Ecology and life cycle of the filter-feeding Amphipsyche meridiana Ulmer 1902 (Trichoptera: Hydropsychidae) in an irrigation canal, central Thailand

The life cycle and larval diet of Amphipsyche meridiana Ulmer 1902 were investigated in a natural freshwater habitat at Kasetsart University's Kamphaeng Saen Campus in Nakhon Pathom Province, Thailand. Larvae were collected monthly from December 2021 to November 2022. Most species of Hydropsychidae have 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 0.1–0.3, 0.4–0.6, 0.7–0.9, 1.0–1.2, and 1.3–1.6 millimeters, respectively. The highest number of larvae was found in July 2022. Adult emergence occurred throughout the year, with the highest number occurring in April 2022. A. meridiana's life cycle was characterized as multivoltine, with year-round recruitment. The Canonical Correspondence Analysis (CCA) was used to determine how conditions in the environment influenced larval abundance. The factors influencing the amounts of larvae are water depth, water temperature, pH, dissolved oxygen, ammonia-nitrogen, and sulfate. The larvae of this species are omnivorous filterers. The main food types found in the gut were blue-green algae and green algae, comprising 34.11% and 33.07% of its ingestion. In addition, the digestive tract was abundant with diatoms, rotifers, and insect fragments, accounting for 32.82% of the diet.