Montana Field Guide

The following is taken from Wallis (1961), Acorn (2001), and Pearson et al. (2015). Body length is 11-13 mm. Uniformly dark brown above but some individuals are greenish. Maculations are complete, thin, often reduced to dots instead of crescents or lines, marginal line is absent on the middle of the elytra, middle band with abrupt bend to rear forming an “elbow.” Below, metallic blue or purple. Forehead with only a few hairs (setae) above eyes, a small cluster near the inner front edge of the eyes; first antennomere with 3 sensory setae and 5 or fewer accessory setae, labrum short with 1 tooth.

Tiger beetle life cycles fit two general categories based on adult activity periods. “Spring-fall” beetles emerge as adults in late summer and fall, then overwinter in burrows before emerging again in spring when mature and ready to mate and lay eggs. The life cycle may take 1-4 years. “Summer” beetles emerge as adults in early summer, then mate and lay eggs before dying. The life cycle may take 1-2 years, possibly longer depending on latitude and elevation (Kippenhan 1994, Knisley and Schultz 1997, Leonard and Bell 1999, and Pearson et al. 2015). Adult Cicindela oregona oregona a spring-fall subspecies, found March to November but mostly June-July and September-October (Larochelle and Larivière 2001); late March to mid-September in Nevada (Sumlin 1976), early June to late September in northern California (Smith and Bronson 2003), May to August in south-central Washington (Looney et al. 2014). In Montana, reported early April to mid-October, which probably includes intergrades with C. oregona guttifera (Nate Kohler personal communication, iNaturalist 2024).

The following comes largely from Wallis (1961), Kippenhan (1994), Acorn (2001) and Pearson et al. (2015). Most similar in appearance to the Twelve-spotted Tiger Beetle (Cicindela duodecimguttata) but C. oregona oregona and this species rarely if ever overlap; Cicindela duodecimguttata usually has a distinct or remnant short white marginal line along middle of the outer edge of the elytra, lacking in subspecies of C. oregona, and the forehead of C. oregona, is mostly hairless, not hairy as with Cicindela duodecimguttata. The Dispirited Tiger Beetle (C. depressula) has a middle band (maculation) with a shallow, wave-like bend to the rear with no sharp turn, whereas C. oregona has a sharp bend rearward, forming a distinct “elbow.” The Bronze Tiger Beetle (C. repanda) has a distinct, if incomplete, marginal band on the outer edge of the elytra that is lacking in C. oregona, and the forehead is hairy, not mostly hairless. C. oregona guttifera, the other subspecies present in Montana, has an upper surface usually rich brown, the maculations are complete and relatively thicker, the undersurface is metallic coppery. Intergrades between the C. oregona and C. oregona guttifera, have intermediate characteristics, sometimes with thin maculations but coppery on the underside of the thorax (see Acorn 2001).

Non-migratory but capable of dispersal. When wings are fully developed (macropterous), it is generally a weak flier and fast runner (Larochelle and Larivière 2001).

Adult and larval tiger beetle habitat are essentially identical, the larvae live in soil burrows (Knisley and Schultz 1997). Cicindela oregona oregona is found close to water on sparsely vegetated soils of various fluvial habitats, mudflats, alkali lake shores, salt marshes, livestock reservoirs, edges of ponds, freshwater lakes, drainage channels at hot springs and fumeroles, sand and gravel banks of rivers, streams and creeks, sand bars, dunes, other river sand deposits, coastal trails, beaches, and tidal flats (Vaurie 1950, Wallis 1961, Acorn 2001, Larochelle and Larivière 2001, Smith and Bronson 2003, Rogers and Rogers 2004, Cornelisse and Hafernik 2009, Looney et al. 2014, Pearson et al. 2015, and Sauder 2017). In Montana, habitat is similar to elsewhere inland, including dunes and two-tracks near rivers, sand bars and riverbanks, along streams, shores of freshwater lakes and reservoirs, reclamation pond edges, and fishing access sites (Nate Kohler personal communication; iNaturalist 2024).

Larval and adult tiger beetles are predaceous. In general, both feed considerably on ants (Wallis 1961, and Knisley and Schultz 1997). Adult foods of Cicindela oregona oregona in the field include various small arthropods, adult damselflies and midge (chironomid) larvae (30-31% success rate on the latter), also scavenge dead and dying beetles (dytiscids), dipterans, lepidopterans and odonates around fumaroles and near hot springs; foods in captivity include small crickets and house flies. Larval foods in the field include ants, damselflies, tabanid flies, and beetles (coccinelids); larvae can be cannibalistic when coming into contact (Larochelle and Larivière 2001, Kippenhan 2002, Rogers and Rogers 2004, Lyons 2015).

Larval tiger beetles live in burrows and molt through three instars to pupation, which also occurs in the larval burrow. Adults make shallow burrows in soil for overnight protection, deeper burrows for overwintering. Adults are sensitive to heat and light and are most active during sunny conditions. Excessive heat during midday on sunny days drives adults to seek shelter among vegetation or in burrows (Wallis 1961, Knisley and Schultz 1997, and Pearson et al. 2015). Cicindela oregona oregona has wide ranges (eurytopic) of ecological tolerance. Adults are diurnal and gregarious, becoming active at about 15°C, escapes by slow flights of up to 3 m or burrows into shallow sand when pursued, quite wary, releases defensive secretions when captured (Larochelle and Larivière 2001). Predators of adults include frogs and gnaphosid spiders, probably birds and robber flies (asilids); larvae parasitized by bee flies (bombyliids) and probably tiphiid wasps. Associated tiger beetle species include C. columbica, C. duodecimguttata, C. (=Cicindelidia) hemorrhagica, C. hirtcollis, C. repanda, and C. tranquebarica (Larochelle and Larivière 2001, Smith and Bronson 2003, Pearson et al. 2015, and Sauder 2017).

Life cycle of Cicindela oregona is 2 years. Mate in May and July; females oviposit in May and July. Larval burrows are usually clustered, 12-30 cm deep and 1.5-3.0 mm in diameter (depending on instar), and vertical if on flats, horizontal if in banks, excavated in open and moist loose sand near water. Overwinter as third-instar larvae, reemerge in spring then pupate in early summer, sexually immature adults (fresh tenerals) emerge in August and September then overwinter before reemerging the following spring to mate. Interspecific copulation observed with C. duodecimgutata, C. repanda, and C. willistoni (Vaurie 1950, Acorn 2001, Larochelle and Larivière 2001, Cornelisse and Hafernik 2009, Lyons 2015, and Pearson et al. 2015). Mating observed in Montana in late May and late July (iNaturalist 2024), otherwise no information).

Not considered rare or in need of special conservation management (Knisley et al. 2014). Cicindela oregona oregona may be sensitive to altered river and stream flows through damming and channelization, which alters sediment deposition, especially sand. Retention and restoration of natural stream and river sediment-deposition processes will also benefit this subspecies. Early-succession habitats near water favored by this subspecies experience vegetation encroachment as succession proceeds for whatever reason (Shelford 1907, Knisley 1979), and benefit from disturbance that retains a mosaic of successional conditions. Some colonies (particularly larval burrows) could be impacted by trampling from human foot traffic and livestock overgrazing or access to water sources at lakes, streams and rivers (Cornelisse and Hafernik 2009, Knisley 2011). Grazing at appropriate times and stocking levels, however, could be beneficial by keeping vegetation cover more open.