October 2, 2012 3 Comments
Rewind back to Day 2 of this year’s Annual Fall Tiger Beetle Trip at Gloss Mountain State Park in northwestern Oklahoma—these were actually the first non-Missouri beetles that I photographed on the trip. Crossidius pulchellus is a longhorned beetle (family Cerambycidae) that occurs commonly on flowers of broom snakeweed (Gutierrezia sarothrae) and relatives throughout the Great Plains and southern Rocky Mountains.
I find it rather ironic that Crossidius pulchellus was the first western beetle that I encountered, since my original plans for this year’s late-season trip centered on looking specifically for longhorned beetles in the genus Crossidius (see last year’s Crossidius coralinus fulgidus for an extraordinarily beautiful representative of this genus). Unlike the vast majority of the family that develop as larvae in dead wood, species in this diverse, exclusively western North American genus bore through the roots living, perennial shrubs belonging to the genera Gutierrezia, Chrysothamnus/Ericameria, and Haplopappus (family Asteraceae)—the “goldenrods” of the west, they bloom in widespread, yellow-flowered profusion as summer turns to fall. A wide variety of insects are attracted to these blooms, most of which—bees, flies, wasps, moths, etc.—are opportunistic pollinators. Crossidius beetles, however, are intimately associated with the plants, seemingly spending their entire, brief adult lives either perched, feeding, or mating upon the flowers. Even at night, rather than leaving the plants to search for protected hiding spots, they simply bury themselves deeper amongst the flowers and await the next morning’s first, warming rays of sunlight.
Sampling the diversity of Crossidius that springs forth each year across the west requires carefully timed travel to multiple localities spread widely across rough terrain. As longhorned beetles go, the genus exhibits an astounding level of polytopism (geographically-based variation) that in many respects resembles that exhibited by North American tiger beetles. This has resulted in the description of a relatively large number of species, most of which can be further divided into numerous recognizable subspecies and even local morphs. The discontinuous distribution of their host plants across the broken western topography and resulting isolation of local populations have contributed to this variability, further complicated by hybridization among species occurring together in a given locality (Linsley & Chemsak 1961). I got a taste of the diversity of these beetles during last year’s fall tiger beetle trip as I looped through Colorado, Idaho, and Utah. Although my plans to look for them this year didn’t work out, my appetite remains whetted. There is always next year!
Linsley, E. G. & J. A. Chemsak. 1961. A distributional and taxonomic study of the genus Crossidius (Coleoptera, Cerambycidae). Miscellaneous Publications of the Entomological Society of America 3(2):26–64, 3 color plates.