On the common alderfly: adults live only two to three days.

“They are bad fliers and never leave the waters where the larvae have developed. Females lay a large quantity of eggs on plants overhanging the waters, where larvae will fall after hatching. Larvae are aquatic predators of small invertebrates and usually wait for their prey in silt or under stones just emerging from the water. The life cycle in this species lasts about one-two years, but the adults live two-three days only, without feeding.”

https://en.m.wikipedia.org/wiki/Sialis_lutaria

#Megaloptera #entomology