Chaetarthria seminulum - microcosmos.nl

Chaetarthria cf. seminulum

Like many other species of Water Scavengerbeetles, Chaetarthria occasionally crawls with its belly up close to the water surface to bring its underside into contact with the air above water. This can be seen in the photo above left. In this way it refreshes the air supply on its belly, which is held there by a layer of water-repellent hairs. It will be clear that the effect of the surface tension is much more noticeable for an insect of 1.5 mm than for us: we cannot pull such a 'dimple' in the surface.

In the picture on the bottom left, the beetle has a somewhat clumsy grip on a stem. In the picture on the bottom right, one of the antennae is extended. It looks grey because of a covering of water-repellent hairs. All spinning water beetles use their antennae to create an air channel at the water surface in order to refresh their breathing air. The advantage over the 'belly sliding' described above is probably that it can be done much more stealthily, between some duckweed leaves, for example.

Strange name, Chaetarthria: can be broken down into chaet- : hair, brush and arthria, which can mean both artery (vein, air tube) or joint. "Joints with brushes" sounds logical, but this beetle has a strange, somewhat tubular cavity under the abdomen with a fringe of hair, with a pair of peculiar, gelatinous deposits behind it. Were these perhaps seen as the 'hairy arteries'? If anyone knows, please email it to me... seminulum means, I think: seed grain

It was recently discovered that there are not one, but three species of Chaetarthria in the Netherlands. First, C. simillima was found and later C. similis. The three species can only be distinguished after dissecting the beetle and microscopy of the sexual organ (Cuppen&Vorst,2003). That is why I have put a cf. abbreviation in the name: I can no longer say with certainty that this is C. seminulums.

Bibliography: (See also the Waterbeetle bibliography)

Cuppen, J. & Vorst, O. 2003 A third Palearctic species of Chaetarthria STEPHENS (Coleoptera: Hydrophilidae) Koleopterologische Rundschau 73 161-167 Wien 2003
Read 2008, as an announcement on http://macrofauna.web-log.nl/macrofauna/2004/08/macrofaunanieuw_38.html
Retrieved 22-08-2024 from https://www.zobodat.at/pdf/KOR_73_2003_0161-0167.pdf

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