Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Clickable Guide
Moths Butterflies Flies Caterpillars Flies Dragonflies Flies Mantids Cockroaches Bees and Wasps Walkingsticks Earwigs Ants Termites Hoppers and Kin Hoppers and Kin Beetles True Bugs Fleas Grasshoppers and Kin Ticks Spiders Scorpions Centipedes Millipedes

Upcoming Events

National Moth Week photos of insects and people. Here's how to add your images.

Photos of insects and people from the 2019 BugGuide Gathering in Louisiana, July 25-27

Discussion, insects and people from the 2018 gathering in Virginia, July 27-29

Photos of insects and people from the 2015 gathering in Wisconsin, July 10-12

Photos of insects and people from the 2014 gathering in Virginia, June 4-7.

Photos of insects and people from the 2013 gathering in Arizona, July 25-28

Photos of insects and people from the 2012 gathering in Alabama

Photos of insects and people from the 2011 gathering in Iowa

Current number of accepted arachnid orders


I am working on an arachnid outreach lecture for our local Audubon Center and I am running into some problems regarding the current number of extent arachnid orders. I was under the impression it was 11 and then I saw the work that has been done within Acari and now I am really stumped. What's more, BG says 12 arachnid order but then lists 17 (with four orders under Acariformes. I thought there were only two?)! Can anyone help clarify? This is for the general public who probably don't need/want to know about the madness that is the mites.

Marian L. Kirst

Wikipedia ...
lists 12. Horseshoe crabs (Xiphosura) were a recent addition in 2019.

Wow, I don't know how I missed that last year. I have a google alert set up for arachnid news and everything!

I'm still confused, though, by BugGuide's arachnid taxonomy. Am I right in thinking that, if you consider all the different orders within Subclass Acari, BugGuide lists 17 arachnid orders in total? And that is not including the horseshoe crabs.

I’m not sure.
It looks like the Acari numbers aren’t settled so it gets glossed over.. My focus is just spiders but I had heard about the horseshoe crabs. I was thinking the 11 a lot of sources cite plus the recent addition of horseshoe crabs makes 12. Just to confuse things more ... comparing the Wikipedia list against BugGuide’s I see that Thelyphonida = Uropygi & Schizomida. BugGuide lists Uropygi and Schizomida, Wikipedia lists Thelyphonida and Schizomida.

Comment viewing options
Select your preferred way to display the comments and click 'Save settings' to activate your changes.