics of the North American insects and arachnids: status and needs. Virginia Agricultural Experiment Station Information Series 90-1.

Krombein, K.V., P.D. Hurd, Jr., D.R. Smith, and B.D. Burks. 1979. Catalog of the Hymenoptera in America north of Mexico. Smithsonian Institution Press, Washington, DC. 2,735 pp.

Kumar, R., R.J. Lavigne, J.E. Lloyd, and R.E. Pfadt. 1976. Insects of the Central Plains Experimental Range Pawnee National Grassland. University of Wyoming Agricultural Experiment Station Science Monograph 32:1-74.

Leonard, M.D., ed. 1926. A list of the insects of New York with a list of the spiders and certain other allied groups. Cornell University Agricultural Experiment Station Memoir 101:1-1,121.

Linsley, E.G., and J.A. Chemsak. 1961-84. The Cerambycidae of North America. Parts 1-7. University of California Press, Berkeley.

Lutz, D. 1994. More than stamp collecting. American Scientist 82(2):120-121.

Merritt, R.W., K.W. Cummins, and V.H. Resch. 1984. Collecting, sampling, and rearing methods for aquatic insects. Pages 11-26 in R.W. Merritt and K.W. Cummins, eds. An introduction to the aquatic insects of North America. Kendall/Hunt, Dubuque, IA.

Metzler, E.H. 1980. Annotated checklist and distribution maps of the royal moths and giant silkworm moths (Lepidoptera: Saturniidae) in Ohio. Ohio Biological Survey Biological Notes 14:1-10.

Needham, J.G., and M.J. Westfall, Jr. 1955. A manual of the dragonflies of North America (Anisoptera). University of California Press, Berkeley. 615 pp.

Otte, D. 1981. North American grasshoppers. Vol. 1. Gomphocerinae and Acridinae. Harvard University Press, Cambridge, MA. 275 pp.

Otte, D. 1983. North American grasshoppers. Vol. 2. Oediodinae. Harvard University Press, Cambridge, MA. 366 pp.

Parsons, G.R., G. Cassis, A.R. Moldenke, J.D. Lattin, et al. 1991. Invertebrates of the H.J. Andrews Experimental Forest, Western Cascade Range, Oregon. V: An annotated list of insects and other arthropods. U.S. Forest Service General Tech. Rep. 290:1-168.

Procter, W. 1946. Biological survey of the Mount Desert Region. Part 7. Wistar Institute, Philadelphia, PA. 566 pp.

Rings, R.W., E. H. Metzler, F. J. Arnold, and D.H. Harris. 1992. The owlet moths of Ohio, order Lepidoptera family Noctuidae. Ohio Biological Survey Bull. 9(2):1-222.

Stanford, R.E., and P.A. Opler. 1993. Atlas of western U.S.A. butterflies, including adjacent parts of Canada and Mexico. Published by authors, Denver, CO. 275 pp.

Stannard, L.J. 1968. The thrips, or Thysanoptera, of Illinois. Illinois Biological Monographs 25:1-200.

Stone, A., C.W. Sabrosky, W.W. Wirth, et al. 1965. A catalog of the Diptera of America north of Mexico. Agriculture Handbook 276:1-1696.

Tietz, H.M. 1952. The Lepidoptera of Pennsylvania. Pennsylvania State College, School of Agriculture, Agriculture Experiment Station. State College, PA. 194 pp.

Westfall, M.J., Jr. 1984. Odonata. Pages 126-176 in R.W. Merritt and K.W. Cummins, eds. An introduction to the aquatic insects of North America. Kendall/Hunt, Dubuque, IA.

Wheeler, Q.D. 1990. Insect diversity and cladistic constraints. Annals of the Entomological Society of America 83(6):1031-1047.

Wray, D.L. 1950. Insects of North Carolina: second supplement. North Carolina Department of Agriculture, Raleigh. 59 pp.

Wray, D.L. 1967. Insects of North Carolina: third supplement. North Carolina Department of Agriculture, Raleigh. 181 pp.