Japanese Dobsonfly vs Large Alderfly

Side-by-side species comparison

Attribute Japanese Dobsonfly Large Alderfly
Scientific Name Protohermes grandis Sialis nigripes
Order Megaloptera Megaloptera
Family Corydalidae Sialidae
Size 40-60 mm body length 15-20 mm
Habitat Rivers & Streams Rivers & Streams
Diet Predators Herbivores
Regions East Asia, Japan North America
Conservation Least Concern Least Concern

Japanese Dobsonfly

A large aquatic insect known as 'hebi-tonbo' (snake dragonfly) in Japanese. The adult males have elongated, curved mandibles. Larvae called 'magotaro-mushi' are used as fishing bait.

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Did You Know?

Dobsonfly larvae are prized as live fishing bait in Japan and are collected from stream rocks by anglers targeting ayu (sweetfish).

Large Alderfly

A relatively large alderfly with dark wings and black legs found near rivers in eastern North America. Adults rest on streamside vegetation during the day.

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Did You Know?

Alderfly larvae breathe through feathery gills along their abdomen and a single long tail filament that acts as an additional gill.