Terrestrial feeding migration and life history of the stream-dwelling caddisfly, Desmona bethula (Trichoptera: Limnephilidae)

Abstract

A caddisfly larva, D. bethula (Trichoptera: Limnephilidae), lives in slow, unshaded stretches of small spring streams at the Sagehen Creek Field Station in the Sierra Nevada, California, USA. On early summer nights, while in the 5th instar, it leaves the water and feeds on several species of semiaquatic plants. It returns to the water when air temperatures approach freezing and on warm, still nights stays out until dawn. Three factors (light intensity, vapor pressure deficit and temperature) determine when diel migration begins and how long it lasts. Mark-recapture estimates indicated that 14-16% of the population migrated on 2 nights during the primary feeding period. Population estimates were 1220 and 1662/m2. D. bethula is a univoltine autumn-emerging caddisfly. It may represent an evolutionary link between the few secondarily terrestrial Linnephilidae larvae and the majority of aquatic caddisfly larvae.