The Lepturini genera Anoplodera, Grammoptera and Leptura were present in the Oligocene-era fossil beds in Florissant, Colorado. (Linsley, 1958, p. 302, table III).
References
Typocerus LeConte, 1850 is a diverse genus comprising 15 species and several subspecies, all of which except one are found in the eastern half of North America. The only known western species, T. serraticornis Linsley and Chemsak, feeds on Indian ricegrass (Oryzopsis hymenoides) and is found along the shorlines of dry lakes in the Great Basin region, extending into southeastern Oregon and southern Idaho. T. serraticornis and the eastern North American T. octonotatus are among a very small handful of cerambycids known to use grass as a host plant (see Robertson, 1988). The host plants for the majority of Typocerus species remain unknown at present, while the rest utilize either decaying Pinus (for T. zebra, T. sparsus, T. lunulatus lunulatus, and T. lugubris) or a hardwood (in the case of T. velutinus velutinus) for their larval hosts (Linsley and Chemsak, 1976).
Diagnosis. - Typocerus is set apart from other lepturine genera primarily by the characters of the pronotum and antennae. In both Typocerus and Leptura the base of the pronotum is broad and unconstricted. Other genera that superficially resemble Typocerus, such as Xestoleptura, Strophiona and Stenostrophia, have a constriction at the base of the pronotum near the elytra, making the pronotum appear almost spherical from above. Also, the antennal segments in Typocerus tend to be expanded apically, a trait that is most pronounced in T. serraticornis. The outer antennal segments of all Typocerus species bear sizeable depressions, referred to as "poriferous areas", which serve to distinguish the genus from Leptura.
Typocerus serraticornis Linsley & Chemsak, 1976 can be easily identified among our Pacific Northwestern fauna by the combination of the following characters: elytra black and yellow-striped with humeral angles reddish; antennae 12-segmented, serrate, with poriferous areas on outer segments; pronotum broad, not constricted at base. Found on its host plant, indian ricegrass (Oryzopsis hymenoides), from SE Oregon to New Mexico . Penrose (1979) collecting with R. L. Westcott report adults visiting flowers of Sphaeralcea grossulariaefolia (Hook. and Arn.) and Eriogonum ovalifolium Nutt.
Above Figure: T. serraticornis, female. The only specimen in the Oregon State Arthropod Collection was found on May 29, 1965 at Cottonwood Cr., Pueblo Mtns., Oregon. (Collector not recorded). Specimen ID: 613179.
Biology
Flower-visiting lepturine species vary in their foraging habits from being highly generalist to confining their preferences to one or two flower species. Both extremes exist within the genus Typocerus. On one end, the eastern T. velutinus velutinus (Olivier) appears to be one of the more adventurous flower-feeders in Lepturinae. It is also one of the longer lived. Bond and Philips (1999), who surveyed lepturine phenology and feeding behavior over four years in Ohio, suggested that both of these traits--long life and a generalized diet--could be related to the impressive abundance of T. velutinus observed in their field sites. In one week in June, at a single meadow in Ohio, Bond and Philips observed 16 species of lepturines each foraging on an average of 9.38 different species of flowers. T. velutinus, which utilized the maximum number of 16 different species also accounted for 31% of all specimen observations. The correlation between abundance and diversity of flower choice was also positive for the six other most abundant lepturines. At the same field site, Typocerus acuticauda Casey and T. lugubris (Say) were also encountered. T. acuticauda was seen visiting 5 species flowering plant, while T. lugubris only occurred on three flowers, goatsbeard (Aruncus dioicus [Walt]), smooth sumac (Rhus glabra L.), and wild hydrangea (Hydrangea arborescens L.). Several other lepturines at the site showed a statistically significant preference for goatsbeard and wild hydrangea. Interestingly, Bond and Philips (p. 276) point out that even when both goatsbeard and T. velutinus were abundant at the field site, velutinus was not observed visiting goatsbeard once.
Typocerus species can also be generalists in their use of larval host plants. Larval T. velutinus velutinus have been reported from a range of hardwood genera (Quercus, Carya, Betula and Populus are listed by Linsley and Chemsak, 1976). The Pacific Northwestern T. serraticornis however falls on the opposite side of the spectrum from its eastern counterparts since it has developed an obligatory host relationship with a living prairie grass, Oryzopsis hymenoides. The development of specialized, obligatory host relationships within Cerambycidae as a whole is fairly rare, but it was pointed out by Linsley (1959) that it does tend to occur when the host plant utilized is living. The eastern species Typocerus octonotatus is also specialized to bore into living prairie grass. However octonotatus is not confined to a single species. Wade (1922) first reported the habits of this species (incorrectly identified as T. sinuatus Newman) as a forage pest in Kansas. The host plants known for octonotatus are Andropogon scoparius (Little bluestem), Sporobolus airoides (bunchgrass), Sorghastrum nutans (Indian grass), and Agropogon smithii (Colorado bluestem).
The open prairie habitats of octonotatus and serraticornis are anomalous in the Lepturinae. T. serraticornis, which tends to be found on the historic shores of Pleistocene dry lakes around the Great Basin, usually occurs at elevations from 2500 to 9000 ft. and appears to be cold-adapted. A fascinating and detailed account of the habits, ecology and distribution of serraticornis is given by Robertson (1988), who also described its larvae and pupae. Its biology is discussed further on the serraticornis species page.
Updates on Typocerus biology.- New host plants and flower records are recorded for several eastern species by MacRae and Rice (2007). An interesting story was also published on Ted McRae's internet blog about searching for the rare Typocerus deceptus in Missouri.
Remarks on Taxonomy
The type species for Typocerus is T. zebra (Olivier), which is found predominantly in the southeastern United States (range map: Linsley and Chemsak, 1976: p.73, fig. 18).
Our Pacific Northwestern species Typocerus serraticornis bares a remarkable similarity in form and coloration to the European Leptura aurulenta Fabricius. The characters shared by the two species are the shape of the pronotum, the antennal segments expanded at the apices, and the red pigmentation on the humeral angles of the elytra.
Works Cited