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Acari

What do they look like?

This is a very big group of very diverse and very small species of arachnids. The biggest are the ticks, some of them can be over 2.5 cm long. They are giants compared to most mites. Ticks are actually just one group of mites, so we will use "mites" to refer to mites and ticks both. Most mites are less than 1 mm long, and some other mites are the smallest arachnids, they grow to less than 0.2 mm.

Like all arachnids, most mites have eight legs (but see "How Do They Grow"). On the front of the body they have two sets of mouthparts. The outside set are called palps, and they are similar to the pedipalps in spiders, They look like tiny short legs, and are used for sensing things and grabbing prey. Between the palps are the mouthparts, called "chelicerae" (kel-iss-er-ee). Different groups of mites have different kinds of mouthparts: some are sharp tubes for stabbing and sucking, some are pincers for grabbing and cutting, some are like combs for filtering little particles of food.

Some mites have eyes, but many are blind. They all have bristles and hairs on their bodies that they use to sense their environment.

Unlike spiders and most other arachnids, the bodies of mites and ticks are not divided into sections. The only other group of arachnids with bodies like this are the harvestmen, but they are much larger and have much longer legs.

Most mites are brown, but some groups are partly red or yellow, and some water mites are blue, green, or even purple.

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    0.2 to 25.0 mm
    0.01 to 0.98 in

Where do they live?

Mites are everywhere. Mites live on every continent (including Antarctica!) and in every ocean. Scientists know less about mites than about most other animals; they don't even have a very good guess how many species of mites there are. So far there are 40,000 species of mites known to science, and there are probably 500,000 to a million more species in the world, still unknown.

What kind of habitat do they need?

The ancestors of mites lived in soil and dead leaves, and that's where the most diversity of mites is, but mites have evolved and adapted to almost every habitat on Earth. They live everywhere on land: from hot deserts to cold caves, from rainforest to arctic tundra. They are found in every kind of freshwater.

In the ocean they are all over the bottom, on coral reefs, mud flats, and in deep trenches. About the only place they don't live in the ocean is swimming in open water.

Many mite species are parasites, and live on or inside other organisms.

How do they grow?

Mites hatch from eggs. As they grow, they have to shed their exoskeleton all at once, this is called molting. Many mites go through metamorphosis, in which their body changes as they grow. The first active stage of a mite is called a larva, it has six legs. After its first molt, it is called a protonymph and has eight legs. It molts (and sometimes changes body shape) two more times before it becomes an adult. Not all mites do this, some species skip some stages. Other species change a lot between stages, starting out as small parasites but later becoming big fuzzy predators. Other mites have a stage that is specialized for traveling. It has big claws to grab on to a larger animal (like a beetle or an ant) and catch a ride to a new food source.

How do they reproduce?

After mating, most female mites lay eggs. In some species they keep the eggs inside until the young are ready to hatch. A single female mite can lay from dozens to hundreds of eggs.

Some species of mites reproduce without mating. Each member of these species is a female, and can lay eggs that grow and hatch without being fertilized.

In most mite species, the only parental care is when the female chooses a place to lay her eggs. Males don't help at all, and the female leaves after laying. In a few species, the mother guards her eggs, or holds them in her body for protection until they hatch.

How long do they live?

Most mites live a year or less. Some short-lived species go from egg to adult in a couple of weeks, and usually only live a few weeks. Some slow-living soil species can live for several years.

How do they behave?

Different mites species are active at all times of day and night. Most are solitary, only coming together to mate, but some plant mites live together in groups under their webbing. Most mites don't make homes, but just move around looking for food, and hiding where they can.

How do they communicate with each other?

Mites mainly communicate by touch and scent, and by taste when they are close to each other. Males and females mainly use scent to find each other when they are looking for mates.

Mites have very poor eyesight when they can see at all. The best most can do is tell light from dark.

What do they eat?

Mites eat many different kinds of foods. Some species suck juice from plants, some eat fungi, some eat other small animals. Some are filter-feeders, feeding on protists and other cells growing in liquid. A few species are parasites, feeding on the bodies or blood of larger animals. Every group of animal has mite parasites except fish.

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
    • eats eggs
    • eats non-insect arthropods
  • herbivore

What eats them and how do they avoid being eaten?

Most mites hide when they can. Some species have very hard exoskeletons to protect them. Others have toxic chemicals in their bodies so they taste bad. These toxic mites are often brightly-colored to warn their predators not to bother. Some plant mites spin webs and hide under them. The webs tangle and slow down small predators.

What roles do they have in the ecosystem?

Many soil mites help break down dead plant material and improve the soil. Some parasitic mites carry diseases that have strong effects on their hosts. Many mite species live in the nests of other animals.

Species (or larger taxonomic groups) used as hosts by this species
  • Different mites species are parasites of every kind of animal except fish.
Species (or larger taxonomic groups) that are mutualists with this species
  • Social insects (ants, termites, wasps, bees)
Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • Social insects (ants, termites, wasps, bees)
  • Bird nests
  • Mammal nests

Do they cause problems?

Some mite species are obnoxious parasites of people and animals, and some carry diseases that they give to their host when they bite. Some plant mites are major pests of farmer's crops, and a few species of mites are pests in stored food.

How do they interact with us?

Some mite predators are important for controlling pests in agriculture (they eat plant mites and larvae of pest insects). A few herbivorous mites have been used to control weeds.

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

No mite species are known to be endangered, but we don't know very much about most of them, and very few people pay much attention to them. Some mite species live on larger species that are endangered, and if the larger host species is endangered, then the mites species probably is too.

  • IUCN Red List [Link]
    Not Evaluated

Contributors

George Hammond (author), Animal Diversity Web.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Hammond, G. . "" (On-line), Animal Diversity Web. Accessed December 10, 2017 at http://www.biokids.umich.edu/accounts//

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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