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A new record of the parasitic beaver beetle (Platypsyllus castoris) from Texas.

Platypsyllus castoris Ritsema (Coleoptera: Leiodidae) is an ectoparasite of the American beaver (Castor canadensis Kuhl) and Eurasian beaver (C. fiber L.) that feeds on host epidermal cells, skin secretions, and possibly blood (Wood 1965). Adult P. castoris beetles are acutely dorso-ventrally flattened (Fig. 1) and can move rapidly through the beaver's dense underfur; this louse or flea-like appearance led to its initial description as a new species of flea (Ritsema 1869). The beetle is somewhat resistant to freezing temperatures and responds quickly to warmth, but is vulnerable to desiccation (Janzen 1963). The ectoparasitic habit of P. castoris is likely derived from a cholevid beetle ancestor which was a scavenger in small mammal nests or burrow systems (Wood 1965; Waage 1979; Peck 2006).

Both larval and adult P. castoris parasitize the host, and the life cycle is unique in that it is completed in its entirety upon the host, save for three brief periods (Wood 1965): gravid females briefly abandon their hosts to oviposit on debris within beaver lodges or burrows where their eggs hatch after ~32 days; emergent larvae subsequently migrate to an available host and undergo three instar stages of development, with mature third-instars leaving the host to pupate in elevated soil of lodges and burrows, and adults emerging after 11-22 days, depending on ambient temperature.


In December 2008, an adult male beaver was trapped by the senior author on the Wichita River, 4.7 km SSE Thornberry, Clay Co., Texas U.S.A. (34' 01' 42" N; 98' 22' 04" W). While skinning the beaver, a large number of P. casloris (75) were noticed moving about on the facial area. After freezing the pelt, specimens were removed using a knit comb and forceps, and were stored in 80 percent ethanol or slide mounted. This discovery led to the examination of other beaver pelts collected by the senior author. Six additional P. castoris specimens were combed from another male beaver collected on the same excursion (stored separately) ca. 12 km downstream of the aforementioned beaver, while none were found on three beavers trapped along the Wichita River in Wichita County. Vouchers were deposited at Midwestern State University, Texas A&M University, Carleton University (Ottawa, Canada), and the entomological collection at the National Museum of Natural History, Smithsonian Institution (assignment of insect accession numbers not practiced by above collections).

In North America, P. castoris is thought to occur on beavers throughout their distributional range, although beetle abundance appears to be higher in the Midwest and northern regions of the United States and lower in the south (Peck 2006). Only two other existing specimens of P. castoris from Texas are known, and both reside in the Texas A&M University (TAMU) insect collection. The TAMU specimens arc labeled "Tex" but unfortunately have no additional data, and it is clear from the style of mounting and general appearance of their labels that they are quite old (E. Riley, pers. comm.). In addition, Leng (1920) also cited "Tex." as a locale for P. castoris, but no further data were given. Other specimens of P. castoris from Major, Payne and Latimer counties of Oklahoma (R. Grantham & E. Riley, pers. comm.) lend additional support for established populations in southern climes. In Texas however, the beetle appears to be either uncommon or unobserved, and it has never been previously seen by the senior author despite many years of trapping beaver within the Wichita River drainage, although admittedly, it would be easy to overlook. This report represents the first record of P. castoris from Texas with both known host and location data.

Although P. castoris is thought to be an obligate parasite of beaver, Belfiore (2006) recently reported a specimen from a river otter (Lontra canadensis Schreber) in California. In Texas, the muskrat (Ondatra zibethicus L.) and the introduced nutria (Myocastor coypus Molina) also seem likely alternate hosts for the beetle; however, no known records of P. castoris from cither species exist, and Lawrence et al. (1961) report that P. castoris did not survive on experimentally infected muskrats.

The high-saline and low-gradient character of the Wichita River precludes many aquatic macrophytes and seems to be generally poor muskrat habitat with negligible evidence of their presence. In north-central Texas, there is only one known record of the river otter (Johnson County), and nutria in the northern Rolling Plains are rare (Schmidly, 2004), with the senior author having observed only three nutria (one on Beaver Creek in Wichita County, and two on the Clear Fork of the Brazos River in Stephens County) in 17 years of canoeing and trapping local riverine areas. Although beaver are common in the area, potential for aberrant P. castoris infestations is probably higher in regions of the state with greater numbers of diverse aquatic mammals. In the northern Rolling Plains of Texas, it appears that P. castoris will likely remain an obligate parasite of the beaver.


We thank Roy Vogtsberger of Midwestern State University for his valuable advice and the use of his laboratory equipment, as well as Ed Riley of Texas A&M University and Richard Grantham of Oklahoma State University for their information on existing specimens. Appreciation is expressed to Jerry L. Cook and an anonymous reviewer for their helpful editorial commentary on the manuscript.


Belfiore. N. M. 2006. Observation of a beaver beetle (Platypsyllus castoris Ritsema) on a North American river otter (Lontra canadensis Schrcber) (Carnivora: Mustelidae: Lutrinae) in Sacramento County, California (Coleoptera: Leiodidae: Platypsyllinae). Coleopt. Bull., 60:312-313.

Janzen, D. H. 1963. Observations on populations of adult beaver beetles, Platypsyllus castoris (Platypsyllidae: Coleoptera). Pan-Pac. Entomol., 34:215-228.

Lawrence, W. H., K. L. Hays & S. A. Graham. 1961. Ectoparasites of the beaver (Castor canadensis Kuhl) [microform series]. Wildl. Dis., 12:1-13.

Leng, C. W. 1920. Catalogue of the Coleoptera of America, north of Mexico. J. D. Sherman, Jr., Publ., ML. Vernon, New York, x +470 pp.

Peck. S. B. 2006. Distribution and biology of the ectoparasitic beaver beetle Platypsyllus castoris Ritsema in North America (Coleoptera: Lciodidae: Platypsyllinae). Insecla Mundi, 20:85-94.

Ritsema, C. 1869. [No title]. Pet. Nouv. Entomol., (Sept. 15). 1:23.

Schmidly, D. J. 2004. The Mammals of Texas, revised edition. Univ. Texas Press, Austin, 501 pp.

Waage, J. K. 1979. The evolution of insect/vertebrate associations. Biol. J. Linn. Soc., 12:187-224.

Wood, D. M. 1965. Studies on the beetles Leptinillus validus (Horn) and Platypsyllus castoris Ritsema (Coleoptera: Leptinidae) from beaver. Proe. Entomol. Soc. Ont., 95:33-63.


Samuel W. kelley and Dana R. Mills

U.S. Geological Survey

Wichita Falls. Texas 76308 and

Department of Biology. Midwestern State University

Wichita Falls. Texas 76308
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Title Annotation:GENERAL NOTES
Author:Kelley, Samuel W.; Mills, Dana R.
Publication:The Texas Journal of Science
Article Type:Report
Geographic Code:1USA
Date:May 1, 2010
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