|For: Western Forest Insects
By: Kamal J.K. Gandhi
Draft: 8 February, 2008
FAMILY CARABIDAE—GROUND BEETLES
Ground beetles (Coleoptera: Carabidae) comprise a large family of generally brown to black and occasionally metallic and bi- or tri-colored beetles (Lindroth 1961-69, Ball and Bousquet 2000). Adults vary in size from 0.7 to 66 mm (Ball and Bousquet 2000). Although the morphological characters of ground beetles vary tremendously as an adaptation to various environments, the uniting characters of this family includes the first abdominal sternum subdivided by the hind-coxae, large hind trochanters, metasternum with transverse sutures just in front of the hind coxae, tarsi 5-5-5, and generally filiform antennae (Borror et al. 1992).
The ground beetles, Carabidae (Arnett 1960, Hatch 1953), are a large family of small to large, generally black and shiny, occasionally metallic, strong-jawed, ground-inhabiting, mostly nocturnal beetles. In daytime the adults hide under stones and logs, in litter, and in other out-of-way places. When disturbed, many give off a strong odor. Most feed upon insects, especially caterpillars, hence are largely beneficial. Some feed on plant materials, including tree seeds. The larvae move about freely. They are flattened, hairless, tough skinned, and tapered at both ends.
Ground beetles inhabit a variety of habitats, and species are either hygrophilic, mesophilic, xerophilic, cavernicolous or arboreal. During the day, adult ground beetles can be found under stones, logs, snags, vegetation, and litter debris. When disturbed, many species such as those in the genus Brachinus and Chlaenius, may either spray or ooze defensive compounds. Adults are generally nocturnal and feed in the night. Most ground beetles are generalist or specialist predators on adult and larval arthropods (Figure 1); some are scavengers on other arthropods and phytophagous on plant seeds; and few are myrmecophiles or parasitoids as larvae. Thus, ground beetles are an important component of the food-chain in the litter layer, and aid in nutrient cycling within forested ecosystems.
Ground beetles are species-rich and abundant in western forests. The highest species richness is documented in California (671), followed by British Columbia (485), Oregon (471), Washington (442), Colorado (406), Alberta (399), Montana (353), Idaho (322), Wyoming (288), Alaska (244), and Nevada (191) (Bousquet and Larochelle 1993). The highest species for exotic ground beetles is documented in British Columbia (27 species), followed by Washington (23), Oregon (17), California (10), Alberta (9), Idaho (7), Montana (5), Colorado (2), Wyoming (2), Alaska (1), Nevada (1), and Utah (1) (Gandhi, unpublished data). Most of the exotic ground beetles are synanthropogenic, but there are some species, such as Pterostichus melanarius (Illiger) (Figure 2) and Carabus nemoralis (Müller), that are sometimes common in forests. Although there is little information about how exotic ground beetles may affect native species, their introduction and spread should be minimized as much as possible.
Some of genera most likely to be encountered in and adjacent to the forests include Calosoma, Pterostichus, and Scaphinotus. Calosoma species are among the largest ground beetles (13-36 mm). They feed on lepidopterous larvae associated with trees and shrubs, and other insects. Many species of Calosoma are native in the West, but none of them are reported to be effective in control of forest pests. Calosoma frigidum Kirby is recorded as a predator of the forest tent caterpillar (Malacosoma disstria Hübner) in Minnesota (Hodson 1941), and it does the same in the western forests (D.W. Langor, personal communication). The European species, C. sycophanta (Linnaeus), is an important arboreal predator of the larvae and pupae of gypsy moth in the northeastern forests of the USA (Weseloh 1985). Efforts have been made without success to introduce this species to British Columbia, Washington, California, New Mexico, and Colorado against various defoliators, including the Douglas-fir tussock moth [Orgyia pseudotsugata (McDunnough)], western hemlock looper [Lambdina fiscellaria lugubrosa (Hulst)], California oakworm (Phryganidia californica Packard), satin moth [Leucoma salicis (Linnaeus)], and western tent caterpillar [Malacosoma californicum (Packard)].
