ANYONE WHO TOOK A PEEK IN A CLEAR DITCH HAS SEEN THEM: the little red spiders, that swim in the beautiful contrasting green of the waterplants. They seem to roam about aimlessly, like simple red little balls with sprawling legs. Yet there are smaller species, not coloured red, but inconspicuous green or pale yellow. And you have to be an attentive observer to distinguish these minuscule dots in a jar full of jumping waterfleas, where they move in more or less steady tracks, like planets between sparkling stars.

Worldwide there are over 5000 watermite species, with large differences in shape and habits. Some species are very similar to species on land. They are all active hunters. The development from egg to adult is complex and fascinating, often there are six distinct stages, some of these parasitic: the little red bulbs you might have seen on some insects.

Anystis baccarum ? 14-06-2011
enlarge Anystis baccarum ?
an anystid landmite

Somewhere in the development of taxonomy the watermite families were swept together in a suborder called Hydrachnida, Hydrachnidia or Hydrachnellae. Those names are contractions of Hydro: water, arachnida:spider, so they mean simply: waterspiders, or little waterspiders (‑ellae). The suborder was also called Hydracarina in which sometimes the sea mites Halacaridae were included. But this suborder is too artificial according to the more contemporary sources I read (see below); because of their close resemblance to some species on land, they were placed with these species in a suborder called Anystina. You may compare the land mite on the picture at right with for example the very similar Hydryphantes.
I must add that the classification I described is absolutely not the only one around, and might be changed in the future. To get an idea you could follow the links on taxonomy below, to the pages I studied for this information.

Please note: the next article is about complicated matters and might bore you. It is only meant for those interested in taxonomy. Feel free to skip to the next page.

mites table 1 Full scheme: click the picture
On the Taxonomy page I constructed a scheme based on what I have read on Fauna Europaea, Wikipedia and v.d. Hammen (1972). It's not a complete scheme, it may contain mistakes and I made it only to show you a possible watermite classification.
Watermites are placed within the arthropods phylum (Arthropoda), the taxonomy of arthropods has been changed a lot, in fact it still is changing. And there is not one system, because different authors have different opinions.

A part of the scheme is shown below. All mites are placed in a giant group: the Acarina (Mites). This group is a part of the class Arachnidae (spiders and spiderlike animals). There are many mite families, lots of systems were constructed for their taxonomy, and there has been a lot of shuffling within these systems...

Infraclasse Acarina (Acarida, Acari)  MITES A.O.
(Actinedida, Trombidiformes)
Moss mites
Ticks a.o.
(8 superfamilies)
26 super-
and 10 other
Ticks a.o.

The Halacaridae of the superfamily Halacaroidae are sea mites (literally: saltmites). A few species of these live in sweet water. They are small mites (0,5 mm or less) with a peculiar appearance.

Some of the Oribatidae species may also be found in pond and stream, for example those of the Hydrozetes family. They are small, globular mites of a red brown colour, that crawl around slowly on waterplants, duckweed or moss.

The scheme shows how the watermites are close to the ticks. Even closer are other unwelcome guests like the cheese mite, the house dust mite and the scabies mite Sarcoptes scabiei, after which the superfamily Sarcoptidae was named (also described as the order Sarcoptiformes). These mites bear only a vague resemblance to spiders, most of them are microspic lumps with very short legs.
Trombidiform means: clot shaped. (remember: thrombosis). Like ticks, the Trombidiform land and watermites are parasititizing too (as the also used cohortname Parasitengona indicates). But, unlike the ticks, the adults don't drink blood, but the larvae attach themselves to a host to dissolve some of it's tissue and drink that. The Harvest mite is known for it's chiggers, that can sometimes be abundant in late summer, they jump on mammals and may cause Trombiculosis, especially on dogs.

Watermites are NOT dangerous for humans and other mammals: as a rule they only use other arthropods as a host. See page 3 for more.

Watermite.org Site of European watermite researchers
Watermites of North America (University of Arkansas) project, with pictures.
Hydracarina.org Yann's watermite site with many pictures.
Watermite portraits by Wim van Egmond.
Watermite at waterworld.nu
Main source for the table on this page: Fauna Europaea (2010) Fauna Europaea version 2.4. Web Service,
  available online: http://www.faunaeur.org
Other systems:
Species 2000 with a tree structure.
Het NEDERLANDS soortenregister (Dutch register of species) with a tree structure.

