[Atlantic Canada Coleoptera]

Staphylinidae: Proteininae

The Proteininae are a small subfamily of Rove Beetles (Staphylinidae). The beetles themselves are small, generally less than 3.0 mm in length. They are found in fungi, under bark, in leaf litter and on decaying vegetation where they are believed to by mycophagous or saprophagous (Newton et al. 2001). Only two genera are known in North America, Megarthrus Stephens 1829 and Proteinus Latreille 1796. Species of both genera have been recorded in Atlantic Canada.

Proteinus pseudothomasi Klimaszewski

These beetles are 1.35 mm in length, piceous-brown in coloration throughout. The elytra is finely punctate and setose with sparse, longish setae decumbant along the elytra which is slightly transversely rugose. The last three tergites are exposed by the elytra. The antennae are 11-segmented with a 3-segmented club and are setose throughout. The tarsal formula is 5-5-5. The head is densely reticulate and there are a pair of depressions between the eyes which, however, lack the ocelli that are characteristic of the omaliinae. The eyes are large and are not setose. It was described by Klimaszewski et al. (2005).

I have now found this species in both Nova Scotia and New Brunswick. Newton et al. (2001) reported that Proteinus species are believed to by mycophagous or saprophagous, and sometimes predaceous and are found in decaying fungi, carrion, and plant debris. In Nova Scotia they have been found in forest floor litter in an old hemlock forest whereas in New Brunswick I found them on vegation adjacent to a small, forested brook.

Proteinus pseudothomasi Proteinus pseudothomasi Proteinus pseudothomasi Proteinus pseudothomasi

Proteinus pseudothomasi : Dorsal Habitus

Proteinus pseudothomasi : Dorsal Habitus

Proteinus pseudothomasi : Ventral Habitus

Proteinus pseudothomasi : Head

Megarthrus americanus Sachse

This is a widely distributed beetle in eastern Canada having been recorded from Manitoba, Ontario, Québec, New Brunswick, Nova Scotia, and Prince Edward Island (Campbell & Davis 1991). It is not, however, frequently encountered. Newton et al. (2001) reported that they are saprophagous or mycophagous and are found in leaf litter, rotten wood, fungi, dung, carrion, and flood debris. The one specimen which I have collected on Prince Edward Island was on horse dung on a trail adjacent to a tidal river.

Megarthrus is differentiated from Proteinus via the following key (from Newton et al. 2001):

  1. Pronotum with median longitudinal impressed line, strongly explanate laterally, posterior corners notched; body flat and wide. - Megarthrus Stephens 1829

    Pronotum without imprssed line, not explanate laterally, posterior corners entire; body moderately convex, more narrowly oval. - Proteinus Latreille 1796

The beetles are 2.3-2.7 mm long, dusky in coloration with the head black and legs dull yellow. The pronotum, which is as wide as the elytra is finely rugose; the margins with a small blunt tooth in front of middle and another 1.4 of the way from the base. The pronotum as a longitudinal impressed grove that extends the entire length.

Megarthrus americanus Megarthrus americanus Megarthrus americanus Megarthrus americanus

Megarthrus americanus: Photo Pending

Megarthrus americanus: Photo Pending

Megarthrus americanus: Photo Pending

Megarthrus americanus: Photo Pending


Campbell, M. J. and Davies, A. 1991. Staphylinidae: Rove Beetles. In: Bousquet, Y. Checklist of Beetles of Canada and Alaska. Agriculture Canada Publication 1861/E. pp. 86-124.

Downie, N. M. & Arnett, R. H., Jr. 1996. The Beetles of Northeastern North America. Sandhill Crane Press. Gainsville, Florida. 1721 pp.

Klimaszewski, J., Sweeney, J., Price, J., and Pelletier, G. 2005. Rove beetles (Coleoptera: Staphylinidae) in red spruce stands, eastern Canada: diversity, abundance, and descriptions of new species. The Canadian Entomologist, 137: 1-48.

Newton, A. F., Thayer, M. K., Ashe, J. S., and Chandler, D.S. 2001. Staphylinidae Latreille, 1802 In Arnett, R. H., Jr. and Thomas, M. C. [Eds.] American Beetles, Volume 1: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia. CRC Press, Boca Raton, USA. pp. 272-418.

Many thanks to Max Barclay of the Department of Entomology of the Natural History Museum in London, England and Jan Klimaszewski, of the Laurentian Forest Centre, of the Canadian Forest Service for their assistance.

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