Family Ripiphoridae - Wedge-shaped Beetles

Ripiphoridae Gemminger and Harold, 1870. Sometimes spelled Rhipiphoridae, but that appears not to be taxonomically correct!

Family first described by Gemminger (Max Gemminger 1820-1867, see Wikispecies) and Harold (Scarab Workers, Wikispecies), 1870.

Named after the genus Ripiphorus--see that guide page for origin of name.

Arnett, p. 463, lists six genera and 44 species. (1)

nearctica.com lists six genera and 47 species for North America.

Subfamily Ripiphorinae contains tribes Macrosiagonini (includes genus Macrosiagon) and Ripiphorini (includes genus Ripiphorus). Subfamily Ripidiinae contains genus Ripidius, see Beetles of Florida.

3-15 mm

Small to medium-sized beetles, sometimes found on flowers. Similar to Tumbling Flower Beetles, but have fan-like (flabellate) antennae, esp. in males. Abdomen blunt. Tarsal formula 5-5-4 (rear legs with 4 tarsomeres, others with 5).

In eastern North America, there appear to be three widespread genera of wedge-shaped beetles. Macrosiagon has long elytra, covering abdomen, and a point of the thorax covering the scutellum. Species are usually orange/yellow and black. Some species are medium-sized, circa 9 mm. Ripiphorus has very short elytra, and most(?) species are smaller, circa 4-6 mm. Pelecotoma flavipes has full-length elytra, is small, 4-5 mm. It is piceous-black with yellowish antennae and legs. (2)

North America. Macrosiagon (10 species) and Ripiphorus (30 species) are widespread in eastern North America. Pelecotoma flavipes is found in southeast. Other genera are found in southwest.

Fields, etc. with flowers.

Summer.

Adults found on flowers, so perhaps take pollen and/or nectar, though they also leave eggs on flowers.

Life cycle is hypermetamorphic. Parasites on bees or wasps, or, (in tropics?) cockroaches. Specifically, members of subfamily Ripiphorinae parasitize wasps (tribe Macrosiagonini, wasps, tribe Ripiphorini, bees). Subfamily Ripidiinae parasitizes cockroaches. Eggs are laid on or near flowers, sometimes inside unopened flower buds. Larvae attach to visiting bees and are taken back to nest, where they are internal parasites of larval hymenoptera, in some cases only in early stages. (In tropics, some species are parasites of cockroaches.) Some are reported to feed on leaves in later stages. Adults have short lifespan, aren't seen too frequently.

The image below likely depicts ripiphorid triangulins (young larvae) below the bee's abdomen.

Judging by the images on BugGuide as of January, 2005, Macrosiagon is the most frequently encountered/photographed genus in eastern North America. Perhaps this is due to its fairly large size, typically circa 9 mm.