About afflictions caused by LAND mites en ticks:
 Trombidiosis on Wikipedia, about the chiggers (larvae) of the Harvest mite.
  An example of the bite wounds of chiggers.
  Ticks and Lyme disease (Department of Health, New York).
  Life-cycle Argasidae on the CVBD website (Canine Vector-Source Diseases). About a family of soft ticks with species that live on birds, bats and other warm blooded animals.

REFERENCE LIST: (See also some specific literature on other pages)

Besseling, A. J. (1964). De Nederlandse watermijten (Hydrachnella Latreille 1802). Amsterdam. Monographieën van de Nederlandse Entomologische Vereeniging No. 1

Davids, C. (1979). De watermijten (Hydrachnellae) van Nederland. Levenswijze en voorkomen. Wetensch. Meded. K N N V, 132, 1-78.

Gerecke, R (editor) 2007. Chelicerata: Araneae, Acari I. Süßwasserfauna von Mitteleuropa7/2 (1): 14-388. Spektrum Akademischer Verlag 2007

Gerecke, R. (editor) 2010. Chelicerata: Acari II. Süßwasserfauna von Mitteleuropa7/2 (2): 1-236. Spektrum Akademischer Verlag 2010

v.d. Hammen, L. (1972). Spinachtigen - Arachnidea IV Mijten - Acarida Algemene inleiding in de acarologie. Wetenschappelijke mededelingen K.N.N.V. nr. 91 march 1972

Neuman, C.J. (1879). Om Sveriges Hydrachnider. Kongl. Svenska Vetenskaps-Akademie Handlingar Bandet 17 № 3. Retrieved from http://archive.org/details/omsverigeshydrac00neum

Piersig, R. (1897). Deutschlands Hydrachniden. Stuttgart. Zoologica 19 (22). 588. Retrieved from http://www.archive.org/details/zoologischerjahr1899staz

Smit, H. & Van Der Hammen, H. (2000). Atlas van de Nederlandse watermijten (Acari: Hydrachnidia). Nederlandse Faunistische Mededelingen,13, 272pp. Retrieved 23 june 2010, from http://www.repository.naturalis.nl/document/45797

Smit, H., van Maanen, B.,van den Hoek, T.H., & Wiggers, R., Knol, B. (2003). New records of rare water mites from the Netherlands (Acari: Hydrachnidia). Nederlandse Faunistische Mededelingen, 25-2003, 123-135. Retrieved from http://www.repository.naturalis.nl/document/46363

Smit, H., van den Hoek, T.H., & Wiggers, R. (2006). Nieuwe vondsten van watermijten in Nederland (Acari: Hydrachnidia). Nederlandse Faunistische Mededelingen, 25-2006, 33-38. Retrieved from http://www.repository.naturalis.nl/document/159674

Smit, H., Hop, H., & Munts, R. (2008). Twee soorten watermijten nieuw voor de Nederlandse fauna, alsmede nieuwe vondsten van zeldzame soorten (Acari: Hydrachnidia) Nederlandse Faunistische Mededelingen, 28-2008, 41-47. Retrieved from http://www.repository.naturalis.nl/document/159615

Streble,H & Krauter, D (1973) Das Leben im Wassertropfen. Kosmos Gesellschaft der Naturfreunde. Franckh'se Verlagshandlung Stuttgart 1978. (p. 96-98, p. 314-319).

Tohru, Uchida. (1932). Some ecological observations on watermites. Contribution no 23 from the Zoological Institute, Faculty of Science, Hokkaido Imperial University.
Retrieved from http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/26941/1/1(4)_P143-165.pdf

Viets,K (1936). Wassermilben oder Hydracarina (Hydrachnellae und Halacaridae). Spinnentiere oder Arachnoidea VII. In: F. Dahl, Die Tierwelt Deutschlands 31 & 32

Wesenberg Lund, C. (1939). Dass leben der Süsswassertiere. Wien, Springer Verlag. (p. 550-595)



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All pictures on this site were made by Gerard Visser (Almelo, Netherlands), unless stated otherwise. All rights remain with him. These pictures may not be used for purposes any other than private viewing or printing. Do NOT hardlink to these pictures or place them on other websites without the author's approval. Should you need them for purposes which include third parties, you must ask the author permission by e-mail. People, who want to use this pictures for exhibitions or publications or educative material are much encouraged to do so, after approval as mentioned and giving the normal credits.
© G.H. Visser 15-08-2006
rev. 26-05-2013

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