In a small peat ditch I found a couple of dark coloured watermites. The largest specimen was this 2 mm sized mite, that had a striking, lighter red brown spot on the dark body. It appeared to be a female of Tiphys ornatus, according to Besseling (1964) and also according to Viets (1936), who described the species as Acercus ornatus, a name no longer used. The other mites were other species.
Tiphys ornatus is a common species in the Netherlands (Smit & van der Hammen, 2000), and can be found in Europe and Asia (Viets, 1936). It is described in older literature under several genus names. The species is most abundant in spring, Piersig (1897) mentions that the (much smaller) males have almost disappeared after spring and so does Viets (1936), who describes the mating with a drawing: the male is suspended below the female. But it doesn't clamp her legs in the way that Piona species do, instead of the typical cavities in his hind legs of Piona males a part of these leg is broadened and flattened.
The body is shaped like a egg with a narrow tip. The back side is also quite narrow, as is
visible on the somewhat blurred picture on the left, so the outline is an ellipse. According
to Piersig (1897) this is typical for the younger specimen.
Tiphys ornatus looks like a dark brown version of Pionopsis lutescens. Streble &
Krauter (1978) describe that species as Acercopsis lutescens and below that paragraph
I found Tiphys ornatus as a short, separate item. And on Yann's website hydracina.org
I found a watermite which he describes as Pionopsis lutescens but looks to me like
Tiphys ornatus.
The legs of this watermite have swimming hairs and indeed it could swim rather well, but most of the time it crawled around on the bottom or was sitting still. This behaviour was also described by Piersig (1897), who added that the males on the contrary do swim fast and long.
From Tuzovsky (2011) we get details on the development: the larvae can survive the drying-up of the pools they live in and he found deutonymphs in water below melting ice, which could prove the species hibernates in the deutonymph stage.
REFERENCE LIST
Tuzovsky, P.V. (2011) Water mites of the genus Tiphys Koch, 1836 (Acariformes: Pionidae)
in Russia. Acarina 19 (2): 113 - 212. Institute of Biology of Inland Waters, Russian
Academy of Sciences, Borok, Yaroslavl Province, 152742 Russia
Retrieved from http://insects.ummz.lsa.umich.edu/ACARINA/PDFS/2011_2/Tuzovsky2011.pdf
See also the REFERENCE LIST watermites.
LINK: A Pionopsis lutescens on Yann's hydracarina.org that I think is more a Tiphys ornatus.