Cylindroselloides dybasi

Cylindroselloides dybasi in the Maritime Provinces

Cylindroselloides dybasi in polypore.

Introduction

The world is filled with an astonishing variety of beetles. Over 350,000 species have been described. These vary in size from Titanus giganteus (Linné) a longhorn beetle from the jungles of northern Brazil and French Guiana, which grows up to 20 centimeters in size to the smallest of the Feather-winged Beetles (Ptilidae), Nanosella fungi LeConte which tips the bottom of the scale at 0.25 mm in length.

There are a 29 species in the family Ptiliidae found in Atlantic Canada (Majka & Sörensson, 2007) but only one species of the minuscule Nanosellini, Cylindroselloides dybasi Hall. Hall (2000) provides an excellent review of the family in North America.

Nanosellini

Cylindroselloides dybasi on H. annosum..

These tiny beetles (they are in the tribe Nanosellini; the term nano originating from the Greek word nannos, meaning dwarf; now employed in the term nanometer which is one billionth of a meter) are comparatively little known and studied since they are so tiny that they frequently pass unnoticed. In the past couple of years collecting in many areas on Nova Scotia, New Brunswick, and Prince Edward Island has revealed that they are abundant in many suitable habitats.

With the exception of one species (there are eight genera and ten species found in North America) all Nanosellines are found in and on the undersurface of woody mushrooms of the Families Polyporacae and Hydnacae. The most familiar of these are Polypores, so-called bracket-or shelf-fungi. Their tiny size makes it possible for them to live inside the tubes of Polypores where they feed on fungal spores and hyphae. Both adults and larvae inhabit this environment. Careful examination of such fungi with a hand lens may enable you to find these miniscule beetles.

Cylindroselloides dybasi Hall

Cylindroselloides dybasi on H. annosum..

The species pictured in these photographs (photographed in Nova Scotia, Canada) is Cylindroselloides dybasi Hall, described by Eugene Hall (Hall 1999) and named in honour of Henry Dybas, a pioneer investigator of the the Feather-winged beetles.

The photographs (select any of the thumbnails to see a full-sized version of the photograph) show C. dybasi in and on living Conifer-base Polypore, Heterobasidion annosum. They are about 0.6 mm in length and 0.15 mm in width and are quite active moving in and out of the polypore tubes and interacting with one another. In some instances all you can see if the pygidium (the tip of the abdomen) projecting from the end of a Polypore tube.

Note that they inhabit only living and growing Polypores, and not those, which are dead or have started to decay (a whole different suite of beetles are found in such environments).

References

Hall, W.E. 2000. Ptiliidae Erichson, 1845. In Arnett, R.H., Jr. & Thomas, M.C. [Eds.] American Beetles, Volume 1: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia. CRC Press, Boca Raton, USA. pp. 233-246.

Hall, W.E. 1999. Generic revision of the tribe Nanosellini (Coleoptera: Ptiliidae: Ptiliinae). Transactions of the American Entomological Society, 125(1-2): 29-126.

Majka, C.G. and Sörensson, M. 2007. The Ptiliidae (Featherwing Beetles) (Insecta: Coleoptera) of the Atlantic Maritime Ecozone. In: D.F. McAlpine and I.M. Smith [Eds.] Assessment of Species Diversity in the Atlantic Maritime Ecozone. National Research Council of Canada. Ottawa, Ontario. (in press).