The larva of Macrostemum indistinctum Banks 1911 (Trichoptera: Hydropsychidae): description, life cycle, and notes on biology

Information from the abstract

There have been limited systematic studies on Trichoptera larvae in Thailand. The larval stages of the endemic species remain mostly unknown. The description of the larvae, life cycle, and diet of Macrostemum indistinctum Banks, 1911, was studied in the stream flow and outlet of Kasiow Dam, located in Suphan Buri Province, central Thailand. Larvae were collected monthly from January to December 2025. A total of 1929 larvae were sampled and had the head capsule width measured. M. indistinctum has five larval instars. The first to fifth larval instars were found in the stream throughout the year. Head capsule widths of the first to fifth instar larvae were 0.13–0.18, 0.26–0.44, 0.50–0.81, 0.83–1.36, and 1.38–1.98 millimeters, respectively. M. indistinctum's life cycle was characterized as multivoltine, with year-round recruitment. The unknown larvae of M. indistinctum were matched with their identities deduced from the fact that the larvae described here and identifiable adult specimens were sampled at the same location. The Canonical Correspondence Analysis (CCA) was used to determine how conditions in the environment associated with larval abundance. The factors influencing the amounts of larvae are water temperature, turbidity, total dissolved solids, electrical conductivity, pH, dissolved oxygen, ammonia-nitrogen, nitrate-nitrogen, and orthophosphate. The larvae of this species are omnivorous filterers. The main food types found in the gut were diatoms, green algae, blue-green algae, gastropods, arthropods, rotifers, and protozoa. M. indistinctum was found to be an omnivorous collector organism.

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Related topics: Freshwater macroinvertebrate diversity and ecology · Invertebrate Taxonomy and Ecology · Fish Biology and Ecology Studies