Montana Field Guide

The following is taken from Pearson et al. (2015): length is 13-16 mm; shiny green, blue-green or black on the upper surface, usually without maculation. If maculation is present, they are obscure or reduced to a very thin white dash on the posterior tip of each elytron. Undersurface and legs are the same color as the back. Females have a long black upper lip (labrum), which is shorter and ivory-white in males.

Tiger beetle life cycles fit into two general categories. “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 (Knisley and Schultz 1997, Leonard and Bell 1999). Cicindela plutonic appears to have a spring-fall life cycle at lower elevation, and a summer life cycle at higher elevation. Adults at lower elevations in Oregon, Idaho and Utah reported February to April, June to July, and again September to October. Adults at higher elevations (2438-3000 m) in California, Nevada and Oregon have been reported active in early June to early July with a fall activity period unreported (Crazier 1936, Larochelle and Larivière 2001, Pearson et al. 2015).

The following comes largely from Pearson et al. (2015). This species is most similar to the black variant of the Cow Path Tiger Beetle (Cicindela purpurea audubonii) but differs by lacking the thin angled middle line on the elytra and is found only west of the Rocky Mountains. Black variants of the Long-lipped Tiger Beetle (Cicindela longilabris) differ by having a labrum longer than wide, a general lack of setae on the forehead, and usually more maculation on the elytra.

The Alpine Tiger Beetle is non-migratory but is capable of dispersal. When wings are fully developed (macropterous) it is a strong flier and 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). Habitat for Cicindela plutonica includes sparsely vegetated rocky hillsides to 3000 m elevation in California, Nevada and Oregon, sometimes near melting snow. At lower elevations in bare patches of soil among sagebrush and high desert vegetation, and in adjoining roads and washes. It can also be found in alkaline and semi-alkaline areas, sand dunes, scab-rock flats, and foothill brush and pastures. Open ground can be dry, sandy or rocky, alkaline, and sparsely vegetated with grass or forbs (Crazier 1936, Larochelle and Larivière 2001, Pearson et al. 2015).

Larval and adult tiger beetles are carnivorous. In general, both feed considerably on ants (Wallis 1961, Knisley and Schultz 1997). The diet of Cicindela plutonica is unreported but probably consists of small insects and spiders.

Larval tiger beetles live in burrows and molt through three instars. 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). Cicindela plutonica has a wide range of ecological tolerance (eurytopic) as evidenced by the variety of habitats in which it occurs. Adults are diurnal; inactive on overcast days and almost inactive on windy days. Predators on adults are not reported, but robber flies are likely. The species escapes by flying quickly for some distance.

Other associated tiger beetle species include Long-lipped Tiger Beetle (Cicindela longilabris), Cow Path Tiger Beetle (Cicindela purpurea), Western Tiger Beetle (Cicindela oregona) and Oblique-lined Tiger Beetle (Cicindela tranquebarica) (Crazier 1936, Larochelle and Larivière 2001). Apparently occurs in small colonies of less than a hectare in size, with considerable distance between colonies (Pearson et al. 2015).

Mating reported in June (Larochelle and Larivière 2001). Larvae and larval biology is unknown (Pearson et al. 2015).

Not considered rare or in need of special conservation management (Knisley et al. 2014), but scattered colonies may make them vulnerable to disturbance or extirpation. Management needs are hindered by a general lack of information or survey effort for this species.