Cicindelidia sedecimpunctata

Distinguished from similar tiger beetles by the bright orange-red abdomen, which is fully exposed only during flight. The combination of orange abdominal coloration with chemical defense (benzaldehyde and cyanide) is a key identifying characteristic. When at rest, the bright abdomen is concealed, making the beetle appear more cryptic. The species is medium-sized among tiger beetles and has the typical streamlined, long-legged form of the genus.

Adults congregate around water sources including ponds, ditches, river banks, and drying waterways. Daytime aggregations occur on moist areas such as mudflats and small pools. Nocturnal roosting aggregations have been observed on dry ground away from water. Larval habitat remains poorly documented; females in captivity preferred loamy dirt from grassy hills over river sand for oviposition, suggesting larvae may develop in upland areas away from adult feeding sites.

Sonoran and Chihuahuan Deserts of the southwestern United States (Arizona, New Mexico), extending south through Mexico to Costa Rica. U.S. and northern Mexican populations represent the nominate subspecies; southern populations are classified into four additional subspecies.

Adults emerge in early to mid-June, before summer monsoonal rains, and remain active through summer. By late July and August, adults disperse to higher elevations. In the Gila River area of southwestern New Mexico, adults have been observed from June through late summer.

Adults are predatory, feeding on stranded tadpoles and other aquatic organisms at water's edge. At night aggregations, occasional individuals have been observed feeding on moths attracted to lights. Larvae are predatory, feeding on small arthropods such as ants that pass their burrow entrances.

Females deposit eggs in soil; captive females preferred loamy dirt from grassy hills over pure sand. Eggs hatch into first instar larvae that construct vertical burrows with circular entrances, enlarging them (1–3 mm diameter) through three instars. Larvae overwinter at the bottom of burrows at least 15 cm deep, becoming quiescent. Pupation and adult emergence timing poorly documented in the wild. First and second instars have been described from captive rearing.

Primarily diurnal but attracted to lights at night. Famous for forming large daytime aggregations of up to several thousand individuals along drying waterways. A nocturnal communal roosting behavior has been documented, with 200–300 beetles per square meter observed resting on dry ground at night, showing relative inactivity compared to daytime aggregations. Adults are fast runners and strong fliers. When captured, adults release benzaldehyde and cyanide as chemical defense.

Predator in riparian and aquatic-edge ecosystems, with aggregations potentially exerting significant predation pressure on stranded tadpoles and other small aquatic organisms. The species serves as prey for robber flies (Asilidae), against which its aposematic coloration and chemical defense provide protection.

Subject of citizen science research on larval biology and oviposition habitat. Collected for scientific study and terrarium rearing. Chemical defense (benzaldehyde) produces characteristic 'fruity' smell familiar to collectors.

• Cicindela maruthaBoth species are found in arid southwestern habitats and exhibit similar behavior of moving away from water to oviposit; C. marutha travels up to half a mile to sand dunes, while C. sedecimpunctata may use nearby grassy hills.

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
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