Not much love is lost on the mites and ticks of this world. Most people know little about them, other than the fact that some transmit diseases. The order name, Acari, derives from the Greek word Akari, meaning a small thing. They may be small, but mites and ticks have a big impact on our world.
Many mites and ticks are ectoparasites of other organisms, while some prey on other arthropods. Still, others feed on plants or decomposed organic matter like leaf litter. There are even gall-making mites. Take just a scoop of forest soil and examine it under a microscope, and you may find several hundred species of mites. Some are vectors of bacteria or other disease-causing organisms, making them a significant public health concern. Members of the order Acari are diverse, abundant, and sometimes economically important, though we know relatively little about them.
Most mites and ticks have oval-shaped bodies, with two body regions (prosoma and opisthosoma) that may appear fused together. The Acari are indeed small, many measuring a mere millimeter long, even as adults. Ticks and mites go through four life cycle stages: egg, larva, nymph, and adult. Like all arachnids, they have 8 legs at maturity, but in the larval stage, most have just 6 legs. These tiny organisms often disperse by hitching rides on other, more mobile animals, a behavior known as phoresy.
Habitat and Distribution
Mites and ticks live just about everywhere on Earth, in both terrestrial and aquatic habitats. They live virtually everywhere that other animals live, including in nests and burrows, and are abundant in soil and leaf litter. Though over 48,000 species of mites and ticks have been described, the actual number of species in the order Acari may be many times that. Well over 5,000 species inhabit the U.S. and Canada alone.
Groups and Suborders
The order Acari is somewhat unusual, in that it is subdivided first into groups, and then again into suborders.
Group Opilioacariformes - These mites look somewhat like small harvestmen in form, with long legs and leathery bodies. They live under debris or rocks and may be predaceous or omnivorous feeders.
Group Parasitiformes - These are medium to large mites that lack abdominal segmentation. They breathe by virtue of paired ventrolateral spiracles. Most members of this group are parasitic.
- Suborders of the Parasitiformes:
- Suborder Holothryina
- Suborder Mesostigmata
- Suborder Ixodida - Ticks
Group Acariformes - These small mites also lack abdominal segmentation. When spiracles are present, they're located near the mouthparts.
- Suborders of the Acariformes:
- Suborder Prostigmata
- Suborder Astigmata
- Suborder Oribatida
- Borror and DeLong's Introduction to the Study of Insects, 7th edition, by Charles A. Triplehorn and Norman F. Johnson.
- NWF Field Guide to Insects and Spiders of North America, by Arthur V. Evans
- Latin American Insects and Entomology, by Charles Leonard Hogue
- Introduction to the Acari, University of California Museum of Paleontology. Accessed February 26, 2013.
- Arachnida: Acari, class handouts from University of Minnesota Entomology Department. Accessed online February 26, 2013.
- Soil Arthropods, National Resources Conservation Service. Accessed February 26, 2013.