Under Construction


Holothyrans, ticks and mesostigmatic mites

David Evans Walter
Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window
taxon links [up-->]Ixodida [down<--]Acari Interpreting the tree
close box

This tree diagram shows the relationships between several groups of organisms.

The root of the current tree connects the organisms featured in this tree to their containing group and the rest of the Tree of Life. The basal branching point in the tree represents the ancestor of the other groups in the tree. This ancestor diversified over time into several descendent subgroups, which are represented as internal nodes and terminal taxa to the right.

example of a tree diagram

You can click on the root to travel down the Tree of Life all the way to the root of all Life, and you can click on the names of descendent subgroups to travel up the Tree of Life all the way to individual species.

For more information on ToL tree formatting, please see Interpreting the Tree or Classification. To learn more about phylogenetic trees, please visit our Phylogenetic Biology pages.

close box
Hypotheis by Lehtinen (1991)
Containing group: Acari


The Parasitiformes is one of the three major lineages of chelicerate arthropods that are called mites. Ticks are among the most economically important parasitiform mites, but numerous Mesostigmata, especially in the Dermanyssoidea are also debilitating parasites of mammals, birds, and reptiles. The phytoseiid mites used in biological control belong to the Mesostigmata, as do numerous species of predators that inhabit soil-litter systems. Currently, both the Ixodida (ticks) and Holothyrida consist of three families; the Mesostigmata contains approximately 70 family-level taxa.


Parasitiform mites have free coxae, a ventral anal opening covered by a pair of plates, corniculli on the hypostome (lost in ticks), a sclerotised ring surrounding the gnathosoma (capitulum), and usually a biflagellate tritosternum (lost in ticks, many holothyrids, and some parasitic Mesostigmata).

Discussion of Phylogenetic Relationships

The hypothesis by Lehtinen (1991) supports a sistergroup relationship between Holothyrida and Ixodida; however, other acarologists have suggested that ticks and Mesostigmata are sistergroups. Phylogenetic analyses addressing the proper placement of ticks are underway in Queensland and Ohio.

Other Names for Parasitiformes


Lehtinen, P.T. 1991. Phylogeny and zoogeography of the Holothyrida. In: Dusabek, F. and Bukva, V. (eds.) Modern Acarology, Volume 2. SPB Academic Publishers, The Hague, pp. 101-113.

Title Illustrations
Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

SEM of Allothyrus sp. from Queensland (D.E. Walter)

Scientific Name Allothyrus sp.
Location Queensland
Image Use creative commons This media file is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0.
Copyright © 1996
About This Page

University of Alberta, Edmonton, Alberta, Canada

Correspondence regarding this page should be directed to David Evans Walter at

Page: Tree of Life Parasitiformes. Holothyrans, ticks and mesostigmatic mites. Authored by David Evans Walter. The TEXT of this page is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

Citing this page:

Walter, David Evans. 1996. Parasitiformes. Holothyrans, ticks and mesostigmatic mites. Version 13 December 1996 (under construction). http://tolweb.org/Parasitiformes/2566/1996.12.13 in The Tree of Life Web Project, http://tolweb.org/

edit this page
close box

This page is a Tree of Life Branch Page.

Each ToL branch page provides a synopsis of the characteristics of a group of organisms representing a branch of the Tree of Life. The major distinction between a branch and a leaf of the Tree of Life is that each branch can be further subdivided into descendent branches, that is, subgroups representing distinct genetic lineages.

For a more detailed explanation of the different ToL page types, have a look at the Structure of the Tree of Life page.

close box


Page Content

articles & notes



Explore Other Groups

random page

  go to the Tree of Life home page