Caddisfly - Allomyia acanthis (Allomyia acanthis)

Category: Arthropods
Ecosystems: Riparian areas
Vulnerability to climate change (More details)


The population size and trend of Allomyia acanthis is unknown in Washington.

Caddisflies are aquatic insects. They are very sensitive to water quality and changes in water flow. Caddisflies in general are often considered an indicator of high-quality streams, suggesting that they are particularly vulnerable to changes in their habitat. 

Description and Range

Physical description

Caddisflies are closely related to the Lepidoptera (moths and butterflies). The adult’s body and wings are covered with long silky hairs (setae) – a distinctive characteristic of the order. Caddisflies are aquatic in the immature stages.

Ecology and life history

This species is normally found in very cold, high-altitude springs, seeps, and small spring streams up to six feet across. They are often found grazing on the surface or sides of larger rocks in open, sunny areas.

During the day, adults hide in cool, moist environments such as the vegetation along riverbanks. Few caddisfly adults have actually been observed feeding; they imbibe nectar.

Adults live several weeks and usually mate on vegetation or rocks surrounding water. Eggs, in masses numbering up to 800, are laid within a jelly that swells on contact with water. A female may wash off a partially extruded egg mass by dipping her abdomen into water during flight, or she may place the mass on stones in the water or on aquatic plants just above the water. Young larvae hatch within a few days and progress through multiple instars before emerging as a winged adult.

Although most larvae feed on aquatic plants, algae, diatoms, or plant debris, a few are predatory on other aquatic insects, crustaceans, and mollusks, and a few are omnivorous. The larvae play an important role in the aquatic community, reducing plant growth and disposing of animal and plant debris. 

Caddisfly adults sometimes emerge in large numbers, often forming swarms. Adults tend to remain somewhat near the emergence site where oviposition occurs. They tend to disperse shorter distances in dense forest compared with more open vegetation. Although dispersal flights are common, such flights are relatively short and only occur immediately following emergence. 

Geographic range

Adults of this species are known from the Cascade Range in Washington and Oregon. Reported from Paradise Ice Caves, Mount Rainier National Park, Pierce County, Washington. Larvae are undescribed/unknown. Allomyia species occur in very small, localized populations, with many isolated mountains inhabited by a single endemic species, and many species in this genus remain undescribed or undiscovered.

For a map of range-wide distribution and conservation status of this species, check out NatureServe Explorer.

Climate vulnerability

Sensitivity to climate change


Allomyia acanthis is an uncommon species of caddisfly found in only a few locations in the Cascade regions of Washington and Oregon. Although little is known about this species, caddisflies in the genus Allomyia are restricted to high-elevation coldwater streams in the larval and pupae stages, where they build protective cases of silk and small pieces of rock. Climate sensitivity for this species reflects their specialized habitat, which is particularly vulnerable to warming air and water temperatures, low summer flows, sedimentation from upstream erosion, and habitat fragmentation from nearby human activity (i.e., forestry practices and road construction). Caddisflies in general are often considered an indicator of high-quality streams, suggesting that they are particularly vulnerable to changes in their habitat.

Confidence: Moderate

Exposure to climate change


  • Increased air and water temperatures
  • Low summer flows
  • Increased sedimentation and erosion
Confidence: Moderate


This species is identified as a Species of Greatest Conservation Need (SGCN) under the State Wildlife Action Plan (SWAP). SGCN-classified species include both those with and without legal protection status under the Federal or State Endangered Species programs, as well as game species with low populations. The WDFW SWAP is part of a nationwide effort by all 50 states and five U.S. territories to develop conservation action plans for fish, wildlife and their natural habitats—identifying opportunities for species' recovery before they are imperiled and more limited.

Conservation Threats and Actions Needed

  • Resource information collection needs
    • Threat: Lack of data on current status and distribution
    • Action Needed: Determine distribution and population status
  • Fish and wildlife habitat loss or degradation
    • Threat: Water quality is of extreme importance to aquatic insects
    • Action Needed: Protect riparian habitats
  • Climate and severe weather
    • Threat: Drying of streams
    • Action Needed: Determine distribution and population status

See the Climate vulnerability section for more information about the threats posed by climate change to this species.



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Clemson University Department of Entomology (J.C. Morse, ed.). 2002. Last Updated 5 September 2006. Trichoptera World Checklist. Online. Available:

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NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available

Ruiter, D. E., B. C. Kondratieff, R. A. Lechleitner, and R. E. Zuellig. 2005. An annotated list of the caddisflies (Trichoptera) of Mt. Rainier National Park, Washington, USA. Transactions of the American Entomological Society 131(1/2): 159-187.

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B. Kondratieff, Colorado State University, pers.comm.

D. Ruiter, University of Texas, pers.comm.

Other resources