Overview

After the insects, mites (Acari
Factsheet for:Acari
Glossary:Opilioacariformes:
an obsolescent supraordinal term used for the Opilioacarida.
or Acarina) are the most diverse and challenging group of arthropods encountered in quarantine. There are more than 50,000 described species, though estimates suggest that the actual species richness may be over one million.

Like insects, but unlike their arachnid relatives (spiders, scorpions and the like), the feeding ecologies of mites go well beyond predation to include herbivory and parasitism. The Acari
Factsheet for:Acari
Glossary:Opilioacariformes:
an obsolescent supraordinal term used for the Opilioacarida.
includes a host of plant parasites that can devastate crops by their feeding, forming galls and various deformities or by transmitting plant pathogens. Domestic and wild animals also are infested by a bewildering diversity of parasitic mites, including those that cause debilitating disease. House dust mites cause allergies affecting nearly 30% of the world populations. Even other arthropods are not immune, as the worldwide spread of the honeybee parasite Varroa destructor has demonstrated. For plant-feeding mites, invasions followed by an outbreak in a new area may have a significant impact on agriculture. As an example, the lychee mite (Aceria litchii) has reduced yields by 70% to 80% and increased production costs by 20%.

Because mites are tiny (mostly less than 1 mm in length as adults and many less than 0.25 mm); highly diverse; omnipresent in crops, soil, timber, warehouses and other human habitations, and on animals, they present a major challenge to quarantine. This is especially true since there are very few people who have studied mites broadly and who can give taxonomic support to quarantine officers. Even innocuous mites (which will always be the vast majority of mite intercepts) can be difficult to identify with a level of certainty that will allow for prompt regulatory decisions. This tool will help to alleviate this situation by providing a comprehensive mite identification resource that is easy to understand by a layperson.

The motivation for this tool is to prevent potentially dangerous agriculturally important plant-feeding mites from being introduced into new areas, particularly the U.S. Invasive Mite ID is designed to provide support to quarantine workers at three levels: (1) to allow a USDA quarantine officer to quickly sort a mite intercept into a group (non-actionable vs. potentially actionable) for further identification; (2) training in acarine morphology and identification through use of the tool’s content; and (3) advanced taxonomic support.

The keys and fact sheets for each mite group covered range in complexity from Is it a mite?, at a very basic introductory level, to species level treatments (e.g., Stratiolaelaps). The mite groups covered are interrelated, each treating taxa at various taxonomic levels. There is also an extensive, illustrated glossary with 780 terms (including about 150 morphological terms) defined.

In 2025, USDA-APHIS-PPQ-S&T, Pest Identification Technology Lab (PITL), Identification Technology Program (ITP) migrated the tool's content from a static site last updated in 2006 to ITP's Fact Sheet Manager 3, a content-management system. Classification above genera was updated, see "About Mite Classification" page. Taxonomic training videos were added in 2025. Any updates to content are noted. Links were modified for functionality.

We hope Invasive Mite ID will prove successful in supporting quarantine activities and welcome any suggestions for the tool's improvement or any corrections needed (itp@usda.gov).

About this tool