Creeping water bugs

Definition

A family of small, oval, dorsoventrally flattened aquatic true bugs (Hemiptera: Nepomorpha: Naucoridae) that inhabit the benthic zones of streams, rivers, and ponds, where they crawl over submerged stones and vegetation to prey on small invertebrates. Unlike active swimmers such as water boatmen (Corixidae) or backswimmers (Notonectidae), naucorids lack oar-like hind legs and instead use their robust, fossorial forelegs and middle legs to cling to and move along substrates in flowing water. They breathe via air stores held against the ventral body surface and can often be recognized by their tucked, oarless hind legs and compact, shield-like appearance.

Etymology

From 'creeping' describing their substrate-crawling locomotion and 'water bugs' indicating their aquatic habitat and hemipteran affinity.

Example

In riffle habitats of Ozark streams, creeping water bugs such as Ambrysus mormon scuttle beneath cobbles to ambush chironomid larvae and small crustaceans, their flattened bodies and ventral air films allowing them to resist dislodgement by current.

Synonyms

• Naucoridae
• saucer bugs

Related Terms

• Nepomorpha
• Corixidae
• Notonectidae
• benthic macroinvertebrates
• aquatic Hemiptera
• riffle beetle
• pleustonic

Usage Notes

The common name 'creeping water bugs' refers specifically to family Naucoridae and should not be applied to other crawling aquatic bugs such as gelastocorid toad bugs or saldid shore bugs. The alternative common name 'saucer bugs' (referring to their oval, shield-like shape) is also used, particularly in older literature. Naucorids are sometimes mistaken for small belostomatid giant water bugs or for corixid nymphs, but lack the swimming hairs and elongated hind legs of Corixidae. The family is cosmopolitan but most diverse in tropical and subtropical running waters.