Arctopsyche grandis

(Banks, 1900)

netspinning caddisfly

Arctopsyche grandis is a of netspinning caddisfly in the Hydropsychidae, found in North America. Larvae construct silk nets to capture food in flowing water and complete their development in approximately one year. The species has been studied in Central Idaho streams where it reaches high densities on rocky substrates.

Common netspinner, Arctopsyche grandis (9653649731) by Bob Henricks from Charlottesville, United States. Used under a CC BY-SA 2.0 license.

Common netspinner, Macrostemum sp. (29622807021) by Bob Henricks from Charlottesville, United States. Used under a CC BY-SA 2.0 license.

Common netspinner, Arctopsyche grandis (7882480424) by Bob Henricks from Charlottesville, United States. Used under a CC BY-SA 2.0 license.

Pronunciation

How to pronounce Arctopsyche grandis: //ˌɑrktoʊˈsaɪki ˈɡrændɪs//

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Identification

Larvae can be distinguished from other hydropsychid by their net-spinning and association with lotic . Net dimensions correlate with capsule width, allowing instar determination. require identification; the is part of the diverse Hydropsychidae where morphological separation of similar species often depends on genitalic characters.

Images

Appearance

are medium-sized with wings typically held roof-like over the body. Larvae possess a hardened capsule with head capsule widths ranging from 403–2197 μm across instars. Body weight increases from approximately 0.05 mg to 16.23 mg AFDW (ash-free dry weight) from first to fifth instar. Larvae produce silk nets for food capture.

Habitat

Cold, flowing streams with rocky substrates. Larvae attach to planar rock surfaces where they construct capture nets. The occupies lotic freshwater in montane or temperate regions.

Distribution

North America; confirmed present in Central Idaho streams. GBIF records indicate presence across the Nearctic region.

Seasonality

Larvae present year-round with multiple instars coexisting in most months. timing not specified in available sources.

Diet

Larvae feed preferentially on animal prey and diatoms, actively avoiding vascular plant detritus. No dietary differences detected among instars.

Life Cycle

(one-year ) with five larval instars. Three to four instars are typically present simultaneously in most months. Rapid growth occurs during summer, with first and second instars progressing to fourth and fifth instar within 30 days or less. Growth ceases or is minimal during winter months. survival follows a negative exponential curve.

Behavior

Larvae construct and maintain silk capture nets throughout the year. Nets are actively maintained and their dimensions with larval size. Larval can reach high densities (up to 2060 individuals per square meter of rock surface).

Ecological Role

Larval silk nets modify local hydrodynamics and capture organic matter, influencing nutrient cycling in stream . As and grazers on diatoms and animal prey, larvae occupy an intermediate trophic position. High densities suggest substantial contribution to secondary production in suitable .

Similar Taxa

Other Hydropsychidae speciesMany hydropsychid share net-spinning larval and rocky stream ; identification to typically requires examination of genitalia or detailed larval

More Details

Population dynamics

Maximum larval densities of 547 m⁻² (1977) and 2060 m⁻² (1978) recorded on planar rock surface area in Central Idaho study. followed negative exponential curves with exponents of −0.0078 and −0.0103 in consecutive years.

Growth patterns

Larval growth is generally isometric, with capsule width and weight increasing by a factor of approximately 1.5 between successive instars.