Summer diapause in soil by the terrestrial larvae of the caddisfly Nothopsyche montivaga (Nozaki, 1999) (Trichoptera: Limnephilidae)

Nothopsyche montivaga (Nozaki, Citation1999) is one of the few completely terrestrial caddisflies. Larvae develop only in the terrestrial environment during spring before entering diapause in early summer while adults emerge in late autumn. In this study, 513 larval cases were found in soil during field collections. Larvae were found in 82 of those cases. Their behaviour of moving into soil to pass the summer resembles that of other caddisfly larvae that live in terrestrial habitats during their larval development. Nothopsyche montivaga larvae move into soil having a certain moisture content as an adaptation to dry summer conditions. In the field, larvae sealed the entrances of cases as late as early October, indicating diapause was terminated. Adults then emerged in November. In the laboratory, larvae were reared under either a long-day or short-day photoperiod at a constant temperature of 20 °C. The median dates of case sealing under the short- and long-day conditions were 23 October and 8 November, respectively. Therefore, from the field observations and rearing experiments in the laboratory, it is considered that the larval summer diapause plays a significant role in the adult emergence in late autumn in completely terrestrial N. montivaga.