Montana Field Guide

The following is taken from Wallis (1961), Carter 1989, Kippenhan (1994), Acorn (2001), and Pearson et al (2015). The body length is 11-14 mm. It is short-legged and robust, rear end rounded and elytra margins relatively parallel-sided. Above, head and thorax dark green to blue contrasting with elytra, which are intense metallic reddish-orange, sometimes with metallic green present on the anterior parts. Maculations are usually absent, or reduced to small spots and a thin, short band along outer edges of elytra. Undersides are iridescent green-blue. Labrum white in males, dark or black in females, mandible with 3 teeth. Front and top of head with white hairs, less in females (hairs restricted to base of eyes) than males.

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, and Leonard and Bell 1999). Adult Cicindela scutellaris scutellaris a spring-fall species, active period is March to October but varies somewhat: April to June and September to October in Kansas, April to July and August to September in Nebraska, mid-March to early July and late August to late September in Colorado (Carter 1989, Kippenhan 1994, Larochelle and Larivière 2001, and Pearson et al. 2015). In Montana, it is active at least from early April to early July and again September (Nate Kohler personal communication, iNaturalist 2023).

The following comes largely from Kippenhan (1994), and Pearson et al. (2015). Most similar in the west and Midwest to the Splendid Tiger Beetle (C. splendida), but that species does not occur in Montana (although reported nearby in western South Dakota). C. splendida has a green to greenish-blue head and thorax and contrasting reddish elytra, similar to C. s. scutellaris, but has a dull surface on the elytra with maculations reduced to a few lines and spots, not shiny and metallic, and usually immaculate as with C. s. scutellaris. C. splendida also tends to occur on clay soils, not sand. C. s. lecontei, with its uniformly duller reddish-maroon or olive-green dorsal surface (head to elytra) and broad ivory-colored border along the outer edge of the elytra, is unlike C. s. scutellaris in appearance. Other tiger beetles co-occurring in sandy habitats in our region, such as the Big Sand Tiger Beetle, (C. formosa), Sandy Tiger Beetle (C. limbata), and Badlands Tiger Beetle (C. decemnotata), have complete and sometimes greatly expanded maculations on the elytra.

Non-migratory but capable of dispersal. When wings are fully developed (macropterous), it is a good 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). Across the range Cicindela scutellaris scutellaris is associated with sandy soils and habitats with sparse vegetation: the more stabilized margins of sand dunes and dry grassy blowouts, sandy road cuts, sand flats, sand and gravel pits, riverine sand bars, sandy soils beneath open pine and mixed pine-oak woodlands prior to later stages of succession (Vaurie 1950, Wallis 1961, Hooper 1969, Knisley 1984, Carter 1989, Kippenhan 1994, Acorn 2001, Larochelle and Larivière 2001, Kritsky and Smith 2005, and Pearson et al. 2015). In Montana, habitat is poorly described but includes sand dunes, blowouts, and riverine sandbars, to at least 4200 ft (1280 m) elevation (Nate Kohler personal communication, iNaturalist 2023).

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 scutellaris scutellaris in the field includes grasshoppers (acridids), and in captivity ant pupae and termites. Diet of larvae in captivity includes beetle (tenebrionid) larvae and termites; larvae may occasionally cache prey in the burrow (Larochelle and Larivière 2001, Brust et al. 2012).

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, with 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 scutellaris scutellaris has a narrow range of ecological tolerance (stenotopic). Adults are diurnal and are especially active mid-day during the hottest periods, gregarious, very wary and often run through sparse vegetation. They hide in slit holes in grassy sand areas on cloudy days (Vaurie 1950, Kippenhan 1994, Larochelle and Larivière 2001, and Pearson et al. 2015). Predators of adults include birds (American Crow, Burrowing Owl), probably also spiders and robber flies (Asilidae). When disturbed makes fast looping flights (Larochelle and Larivière 2001, Spomer and Spomer 2006, and Pearson et al. 2015). Associated tiger beetle species include C. denverensis, C. formosa, C. lengi, C. limbata, C. sexgutta, C. splendida, and C. tranquebarica (Carter 1989, Kippenhan 1994, Larochelle and Larivière 2001, Kritsky and Smith 2005). Striking color pattern of C. s. scutellaris may mimic the Nuttall’s Blister Beetle, (Lytta nuttalli) (Acorn 1988, 2001, and Larochelle and Larivière 2001).

The life cycle of Cicindela scutellaris scutellaris is 2 years (Larochelle and Larivière 2001, and Pearson et al. 2015). Both third-instar larvae and adults overwinter, adults emerging in fall, then overwintering and reemerging in spring to mate. Mating is April to June. Females dig oviposition holes 35-60 mm deep during the day. Eggs are laid in dry sand. The estimated lifetime fecundity is 60-150 eggs (Brust et al. 2012). Larval burrows and larval development is probably similar to C. s. lecontei. Burrows are vertical and 25-71 cm deep, deeper in winter, closed in mid-summer. The duration of larval life is 12-13 months, with pupation in August in a chamber 25-50 mm deep branching 5-7 cm off of the main burrow. Fresh adults (tenerals) emerge in August and September (Criddle 1907, 1910; Shelford 1908, Vaurie 1950, Larochelle and Larivière 2001, Brust et al. 2012). No information on reproductive characteristics for Montana.

Not considered rare or in need of special conservation (Knisley et al. 2014). Sandy habitats favored by this species experience vegetation encroachment and stabilization as succession proceeds (Shelford 1907), and benefit from disturbance that retains a mosaic of successional conditions. Some colonies (particularly the larval burrows) could be impacted by trampling through livestock overgrazing, but grazing at appropriate times and stocking levels could also be beneficial by keeping vegetation cover more open (Knisley 2011). Prescribed fire in late autumn could also be a useful tool for sustaining habitat once larvae and adults are in overwinter burrows.