Pterostichus is a species-rich genus in the western forests especially in California, and are generally medium-sized, rather flattened, black beetles. They are predaceous, but some are among the species of ground beetles that also feed on plant material. Studies in Washington indicated that P. algidus LeConte, P. amethystinus Mannerheim, P. herculaneus Mannerheim, P. melanarius, and P. pumilus pumilus Casey feed on Douglas-fir seeds (Dick and Johnson 1958, Johnson et al. 1966). Pterostichus algidus was found to be among the prime seed-eaters, and its peak activity time coincided with the period of seed fall in October (Johnson et al. 1966). Adults of P. lama (Ménétriés) were observed to feed on workers of Zootermopsis nevadensis (Hagen) in logs and stumps of Ponderosa pine (Linsley and Michener 1943).
Scaphinotus species are large, long-legged, generally black, sometimes metallic, with a strong constriction between the thorax and elytra and notably elongate head and mandibles. They are fast-moving beetles, some of which live in forests where they feed upon snails, slugs, and caterpillars. Scaphinotus angusticollis (Mannerheim) occurs in coastal forests from northern California to Alaska. It has been reported to prey upon the larvae and pupae of the western hemlock looper.
As ground beetles are species-rich and numerically abundant in the litter layer in the western forests, they are considered crucial to forest biodiversity and health in managed forests. Ground beetle species are also highly sensitive to changes in their micro-habitat conditions. Hence, during the past few decades, they have been widely used as an indicator taxon for assessing the effects of habitat changes due to natural disturbances such as wildfires, and anthropogenic disturbances such as clearcutting, prescribed burning, and salvaging on forest insect biodiversity (e.g., Spence et al. 1996, Gandhi et al. 2001, 2004, Apigian et al. 2006, Phillips et al. 2006).
Calosoma (Burgess and Collins 1917, Gidaspow 1959) is a large genus of large, generally black beetles that feed upon caterpillars and other insects. Many species of Calosoma are native in the West but none of them is reported effective in control of forest pests. Calosoma f rigidum Kirby is recorded as a predator of the forest tent caterpillar. Efforts have been made without success to colonize C. sycophants (L.) in British Columbia, Washington, California, New Mexico, and Colorado against various insects, including the Douglas fir tussock moth, western hemlock looper, California oakworm, satin moth, and western tent caterpillar. This European ground beetle is an important predator of the gypsy moth. The adults and larvae both climb trees in search for prey. The adults have black bodies and brilliant green elytra.
Pterostichus (Arnett 1960) is a large genus of medium-sized, rather flattened, black beetles. They are predaceous, but some are among the species of ground beetles that also feed on plant materials.
Soil-inhabiting insects, principally ground beetles, cause significant loss of Douglas-fir seeds. Studies in Washington and California implicated Pterostichus algidus LeConte (Johnson et al. 1966) (fig. 141) as the principal ground beetle that feeds upon Douglas-fir seeds.
Scaphinotus (Arnett 1960) contains numerous species in the West. They are large, long-legged, generally black, sometimes metallic beetles, strongly constricted between the thorax and
elytra. They are fast-moving beetles, some of which live in forests where they feed upon snails, slugs, and caterpillars.
Scaphinotus angusticollis (Mannerheim) (fig. 142) occurs in coastal forests from northern California to Alaska. It has been
FIGURE 142.—Adult of Scaphinotus angusticollis, 22 mm long, predaceous in coastal forests.
FIGURE 141.—Adult ground beetle, Pterostichus algidus, carrying off a Douglas-fir seed.
Apigian, K.O., Dahlsten, D.L., and Stephens, S.L. 2006. Fire and fire surrogate treatment effects on leaf litter arthropods in a western Sierra Nevada mixed-conifer forest. Forest Ecology and Management 221: 110-122.
