Montana Field Guide

The following is taken from Knisley and Schultz (1997), Leonard and Bell (1999), and Pearson et al. (2015). The length is 16-18 mm and it is the largest tiger beetle in Montana. Reddish-bronze to dark brown above with broad but distinct maculations connected to each other along the lateral margins of elytra. Metallic green with coppery reflections or brownish below. Lateral portions of head, thorax, and abdominal sternites with numerous white setae. Broad zone of intergradation with C. formosa formosa, which is bright coppery red above, metallic purple below (see Formosa subspecies account). The former “manitoba” subspecies (Wallis 1961) is currently treated as a variant of C. f. generosa (Pearson et al. 2015).

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 formosa generosa in the southern part of its range are active from March to July and again August to October. At higher latitudes some adults may be present throughout summer (Larochelle and Larivière 2001, Pearson et al. 2015). In Montana, some adults are active from mid-April to at least mid-September (Criddle 1925, Nate Kohler personal communication).

The following largely comes from Pearson et al. (2015). This species differs from C. formosa formosa in coloration, which is bright coppery red above instead of reddish-bronze to dark brown, and metallic purple below instead of metallic green with coppery reflections. Differs from C. f. gibsoni in coloration (which is dark red to purple above and metallic bluish-violet below), and maculations (maculations expanded, sometimes to cover much of elytra except for a dark wedge down the midline). Differs from the similarly colored and sometimes sympatric Blowout Tiger Beetle (C. lengi) by its bulkier larger size, shorter and wider labrum; also the front (shoulder) maculation is relatively shorter, and the maculations generally thicker overall. The humeral lunule (maculation) is not hooked, as is found with the Hairy-necked Tiger Beetle (C. hirticollis).

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

Adult and larval tiger beetle habitat essentially identical, the larvae live in soil burrows (Knisley and Schultz 1997). Across the range Cicindela formosa generosa prefers dry upland sandy areas with little vegetation and no standing water (sand dunes, sand hills), often in short grass and forbs near dune margins, ditches, road cuts, sandy fields, sand flats, sandy beaches along water courses (Wallis 1961, Larochelle and Larivière 2001, Pearson et al. 2015). In Montana, probably found in stabilized sandy dunes, sandy road cuts and paths, and sandy beaches along water courses.

Larval and adult tiger beetles are predaceous. In general, both feed considerably on ants (Wallis 1961, Knisley and Schultz 1997). Larval Cicindela formosa generosa feed on ants, adults on ants, carabid beetles, chrysomelid beetles, scarabid beetles (Willis 2000, Larochelle and Larivière 2001), and probably other small insects and spiders.

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 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 formosa generosa has a narrow range of ecological tolerance (stenotopic). Larval burrows are up to 33 cm deep in sand with a pit near the entrance (unique) used for trapping insects, burrows closed in summer. Adults are diurnal, gregarious in delimited sandy habitats (often occurring in large numbers), become active at 18°C, and burrow in sand to escape high temperatures from direct sunshine. Predators include asilid (robber) flies. Escapes by flying quickly, sometimes to 100 m if pursued, while making an audible buzz in flight, then seeking cover in vegetation once landing. Adults may live 10-12 months. Wary and difficult to approach. Other associated tiger beetle species include Blowout Tiger Beetle (C. lengi) and Festive Tiger Beetle (C. scutellaris) (Leonard and Bell 1999, Larochelle and Larivière 2001).

The life cycle of Cicindela formosa generosa is 2-3 years, depending on elevation and latitude (Larochelle and Larivière 2001, Pearson et al. 2015). The following is taken from Leonard and Bell (1999) and Larochelle and Larivière (2001). Mating is reported May to July. The female oviposits in slightly shifting sand and some larvae reach the third instar by September others take 24 months. Burrows close by October and overwinter as larvae about 30-200 cm below soil surface. Larvae open burrows in spring then pupate in side tunnel about 10 cm below soil surface and about 12 months after hatching. Other larvae may take 24 months to pupate. Some adults overwinter in pupal chamber 10-120 cm below soil surface before emerging in spring, others emerge in autumn, then burrow and overwinter before reemerging in spring.

Not considered rare or in need of special conservation management (Knisley et al. 2014), but see account for C. f. gibsoni. Sandy habitats favored by this subspecies experience vegetation encroachment and stabilization as succession proceeds, and benefit from disturbance that retains early succession 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, as could appropriate use of controlled burns (Knisley 2011).