Trout-Stream Beetles

Pronunciation

How to pronounce Amphizoidae: /ˌæmfɪˈzoʊɪdaɪ/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Images

Summary

Amphizoidae, or trout-stream beetles, are a distinct family of aquatic beetles characterized by their oval shape, predatory diet, and specific habitat preferences in cold flowing streams. They are not well adapted for swimming despite being aquatic.

Physical Characteristics

Troutstream beetles are relatively large and oval, with a slightly convex shape. They have a dull black to piceus coloration, body length ranging from 11–16 mm (0.43–0.63 in). The head is broad and quadrate with small round eyes. The antennae are filiform, short, and consist of 11 segments. The pronotum is narrower than the elytra, which are vaguely striate and have a series of short spines. Legs are not well adapted for swimming and lack long swimming setae.

Identification Tips

Look for their characteristic oval shape, dull coloration, and the broad quadrate head with small eyes. The short antennae and the elytra with short spines are also characteristic features.

Habitat

Found in streams and rivers in mountain regions, particularly in cold, medium to fast flowing water.

Distribution

Three known species in western North America and two in the eastern Palearctic (China, North Korea).

Diet

Both adults and larvae are predators, primarily on stonefly larvae and occasionally on other aquatic insects. Larvae may also scavenge dead insects.

Life Cycle

Life cycle specifics are not detailed, but includes both adult and larval stages with predatory behaviors.

Predators

Predators of troutstream beetles include frogs and toads, which may be deterred by the beetles' defense mechanism that involves exuding a yellowish fluid with a strong odor.

Ecosystem Role

Predators in their aquatic habitat, contributing to the regulation of aquatic insect populations.

Evolution

Amphizoidae share plesiomorphic features with Carabidae but also share characteristics with Dytiscidae. Their phylogenetic placement suggests they are closely related to Aspidytidae and Dysticidae.

Similar Taxa

• Carabidae
• Dytiscidae
• Aspidytidae

Tags

• Amphizoidae
• trout-stream beetles
• aquatic beetles
• Coleoptera
• predatory insects