Montana Field Guide

The following is taken from Wallis (1961), Kippenhan (1994), Knisley and Schultz (1997), Leonard and Bell (1999), Acorn (2001), and Pearson et al. (2015). Body length is 12-16 mm and body color above is dark red and purple to greenish-red or lime green with reddish edges. There are black individuals in some populations. White maculations are variable but reduced in most populations to a short isolated middle line slanting backwards. A thin rear maculation is found along the posterior tip of the elytra, sometimes with an isolated dot just anterior to the rear maculation, some individuals with a humeral dot. Some populations are entirely without maculations. Elytral margins usually lack a white connecting line, except for C. purpurea cimarrona. Below is metallic, dark green to bluish and sides of thorax are coppery. Forehead is hairy and labrum short with three teeth.

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). Adult Cicindela purpurea, a spring-fall species and one of the earliest tiger beetles to appear in spring, typically February to early June and late August to October across the range (Carter 1989, Graves and Brzoska 1991, Kippenhan 1994, Knisley and Schultz 1997, Leonard and Bell 1999, Acorn 2001, Larochelle and Larivière 2001, Pearson et al. 2015). In Montana, adults are present at least mid-March to June and late July to mid-October (Nate Kohler personal communication).

The following largely comes from Wallis (1961), Kippenhan (1994), Acorn (2001), and Pearson et al. (2015). This species is similar in the Great Plains to the Green Claybank Tiger Beetle (C. denverensis) and Common Claybank Tiger Beetle (C. limbalis) both of which have one or two white dots as the shoulder (humeral) maculation instead of none, and the middle maculation is perpendicular to the elytra margin with a definite bend or wave backward instead of a short line that angles backward. The latter species most resembles reddish forms of the Cow Path Tiger Beetle. The middle maculation of the Splendid Tiger Beetle (C. splendida) is usually a short horizontal line, and the head and thorax are green or blue in contrast to the reddish elytra. The Boreal Long-lipped Tiger Beetle (C. longilabris) east of the mountains, and the Prairie Long-lipped Tiger Beetle (C. nebraskana) could be confused with black individuals of the Cow Path Tiger Beetle but both lack a maculation on the tip of the elytra and have a bald, not hairy, forehead.

This species is non-migratory but capable of dispersal. Wings are fully developed (macropterous) it is generally a weak flier and a fast runner (Larochelle and Larivière 2001).

Adult and larval tiger beetle habitat is essentially identical. The larvae live in soil burrows (Knisley and Schultz 1997). Across the range, Cicindela purpurea is typically an upland species not associated with water. It prefers dry clay or sandy soils in grassland and prairie, openings in sparse vegetation, montane meadows to at least 9500 ft (2895 m) elevation, fields, sandy blowouts, salt and alkali flats, open paths, roadcuts, grassy roadsides, ditches, clay bottoms of washes, eroded banks, sandy beaches, and open coniferous forests. Larval burrows are often found in sloping or level clay soil (Shelford 1907, Vaurie 1950, Hooper 1969, Knisley 1984, Carter 1989, Kippenhan 1994, Knisley and Schultz 1997, Leonard and Bell 1999, Acorn 2001, Larochelle and Larivière 2001, and Kritsky and Smith 2005). In Montana, habitat includes sand hills and blowouts, sandy wallows, sandy washes, roadcuts, two-tracks, montane trails, paths through grassland slopes and along roadsides, prairie dog towns, saline areas near reservoirs, open ground near prairie rivers and streams, to at least 6706 ft (2044 m) elevation (Winton 2010, Nate Kohler personal communication).

Larval and adult tiger beetles are predaceous. In general, both feed considerably on ants (Wallis 1961, Knisley and Schultz 1997). The diet of adult Cicindela purpurea in the field includes ants, beetles (scarabeids), acridid grasshoppers. In captivity diet includes ants, beetles (scarabeids), dipterans, other soft-bodied insects, and meat. Adults able to locate ants 10-13 mm distant. Larval foods in captivity include meat (Larochelle and Larivière 2001, P. Hendricks personal observation).

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, and deeper burrows for overwintering. Adults are sensitive to heat and light and they 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). Cicindela purpurea has a broad range of ecological tolerance (eurytopic) with the exception of C. purpurea lauta. Larval burrows are generally scattered, excavated in small bare patches of clay to sandy-clay soils (sometimes stony-loamy soil). Larvae have been reported to survive flooding for up to 3 weeks (Larochelle and Larivière 2001, Pearson et al. 2015). Adults are diurnal, active early until late in the evening on hot days, solitary or in pairs, occasionally in small groups. Predators across the range include asilid (robber) flies, and various birds (crows, bluebirds, grackles, European Starling, flycatchers). They are reluctant to fly but escapes predators or disturbance by flying a few meters or running in and out of vegetation cover or hiding under grass, pieces of wood, stones, and retreats to small burrows dug at the base of clay banks, both during the night and on cool overcast days. Associated tiger beetle species include C. limbalis, C. longilabris, C. splendida, C. (= Parvindela) terricola, and C. tranquebarica (Kippenhan 1994, Larochelle and Larivière 2001, Pearson et al. 2015).

The life cycle of Cicindela purpurea is mostly 2-3 years, possibly 1 year in the warmer southeastern part of the range (Knisley and Schultz 1997, Leonard and Bell 1999, Acorn 2001, Pearson et al. 2015). Mating is from March to June, mounting may be lengthy before actual copulation. Adult females oviposit from the surface during the day to depths of 7-9 mm, often active after rains and when soil surface is moist. Oviposition occurs several days after fertilization. Eggs are cream-colored, 2 mm long and 1 mm wide, about 50 eggs are laid singly. Eggs hatch about 2 weeks after laying (Shelford 1908). Larval burrows are 8-15.0 cm in length, possibly limited in depth by compact soil where they are found (Pearson et al. 2015). The duration of larval life is about 12-13 months, third instar larvae overwinter, with pupation in July. Fresh adults (tenerals) emerge in August and September then overwinter and reach sexual maturity the following spring after hibernation. The adult lifespan is about 10 months. Interspecific copulations have been reported with C. sexguttata and C. tranquebarica (Larochelle and Larivière 2001, Brust et al. 2012). In Montana, it has been photographed copulating in late April to early June (iNaturalist [accessed 28 September 2023], Chuck Carlson personal communication).

Not considered rare or in need of special conservation management (Knisley et al. 2014). Anthropogenic disturbance that retains or creates open conditions (clay roads, paths, powerline corridors) benefits Cicindela purpurea. Exotic grasses, such as cheatgrass, could become a problem at local scales where they invade open habitats. Larval burrows could be impacted by trampling through livestock overgrazing or livestock concentrations at water sources, but grazing at appropriate times and stocking levels could also be beneficial by keeping vegetation cover more open (Knisley 2011).