Wonder caddisflies are winged, moth-like insects with long antennae and with aquatic larvae that construct portable casings and emerge from the water when mature. At less than 0.39 in. (1 cm), the wonder caddisfly is a remarkably small caddisfly. Adults have uniformly colored medium brown forewings about 5 mm long, with the body and appendages light brown in color. Standard species level identification for members of this genus currently requires microscopic examination of the adult male or female genitalia.
The wonder caddisfly has been found only in small, cold, high gradient, montane streams along relatively moist, cool upland slopes below timberline dominated by large coniferous trees. These perennial streams must maintain consistent flow and be situated near springs, seeps, and low-intensity waterfalls, and they must also include talus slopes (naturally occurring jumbles of loose, fallen rocks) that form below waterfalls. Cool-cold year-round stream temperatures are required to support Neothremma populations. Larvae live on rocks or wood that is consistently wetted by splashing water and mist from waterfalls or by the thin streams or springs of water running on the surfaces of the talus slope. Pupae are most often found in rock aggregations at the base of falls or beneath rocks in the talus slope zone.
Limiting factors
The wonder caddisfly is highly vulnerable to any change to its habitat due to its extremely small population size and narrow, isolated habitat. The caddisfly is particularly sensitive to changes in water temperature, velocity, dissolved-oxygen levels, and substrate characteristics in its stream habitat. Larvae and pupae of this species are highly sensitive to disturbance of the mineral substrate which they inhabit, as well as to increased inputs of fine sediment, increased water temperatures caused by removal of the forest canopy, and shifts in algal community composition. Occupied sites are heavily impacted from human activity, both recreational activities and transportation and service corridors. Populations could be adversely impacted by forest management activities that involve trail maintenance and harvesting of timber in the watershed. Loss of habitat due to drought and altered fire regimes are emerging threats.
Data gaps
Collect life history information. Obtain current population size and trend data. Determine microhabitat requirements. Use DNA barcoding to determine species distribution and range.
Conservation actions
Protect known occurrences from disturbances that could adversely affect any life stage. Survey suitable habitat for new populations. Minimize fine sediments entering occupied streams during maintenance or management activities.
Key reference or plan
Townsend, M. E.. 2024. Petition to list the Wonder Caddisfly (Neothremma prolata) as an Endangered Species. The Center for Biological Diversity. 20 pp.
Fallon, C. 2017. Species Fact Sheet for Neothremma prolata. Prepared for USDA Forest Service Region 6 and USDI Bureau of Land Management, Oregon and Washington Interagency Special Status and Sensitive Species Program.