Ball, G.E., and Bousquet, Y. 2000. Carabidae Latreille, 1810. Pages 32-132 in R.H. Arnett Jr., and M.C. Thomas, editors. American Beetles: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia, Volume I. CRC Press, Boca Raton, Florida.
Borror, D.J., Triplehorn, C.A., and Johnson, N.F. 1992. An introduction to the study of insects. Sixth Edition. Harcourt Brace College Publishers.
Bousquet, Y., and Larochelle, A., 1993. Catalogue of the Geadephaga (Coleoptera: Trachypachidae, Rhysodidae, Carabidae including Cicindelini) of America North of Mexico. Memoirs of the Entomological Society of Canada No. 167, Ottawa, Ontario.
Dick, J., and Johnson, N.E. 1958. Carabid beetles damage Douglas-fir seeds. Journal of Economic Entomology 51: 542-544.
Gandhi, K.J.K., Spence, J.R., Langor, D.W., and Morgantini, L.E. 2001. Fire residuals as habitat reserves for epigaeic beetles (Coleoptera: Carabidae and Staphylinidae). Biological Conservation 102: 131-141.
Gandhi, K.J.K., Spence, J.R., Langor, D.W., Morgantini, L.E., and Cryer K.J. 2004. Harvest retention patches are insufficient as stand analogues of fire residuals for litter-dwelling beetles in northern coniferous forests. Canadian Journal of Forest Research 34:1319-1331.
Hodson, A.C. 1941. An ecological study of the forest tent caterpillar, Malacosoma disstria Hbn., in northern Minnesota. University of Minnesota Agricultural Experiment Station, Technical Bulletin 148, St. Paul, Minnesota.
Johnson, N.E., Lawrence, W.H., and Ellis, I.D. 1966. Seasonal occurrence of ground beetles (Coleoptera: Carabidae) in three habitats in southwestern Washington. Annals of the Entomological Society of America 59: 1055-1059.
Lindroth, C.H. 1961-69. The ground beetles (Carabidae, excl. Cicindelinae) of Canada and Alaska. Parts 1-6. Opuscula Entomologica Supplementa: I, 20, 24, 29, 33, 34.
Linsley, E.G., and Michener, C.D. 1943. Observations of some Coleoptera from the vicinity of Mt. Lassen, California. Pan-Pacific Entomologist XIX: 75-79.
Phillips, I.D., Cobb, T.P., Spence, J.R., and Brigham, R.M. 2006. Salvage logging, edge effects, and carabid beetles: connections to conservation and sustainable forest management. Environmental Entomology 35: 950-957.
Spence, J.R., Langor, D.W., Niemelä, J., Cárcamo, H.A., and Currie, C.R. 1996. Northern forestry and ground beetles: the case for concern about old-growth species. Annales Zoologici Fennici 33: 173-184.
Weseloh, R.M. 1985. Predation by Calosoma sycophanta L. (Coleoptera: Carabidae): Evidence for a large impact on gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), pupae. Canadian Entomologist 117: 1117-1126.
Figure 1. Promecognathus species attacking a millipede. Members of this genus are known to be specialized predators of millipedes in the western forests. Photo Credit: Kipling W. Will, University of California, Berkeley, California.
Figure 2. Pterostichus melanarius (Illiger), a European carabid beetle that is well-established in North American urban and forested landscapes. Photo Credit: Henri Goulet and Yves Bousquet, Agriculture and Agri-Food Canada, Ottawa, Ontario.
The text for the carabid beetle section has been peer-reviewed by the two following researchers:
Dr. David W. Langor
Entomologist, Biodiversity and Pest Management
Northern Forestry Centre
Canadian Forest Service, Natural Resources Canada
5320 - 122 Street
Edmonton, Alberta, Canada
Dr. Kipling W. Will
Associate Professor/Insect Systematist
Associate Director,Essig Museum of Entomology
137 Mulford Hall
ESPM Dept.- Organisms & Environment Div.
University of California
Berkeley, California 94720
reported to prey upon the larvae and pupae of the western hemlock looper. Adults are 20 to 24 mm long.