Acmaeodera riograndei

Acmaeodera riograndei can be distinguished from similar small Acmaeodera species by its distinctive coloration and pattern. Based on field observations, it resembles very small A. starrae or A. robigo in general form. The species was initially recognized by comparison with Nelson's original description illustration. Definitive identification requires examination of specimens, as field identification is challenging due to similarity with other small, pale-marked Acmaeodera species. It is smaller than A. quadravittatoides and A. neoneglecta, with which it co-occurs on cactus flowers.

Dry, rocky canyonlands with sparse vegetation. Documented from juniper chaparral and canyon slopes in the Devils River area of Val Verde County, Texas. The species occurs in areas with exposed, steep-sloped canyon walls where Echinocereus enneacanthus carnosus (strawberry cactus) grows. Plants are typically sparsely distributed on canyon slopes or canyon rims where footing is precarious.

Originally described from the Big Bend region of Texas. In 2022, documented from Gold Mine Canyon and Devils River area in Val Verde County, Texas, extending the known range approximately 250 miles east-southeast of the type locality. GBIF records indicate presence in Central America and North America, though specific Central American localities are not detailed in available sources.

Adults active in late May to early June. Documented flying to cactus flowers during hot daytime conditions, with peak activity observed when temperatures approached 100–105°F. Flowers of Echinocereus enneacanthus carnosus appear to be the primary adult activity site during this period.

• Echinocereus enneacanthus carnosus - Adult feeding siteAdults observed feeding on flowers; larvae likely develop in roots or stems of this host or associated woody plants

Adults are strong fliers that actively seek out blooming cactus flowers. They have been observed flying in to flowers during midday heat, with multiple individuals accumulating on individual flowers. When flowers close in late afternoon or early evening, adult activity ceases. Adults appear to be wary and quick to take flight when disturbed.

• Acmaeodera starrae (now regarded as A. robigo)Very similar small size and general appearance; distinguished by subtle differences in coloration and maculation pattern
• Acmaeodera neoneglectaCo-occurs on same cactus flowers but larger and with different elytral pattern
• Acmaeodera quadravittatoidesCo-occurs on same flowers but larger with distinct quadrate vittae

• Buprestidae
• Acmaeodera
• rare species
• cactus-associated
• Texas endemic
• metallic wood-boring beetle

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• 2022 Six-State Insect Collecting Trip iReport | Beetles In The Bush