Lutrochus laticeps Casey, 1893

Gustafson, Grey T., Maier, Crystal A., Baca, Stephen M. & Faris, Christina K., 2014, Rediscovery ofLutrochus laticepsCasey, 1893 (Coleoptera: Lutrochidae) and the Discovery ofDineutus productusRoberts, 1895 andDineutus serrulatus analisRégimbart, 1882 (Coleoptera: Gyrinidae) in Kansas, USA, with Notes on Habitat Preference, The Coleopterists Bulletin 68 (4), pp. 713-718 : 714-715

Lutrochus laticeps Casey, 1893

Lutrochidae is a small family of aquatic dryopoid beetles comprised of 17 nominal species (Maier and Short 2013). The family is endemic to the New World, and members of this group live in rather unique microhabitats as adults and larvae. In the tropics, larvae of Lutrochus Erichson, 1847 develop inside waterlogged woody debris in fastflowing streams and rivers (Valente-Neto and Fonseca-Gessner 2011), while in the temperate regions Lutrochus larvae live in high-calcium streams—a habit which has earned them the common name “the travertine beetles.”

In contrast to their congeners in the Neotropics, which are active year-round, adults of the three North American species are highly periodical, as they are only active during late May to early September. Lutrochus laticeps is widespread in eastern North America, from southern Canada to Missouri and northeastern Oklahoma, and probably has the widest geographic range of any species of Lutrochus ( Brown 1976; Roughley and Larson 1991). Throughout its range, L. laticeps has varied habitat preferences with one thing in common—they prefer to be in the boundary area where fast-flowing water splashes on debris, moss, or rocks. Adult beetles may be found flying around and resting on moist leaf packs and debris dams in rivers and streams (Spavinaw Creek, OK, C. Maier personal observation and museum specimens) and on wave-splashed rocks on the Great Lakes (Put-in-Bay, OH, museum specimens). These habits are similar to those of Psephenus herricki (DeKay, 1844) (Psephenidae) , and the two are often collected together. The closely related species, Lutrochus arizonensis Brown and Murvosh, 1970 and Lutrochus luteus LeConte, 1852 , have been reported from similar habitats in Arizona and Oklahoma, respectively (Brown and Murvosh 1970; Reisen 1977). The bedrock in these habitats is almost always limestone, and travertine deposits are common.

The existence of L. laticeps in Kansas is not surprising, as it is relatively abundant in the appropriate habitats and at the right time of year in Missouri and Oklahoma. However, despite extensive sampling of Kansas rivers and streams by entomologists at the University of Kansas (KU) and the Kansas Biological Survey (KBS) (2,058 collecting events for aquatic Coleoptera in Kansas as of 2 June 2014), no specimens of L. laticeps were obtained. The only known record of L. laticeps from Kansas is a single specimen collected in 1920 from Neosho County by Dr. William E. Hoffman, former Assistant Curator of Entomology at KU (CReAC 2014). The specimen had no further locality or habitat information, which is typical as the unique habitat preferences of L. laticeps prevent it from being collected in both general benthic samples and with terrestrial collecting methods. For example, intense benthic sampling by four collectors in typical riffle and run habitat below Elk Falls (Elk Co., Kansas) yielded a variety of aquatic beetles, including several species of Stenelmis Dufour, 1835 (Elmidae) and Gyretes Brullé, 1835 (Gyrinidae) , but no L. laticeps . Once the appropriate habitat was found at Elk Falls, travertine beetles were present in great abundance.

The Elk River at Elk Falls is located in a riparian woodland surrounded by corn/wheat/soybean farmland at the edge of the Flint Hills in Elk County, KS ( Fig. 2A ). The waterfall (N 37.374416°, W 96.184123°) is formed at the edge of a Shawnee Group limestone formation where it erodes the neighboring shale. The rock at the falls is covered in dense green algae, and ample log jams from woody debris and rubble are present ( Fig. 2B,D ). Lutrochus adults were found taking shelter and grazing on algae and moss ( Fig. 2C ) on the water-splashed vertical rock faces immediately at the falls, nestled in crevices in algae-covered logs, and in wet (but not submerged) leaf-packs. Ten specimens were collected at this site during 22 June 2014, however, sampling immediately down- and upstream in slower moving riffles and runs did not produce any specimens .

Figures

Fig. 2. Elk Falls, habitat. A) Pointer indicates area of falls where Lutrochus laticeps was found, B) Pointer indicates microhabitat of L. laticeps, C) Pointer indicates L. laticeps in moist moss, D) G. Gustafson and C. Faris collecting L. laticeps from falls.