Description: Antennae 11-segmented with a distinct, 2-segmented club (rarely antennomere 9 expanded apically, causing club to appear 3-segmented). Antennal setation sparse. Subantennal grooves greatly reduced to a small depressed area or absent. Eyes large, well-developed, finely to coarsely faceted, nearly always with obvious interfacetal setae. Antennal segment 3 slightly elongate (only slightly longer than 4) Pronotal disc carinate, with at least 2 pairs of longitudinal carinae, lateral margins (in most) slightly to strongly explanate, serrulate to denticulate. Pronotum usually wider than long. Procoxal cavities open. Metacoxae narrowly separated, separation less than metacoxal length. Tarsal formula 4-4-4. Dorsal surface consisting of thin, fine, hair-like setae (rarely clothed in velvet-like setae).
Similar genera: The genus Bitoma is similar in general appearance to Microprius, Paha and Lasconotus. In Microprius, the antennal groove is long and reaches to the posterior margin of the eye. Bitoma differs from Paha and Lasconotus in having a 2-segmented antennal club (1-segmented in Paha and 3-segmented in Lasconotus). In Lasconotus, the procoxal cavities are closed.
Northeast (VA, WV, MD, DE, NJ, NY, CT, MA, NH, VT), North Central (IA, MO, IN, OH), Southeast (NC, SC, TN, GA, AL, FL), South Central (TX, OK, MS), Northwest (OR, WA, ID), Southwest (NM, AZ, CO, NV, CA) USA; Ontario, Canada.
Bitoma has been collected at MV/UV lights and from injured or dead cacti (B. gracilis), in leaf axils of dying agave and yucca (B. gracilis), in the nest piles of packrats (B. gracilis, B. sulcata), in flood debris (B. ornata), and under the bark of dead hardwoods and pines, including: mesquite and palo verde, sotol (B. neglecta, B. gracilis), cottonwoods (B. sulcata, B. ornata), maples (B. ornata, B. quadricollis), pines (B. pinicola), oaks (B. quadricollis, B. sulcata, B. carinata), and beech (B. quadricollis).
Abundance: some species are common.
North American Species (14)
Bitoma brevipes (Sharp, 1894)
Bitoma carinata (LeConte, 1863)
Bitoma crenata (Fabricius, 1775)
Bitoma discolor Schaeffer, 1907
Bitoma exarata (Pascoe, 1863)
Bitoma gracilis Sharp, 1894
Bitoma granulata (Blatchley, 1910)
Bitoma ornata (LeConte, 1858)
Bitoma neglecta Stephan, 1989
Bitoma pinicola Schaeffer, 1907
Bitoma quadricollis (Horn, 1885)
Bitoma quadriguttata (Say, 1826)
Bitoma sulcata (LeConte, 1858)
Bitoma vittata Schaeffer, 1907
Bitoma quadriguttata (eastern) and B. ornata (western) are, by far, the most abundant species.
Bitoma brevipes: Eastern species. B. brevipes can be readily distinguished by the dark, cylindrical body, pronotm distinctly longer than wide, with 2 pairs of well-defined, full-length, slightly curved to sinuate carinae and an additional pair of short carinae anteromedially, and reduced interfacetal setae. This species can be separated from the similar B. carinata by the additional short pair of carinae on the anterior portion of the pronotal disc and less granulate pronotum. Distribution: Known from Fort Meyers, Florida, although this is probably an introduction. B. brevipes is known from Mexico, Panama, and Costa Rica. This species may also occur in the Southwest USA and it is unclear whether or not this species has been established in the United States.
Bitoma carinata: Eastern species. B. carinata can be readily distinguished by the dark, cylindrical body, pronotm distinctly longer than wide, distinctly granulate with 2 pairs of well-defined, full-length, slightly curved to sinuate carinae, and reduced interfacetal setae. This species can be separated from the similar B. brevipes by the lack of an addition short pair of carinae on the anterior portion of the pronotal disc and more granulate pronotum. Distribution: Alabama, Florida, Georgia, Mississippi, South Carolina, Virginia, USA.
Bitoma crenata: Eastern species. This species can be distinguished by the large red spots and apically enlarged 9th antennal segment, causing the antennal club to appear 3-segmented. B. crenata most closely resembles B. sulcata, but can be separated by the more smooth central area of the pronotal disc, eyes flattened and not nearly as protruding, reduced to absent interfacetal setae, generally bi-colorous body, and geographic distribution. This species is locally common. Distribution: Indiana, New York, Ohio, Vermont, Washington, USA; Ontario, Canada. This species has been introduced from Europe (apparently twice).
