Thursday, 3 August 2006

Army Ant Mites: the Most Specialized Mites Found on Any Social Insect

R. J. Elzinga, Dept. of Entomology, Kansas State University, Manhattan, KS, C. W. Rittenmeyer, Dept. Ecology & Evol. Biology, University of Connecticut,, Storrs, CT, and Stefanie M. Berghoff, School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, United Kingdom.

It is difficult for other animals to infiltrate and keep up with ferocious and migratory army ant colonies. Nevertheless, hundreds of arthropods are associated with these ants, and mites are the most abundant and diverse group.  Examination of samples of army ants (Ecitoninae) from 1,600 colonies has yielded over 45,000 mites.  About 3% have been studied resulting in the description of 3 new families and 149 new species.  Only one described mite species was found.  The mites have evolved many strategies to stay with their colonies.  Four species of Larvamima (Larvamimidae) mimic the ant larvae and are carried during emigrations.  The new family Pynoglyphidae has only been seen attached to a worker eye.  Mites in 1-4 disputed families of Uropodina  are restricted to a single species or several related ants.  They are further restricted to being ectoparasitic or phoretic on a specific part of an ant or even a specific surface on that part. All 14 species of Planodiscus probably ride on the underside of the middle or hind tarsi of workers.  Circocylliba crinita is not only restricted to the mandibles of soldiers of Eciton dulcium but has only been found riding on the inner curve of the mandibles.  Other Uropodina are highly modified to clamp around the coxae or the antennal scapes of workers.  The Ascidae are ectoparasites feeding at the base of the mandibles of the workers.  Macrocheles has two species that insert their mouthparts between the tarsal claws of the hind legs of large workers. Only 5 localities have been well sampled from the Southern US to Argentina.  Therefore, there must be thousands of undiscovered mite species with Ecitoninae. The extreme morphological specialization is thought to be a result of the fact that army ant colonies have been immortal for 100 million years.

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