Pionacercus is one of the watermite genera that resemble Piona genera, but differ in having only three acetabula on each of the two genital plates. Other genera like that are Tiphys and Pionopsis. Pionacercus vatrax is found in Europe and rather common in the Netherlands in spring (Smit & van der Hammen, 2000). The female specimen presented here was found in may 2015 in a small, slowly flowing canalised stream which wasn't very clean, near the city of Deventer.
With its small size (0.85 millimeters) this watermite was a rather inconspicuous little dot between the lumps of algae and detritus. With a loupe the appearance is as on the picture at left. On the top side of the mite, the bright yellow stain of the excretory organ remind of that of Forelia, but on that species the dark patches are not as broad. Only the underside shows the typical characteristics of Pionacercus.

Pionacercus vatrax is a species of ditches and normalised brooks, with enough plants and moderate eutrophic water, according to literature (Smit & van der Hammen, 2000). The stream mentioned appeared to match that description. At the time of sampling the water was shallow and there were lots of tadpoles. Below are two pictures of the stream, the mite was caught in the part shown on the right picture.

Click on the picture below for the next page.

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