I did a bit more searching on my own question and eventually turned up this page on water mites (Hydracarina) from the the Tree of Life: http://tinyurl.com/bmkef.
>From the Life History section:
"One of the most striking things about water mites is their often brilliant colouration. Scarlet, orange, red and yellow mites are common, and are extremely visible against a background of green water plants. These bright mites are often very unpalatable to fish (Kerfoot 1982), presumably due to noxious secretions from their skin glands. Although one might expect this aposematic connection between redness and distastefulness to have evolved as an anti-fish-predation mechanism, both the bright colour and foul taste are also present in terrestrial parasitengones (Garga 1996)."
-Jase
> Date: Mon, 08 Aug 2005 15:40:31 -0500
> From: dlmcneely-in-lunet.edu
> Subject: Re: NANFA-L-- Red water mites -- poisonous?
>
> Don't know if these things are toxic. They are not parasites, but
> rather are predaceous on other small inverts. You are right that the
> bright red, highly visible color suggests a warning as in bees,
> butterflies, reptiles, whether toxic or venomous. But other mites are
> bright red too; to whom might chiggers be putting out a warning?
> Certainly not us or their normal hosts of lizards and birds.
>
> David L. McNeely, Ph.D., Professor of Biology
> Langston University; P.O. Box 1500
> Langston, OK 73050; email: dlmcneely-in-lunet.edu
> telephone: (405) 466-6025; fax: 405) 466-3307
> home page http://www.lunet.edu/mcneely/index.htm
/-----------------------------------------------------------------------
/ This is the discussion list of the North American Native Fishes
/ Association (NANFA). Comments made on this list do not necessarily
/ reflect the beliefs or goals of NANFA. For more information about NANFA,
/ visit http://www.nanfa.org Please make sure all posts to nanfa-l are
/ consistent with the guidelines as per
/ http://www.nanfa.org/guidelines.shtml To subscribe, unsubscribe, or get
/ help, visit the NANFA email list home page and archive at
/ http://www.nanfa.org/email.shtml