Montana Field Guide

The following is taken from Rumpp (1967), Leffler (2001), and Pearson et al. (2015). Body length is 11-13 mm. Coppery-red to greenish-red above, the maculations broad, sometimes merging with each other and obscuring individual maculations, with dark base coloring reduced in extreme cases to a large wedge down the middle of the elytra and a small patch between the middle and last maculation. The anterior lateral portion of the thorax (propleuron) with brassy edges. Metallic greenish-blue below. Forehead, thorax, and legs hairy, labrum with a single tooth. Individuals from the St. Anthony Dunes, Idaho and Centennial Valley, Montana mostly with coppery-red (cupreous) elytra, those farther southwest (Minidoka area, Idaho) with mostly greenish elytra. Also known as the Idaho Dune(s) Tiger Beetle in some earlier literature (Logan 1995, and ISCE 1996).

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, Acorn 2001, and Pearson et al. 2015). Adult Cicindela arenicola, a spring-fall species, are active from early April to late July and again late August to late October or early November (Rumpp 1967, Bauer 1991, Larochelle and Larivière 2001, and Pearson et al. 2015). In Montana, adults noted from at least late May to early-September (Winton 2010, Winton et al. 2010, and Nate Kohler personal communication).

The following largely comes from Rumpp (1967), Leffler (2001), Winton (2010), and Pearson et al. (2015). Differs from the sympatric (in Montana, not Idaho) Big Sand Tiger Beetle (C. formosa) by smaller size, coppery-red to brownish-red elytra (rather than bright coppery-red), presence of greenish-blue highlights on the head and thorax lacking in C. formosa, and metallic greenish-blue below rather than metallic bluish or purplish; the maculations of both tend to be broad and sometimes coalesced. Most similar to Bruneau Dunes Tiger Beetle (C. waynei), which was once considered a greenish variant of C. arenicola with a displaced mandibular tooth, but the ranges within Idaho do not overlap, and C. waynei is not found in Montana.

Non-migratory but capable of dispersal. Wings presumably fully developed (macropterous), it is a fast runner (Larochelle and Larivière 2001). Unlikely to disperse more than 0.75 miles (1.2 km) from natal dune (Logan 1995). However, haplotype of the Centennial Valley, Montana population indicates it is closely related to the nearest population in Idaho (Goldberg et al. 2012) occupying the St. Anthony Dunes about 64 km south, with the Continental Divide between the two localities (Hendricks and Lesica 2007, Winton et al. 2010).

Adult and larval tiger beetle habitat essentially identical, the larvae live in soil burrows (Knisley and Schultz 1997). Across the range Cicindela arenicola largely restricted to sparsely vegetated sandy swales among dunes, open dune faces and tops, and blowouts that are well drained (Rumpp 1967, Bauer 1991, Logan 1995, Larochelle and Larivière 2001, and Pearson et al. 2015). Similar habitat in Montana, including sparsely vegetated sand dunes, sandy swales, blowouts, open loose sand associated with peaks of sandhills, sandy soils partially stabilized by sagebrush (Winton 2010, Winton et al. 2010, and Nate Kohler personal communication).

Larval and adult tiger beetles predaceous. In general, both feed considerably on ants (Wallis 1961, Knisley and Schultz 1997). Foods of Cicindela arenicola in the field not described but include ants, scavenged flies (bombyliids), probably various other small insects and spiders. Larvae in the field take mealworms (larval tenebrionid beetles) (Bauer 1991, Larochelle and Larivière 2001, and iNaturalist 2024).

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, and Knisley and Schultz 1997). Cicindela arenicola has a narrow range of ecological tolerance (stenotopic). Larval burrows found in well-drained ground often in flattened, bowl-shaped and grassy portions of dune swales near slopes; burrows opened in spring, plugged in summer when ambient conditions are too warm, but are reopened in autumn. Larval burrows up to 42 cm deep; food-supplemented larvae in the field developed to 3rd instar in about 13 months while larvae lacking food-supplementation developed to 3rd instar in slightly over 2 years (Rumpp 1967, Bauer 1991, and Larochelle and Larivière 2001). Adults diurnal, active on sunny, warm days at 19-45°C, hiding on windy, cloudy or rainy days. Predators not described but probably include asilid (robber) flies. Escapes by running quickly; wary and difficult to approach. Associated tiger beetle species include C. decemnotata, C. formosa, and C. tranquebarica (Rumpp 1967, Winton 2010, Winton et al. 2010, and Kohler and Martinka No date).

Life cycle of Cicindela arenicola is 2-4 years, probably depending on annual precipitation and elevation, with 2nd and 3rd instar larvae and fall adults overwintering in burrows dug in sand. Fall adults emerge in April and May and mate, oviposition begins in April and extends through June then overwintering adults die, eggs hatch in 2-3 weeks, active larval burrows peak in May but rarely open July to mid-September then open again through October, pupation in August, fresh adults (tenerals) emerge August and September before overwintering (Bauer 1991, Larochelle and Larivière 2001, Pearson et al. 2015, and iNaturalist 2024). Little information on reproductive characteristics in Montana; both sexes and all three larval instars observed in the Centennial Valley during multiple visits from mid-June to early September, and from discovery in 2008 to at least 2016, indicating a reproducing population (Winton 2010, Winton et al. 2010, and Nate Kohler personal communication).

Considered rare and of conservation concern throughout its range (ISCE 1996, Knisley et al. 2014, and Winton and Ivie No date); a Species of Concern in Montana. Sandy habitats favored by this species experience vegetation encroachment, especially from exotic and native grasses, resulting in dune stabilization as succession proceeds. This species will benefit from disturbance that retains early succession conditions. Other threats include off-road vehicle (ORV) use (seemingly not a problem for the Centennial Valley population), excessive livestock grazing, agricultural encroachment, and the potential for over-collecting (ISCE 1996, Knisley 2011, and Knisley et al. 2014). Dune stabilization is considered the greatest threat to the population in the Centennial Valley, Montana and for other sandy-habitat tiger beetle associates (Hendricks and Lesica 2007, and Winton 2010). Larval burrows could be impacted by trampling through livestock overgrazing (Bauer 1991) but grazing at appropriate stocking levels and duration could also be beneficial by keeping vegetation cover more open (simulating former bison activity). Appropriate use of limited controlled burns is another tool to maintain early succession conditions so long as a spatial mosaic of suitable microhabitats is maintained, and timing (mid to late autumn for controlled burns) does not overly impact late adult surface activity (Winton 2010, and Knisley 2011). Also, judicious use of herbicides may suppress vegetation encroachment and could be a valuable treatment tool for localized application to enhance habitat for this species (Bouffard et al. 2009).