Amblycheila cylindriformis

Adults are distinguished from all other North American tiger beetles by their combination of enormous size (25–38 mm), cylindrical body shape, somber black coloration, small eyes, and strictly nocturnal activity. Flightlessness separates them from most other tiger beetles. Larvae are identified by their exceptional size (up to 62 mm), two pairs of eyes with the anterior pair larger, and the diagnostic hook arrangement on the 5th abdominal segment: simple thorn-like hooks with middle and inner hooks distinctly separated at the base, surrounded by stout setae. Burrows are large (6–8 mm diameter), almost perfectly round with clean beveled edges, slightly D-shaped to match the larval head profile, and often clustered in proximity.

Native mixed-grass prairie and grassland areas of the Great Plains. Adults are found walking on bare ground, particularly on red clay/gypsum exposures on lower talus slopes. Larvae construct burrows in specific soil types including Colby silt loam, with preference for areas with particular slope profiles. Suitable microhabitats include barren soil patches amongst vegetation, clay banks near streams, ravines, and vertical clay bluff faces.

Great Plains of central North America. Documented from Texas north to far-southwestern South Dakota (the northernmost limit), including Oklahoma, Kansas, and Nebraska.

Adults are active during summer months, with peak activity in June and July. The species is strictly nocturnal, with adults emerging after dark (observed activity beginning around 9 pm).

Development includes egg, larval (three instars), pupal, and adult stages. Larval development is prolonged; one individual collected as a 2nd instar larva took over 3 years to reach adulthood, with the pupal stage occurring in a plugged burrow. Larval burrows extend to depths of a meter or more. Adults construct burrows in clay soil with ragged openings, unlike the perfectly-shaped larval burrows, and spend much time in these burrows.

Strictly nocturnal; adults walk with a lumbering, deliberate gait distinct from the rapid, jerky movement of most tiger beetles, lifting each foot relatively high. Adults are not fast runners and do not pause frequently, making them difficult to photograph in the field. Larvae are sit-and-wait predators that anchor themselves in burrows using abdominal hooks. Adults can be collected in pitfall traps.

Larvae function as subterranean predators in grassland soil ecosystems. Their deep burrowing activity likely contributes to soil aeration and nutrient cycling in prairie habitats.

Collected by entomologists for study and curation; the species represents a notable target for specialist collectors due to its size and restricted distribution. Adults are reportedly easy to handle but possess large mandibles capable of delivering a painful bite.

• Amblycheila hoversoniAlso a giant flightless tiger beetle of the same genus; slightly larger, making it the largest tiger beetle in the Western Hemisphere. Restricted to South Texas, separating it geographically from A. cylindriformis.
• Tetracha speciesLarvae share two pairs of hooks on the 5th abdominal segment, but Tetracha hooks touch at the base rather than being distinctly separated, and lack the cluster of stout setae around the hook base present in Amblycheila.
• Cicindela (sensu lato) speciesMost tiger beetles are diurnal, fast-running, and capable of flight; adults of A. cylindriformis are immediately distinguished by nocturnal habits, flightlessness, enormous size, and lumbering gait.

• tiger beetle
• flightless
• nocturnal
• Great Plains
• grassland
• burrowing
• giant
• Cicindelidae
• Carabidae
• soil-dwelling larvae
• endemic to North America
• summer-active
• clay soil habitat
• talus slopes
• pitfall trap susceptible
• prolonged larval development
• adult burrow construction

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• How to collect larvae of Amblycheila cylindriformis | Beetles In The Bush
• Hunting the Great Plains giant tiger beetle | Beetles In The Bush
• The Power of Impulse | Beetles In The Bush
• Microhabitat Preference of Great Plains Giant Tiger Beetle Larvae,Amblycheila cylindriformisSay (Coleoptera: Carabidae: Cicindelinae), is Influenced by Soil Slope Profile