Bitoma discolor: Eastern species. B. discolor can be distinguished from other Bitoma by the larger eyes with dense, stout, curved interfacetal setae, larger antennal club, and distinctly denticulate lateral pronotal margins. This species is most similar to the more common B. quadricollis, and can be separated by the dark elytra with lighter spots and geographical distribution. This species is rare. Distribution: southern Florida and the Florida Keys, USA. This species is also found in Cuba.
Bitoma exarata: Western species. The larger size and distinctive dorsal ornamentation consisting of carinae and granules clothed in velvety scales (tomentose) should adequately distinguish this species. Distribution: extreme southern Arizona, USA. This species also occurs from Brazil to Mexico.
Bitoma gracilis: Western species. Most similar to B. neglecta, but differs in having a sparsely setose/glabrous prosternum, eyes set closer apart ventrally, narrower pronotum, more elongate, generally lighter in color and smaller in size. Distribution: Arizona, California, New Mexico, Texas, USA.
Bitoma granulata: Central/eastern species. B. granulata can be easily separated from the remaining North American Bitoma by the greatly reduced eyes and the extremely flattened body. This species is extremely rare. Distribution: Missouri, Indiana, Iowa, USA.
Bitoma ornata: Western species. Most similar to the introduced B. crenata, but differs in the smaller 9th antennal segment. This is the only native western species with red spots. Distribution: Arizona, California, Idaho, Nevada, Oregon, Colorado, USA.
Bitoma neglecta: Western species. Most similar to B. gracilis, but differs in having a setose prosternum, eyes set farther apart ventrally, wider pronotum, less elongate, generally darker in color and larger in size. Distribution: Arizona, USA.
Bitoma pinicola: Eastern species. This species can be separated from all other eastern species by the larger size, greatly flattened body, and widely separated eyes (ventrally). Distribution: Delaware, Massachusetts, New Jersey, North Carolina, USA.
Bitoma quadricollis: Eastern species. B. quadricollis can be distinguished from other Bitoma by the larger eyes with dense, stout, curved interfacetal setae, larger antennal club, and distinctly denticulate lateral pronotal margins. This species is most similar to the rarer B. discolor, and can be separated by the unicolorous elytra and geographical distribution. This species is uncommon. Distribution: New Jersey, Maryland, Ohio, Florida, Mississippi, North Carolina, Tennessee, West Virginia, Virginia, Oklahoma, USA.
Bitoma quadriguttata: Eastern species. This species varies widely in coloration, and is most often confused with B. quadricollis, B. granulata (darker specimens), and B. gracilis, B. discolor (redder specimens). Dark B. quadriguttata can be distinguished by the size and position of the eyes. B. quadriguttata can be distinguished from B. gracilis by the less narrow body, eyes closer together ventrally, and inner pair of pronotal carinae curved outward. B. quadriguttata can be distinguished from B. discolor by the more well-separated eyes ventrally and more granulate prosternum. Distribution: Connecticut, Delaware, Indiana, Maryland, New Jersey, New Hampshire, New York, Ohio, Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, Tennessee, West Virginia, Virginia, Oklahoma, Texas, USA; Ontario, Canada. This is by far the most commonly encountered North American species of Bitoma.
Bitoma sulcata: Western species. This species can be distinguished by the apically enlarged 9th antennal segment, causing the antennal club to appear 3-segmented. B. sulcata most closely resembles B. crenata, but can be separated by the more rugose and setose central area of the pronotal disc, eyes rounder and greatly protruding, interfacetal setae more prominent and dense, generally uni-colorous body, and geographic distribution. This species is locally common. Distribution: Arizona, California, Texas, USA.
Bitoma vittata: Western species. B. vittata can be immediately distinguished from the other North American Bitoma by the lateral margins of the pronotum greatly explanate and distinctly narrowed basally. This species is uncommon. Distribution: extreme southern Texas, USA.
On a regional level, the genus Bitoma appears stable, although the defining characters break down on a worldwide scale. The overall generic concept is still in question, with many aberrant forms currently included in this large, cosmopolitan genus. A worldwide revision of the genus and a closer investigation of the generic definitions of the genera within the tribe Synchitini is the only way to resolve this issue.
Potential Problems with Identification
The North American species within this genus all appear very similar and will be hard to differentiate without a synoptic collection. Most of the species are rarely encountered. If identification is uncertain, it is suggested the specimens are checked against the most common species for that particular geographic region. Teneral specimens are much paler in color and may not exhibit the standard patterns of coloration diagnostic for the species.