Typocerus serraticornis Linsley and Chemsak, 1976

Typocerus serraticornis Linsley & Chemsak, 1976 is very rare in collections, probably due to its peculiarly unlepturine-like preference for inhabiting xeric, high-altitude grasslands around the Great Basin. The species can be easily identified among our Pacific Northwestern lepturine fauna by the combination of the following characters: elytra black and yellow-striped with humeral angles red; antennae serrate with poriferous areas on outer segments, 12-segmented in males;  pronotum broad, not constricted at base.

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.

Habits
James Robertson (1988) has published an excellent article in which he describes the larvae and pupae of T. serraticornis, and reports the findings from his extensive fieldwork and observations on the behavior and ecology of this anomalous lepturine. The following summary of the life history, ecology and distribution of T. serraticornis is based on that article. Robertson's field sites were in California (Larkin Dry Lake, Mono Co.; Tinemaha Cr., Inyo Co.; 11 mi. W state line on Hwy 167, Mono Co.) and Nevada (Green Springs, 7 mi E of Gabbs, Nye Co.; SE Corner of Smith Creek Dry Lake, Lander Co.).  

Life history and ecology
Unlike its close relative, Typocerus octonotatus, which bores into several species of grass in the plains east of the Rockies, T. serraticornis is only known to utilize a single host plant, the so-called "indian ricegrass" Oryzopsis hymenoides. (The Oregon Plant Atlas lists hymenoides Ricker ex Piper under its generic synonym Achnatherum). Robertson observed that ricegrass will grow in a variety of habitats, including in very dry and rocky soil conditions. However the larvae of serraticornis prefer to inhabit grass growing in looser soil, especially along the shorelines of Pleistocene dry lakes, where sand is allowed to drift and cover the lower portion of the culm. The larvae bore throughout the culm and roots of the plant, never venturing above the level of the sand, which probably protects the the larvae from the typically cold conditions of its high-elevation habitats (see block-quoted paragraph under "Distribution" below). Pupal chambers are constructed over the course of 8 months, and full development from egg to adult may take as many as three or four years. Adults emerge in the later part of May and can be found throughout early to mid June mating and flying around patches of indian ricegrass. Apparently two methods of oviposition are possible (p. 237). In the first, the female gnaws a crack into the stem portion of the culm. This causes the stem above the crack to fall over, creating a cavity in which the egg is deposited. In the second case the female lowers herself into the sand and grass debris at the base of the culm and deposits the egg there. Females hold around 30 eggs and will fly or crawl from plant to plant depositing only one egg per stem.  Females were observed to carry far fewer, and larger eggs than a typical cerambycid. It is presumed that this is a strategy adapted to xeric conditions, as larger eggs (3.12 mm x 1.03 mm) would reduce moisture loss (Robertson, pp. 232, 240).   

Penrose (1979) collecting with R. L. Westcott in SE Oregon report adults visiting flowers of Sphaeralcea grossulariaefolia (Hook. and Arn.) and Eriogonum ovalifolium Nutt. 

Varnish production 
Robertson observed that during construction of the pupal chamber a larval secretion appears to be produced, creating a film which cements together the sand and plant fibers used to create the chamber. Robertson suggested that this was the first known example of silk production in Cerambycidae, "albeit tentative." 

"The material used on the pupal cell wall is laid down as a thin film with infrequent stranding onto the short fibers forming the wall to act as binder, stiffener and protective sheathing. It shows itself as a somewhat glossy surface on the grass fibers and as a fillet radius at the interface of adjoining fibers. SEM photographs of the cell wall are shown in Fig. 31 and Fig. 32. In the rearing cage in once instance, two larvae in close proximity, having started separate cells merged into one. In the ensuing struggle which occurred between the two, both were liberally covered with the same substance and subsequently died. The same situation was found in the field in June of 1987." (p. 240)

Robertson notes that dissections of the larvae and SEM photography of the head, mouthparts, anal opening and Malpighian tubules, in addition to observations of living larvae failed to reveal the origin of the silk or "varnish."

Distribution
Robertson (p. 235, fig. 13) provided a map with the 11 localities of T. serraticornis known from specimens at the time, plus the 3 additional localities he discovered during his field work. Robertson points out that the distribution of the host plant O. hymenoides, which extends throughout eastern Oregon, Idaho and Montana, suggests that additional populations of serraticornis are likely to be discovered farther north than the species' present known distribution. The rainfall, temperature and elevation parameters provided by Robertson (p. 239) for his collecting localities may be useful in predicting additional localities with GIS:

"Published collecting records of T. serraticornis show it occurs from 762m (2500 ft) (Strike Lake, Idaho) to 2745 m (9000 ft) (Rico, Colorado). O. hymenoides has the same upper limit but occurs as low as 425 m (1400 ft) (Fig. 13). I think future collecting in areas further north of those recorded will find beetles at even lower elevations, because of generally lower temperatures. Based on Howden's postulates I do not think that beetles will occur in the southern extremes of the range of the grass at lower elevations because of the barrier of warmer temperatures. When collecting in December, with mid-day temperatures at 8C (47F) ambient, 3.3C (38F) on the ground (with patchy snow) and the ground frozen at 11 cm (4.3'') below the surface, I found larvae actively feeding and constructing pupal cells. The night-time low was -7.2C (19F). Examination of monthly average temperatures/rainfall data for a thirty year period from Fallon, Nevada, at 1250 m (4100 ft) shows a low of -0.4C (31.2F) in January to a high of 22.7C (72.9F) in July, with a steady change of about 4C (7.2F) a month. The direst months are July and August and heaviest rainfall occurs in May, 18.5 mm (.72'' (Rust, 1986). (May of 1987 had a record of 1.71 inches.)"  

So far, only a small handful of populations are known in the Pacific Northwest from southeastern Oregon and southern Idaho. The population at Little Cottonwood Cr. in Southeastern Oregon was reportedly discovered by Rick Westcott and R. Penrose (in Penrose, 1979), however a single specimen recently discovered among the unidentified beetles in the Oregon State University collection (see above figure and caption) predates that discovery by 14 years! 

References

1. Howden, H.F. 1963. Speculations on some beetles, barriers, and climates during the Pleistocene and pre-Pleistocene periods in some non-glaciated portions of North America. Systematic Zoology 12: 178-201.
2. Linsley, E.G. and J.A. Chemsak. 1976. Cerambycidae of North America. Part VI, No.2. Taxonomy and Classification of the Subfamily Lepturinae. University of California Publications in Entomology 80, 186 pp.
3. Penrose, Richard. L. 1979. Notes on three Oregon Lepturine Cerambycidae. Pan-Pacific Entomologist. 55(2): 159-160.
4. Robertson, J. A. 1988. Descriptions of the immatures of Typocerus serraticornis (Coleoptera: Cerambycidae), and new observations on biology, including “Varnish” production and usage by larva. The Pan-Pacific Entomologist. 64(3), 228-242.
5. Rust, R. W. 1986. Seasonal distribution, trophic structures and origin of sand obligate insect communities in the Great Basin. Pan-Pacific Entomologist. 62(1): 44-52.