Ectemnius continuus

Distinguished from similar Ectemnius species by the 12 antennal segments in both sexes (most aculeate males have 13). Male specimens can be identified by the small spines on the first and second tarsomeres of the mid tarsus. The combination of yellow-marked black coloration with silver-haired clypeus helps separate it from related genera such as Anacrabro, Lestica, and Crabro; unlike Anacrabro, Ectemnius has a convex rather than concave underside of the abdomen.

Black body with yellow markings on the scapes (antennal bases), pronotum (thoracic segment behind head), tibiae (lower leg segments), and tergites (abdominal segments). Clypeus (lower part of face) covered with dense, shining silver hairs. Both sexes possess 12 antennal segments. Males have distinctive small spines on the first and second tarsomeres of the mid tarsus. Size is small to medium for the genus.

Woodlands, gardens, and farmland. Nests are constructed in cavities in dead wood, particularly old beetle burrows in tree stumps and standing dead wood.

Widespread throughout the Holarctic region. Found in Africa, Europe and Northern Asia (excluding China), North America, and Southern Asia. In the United Kingdom, common particularly across the south.

Flight period from early May to late September. Likely bivoltine (two generations per year) in the southern UK; univoltine (single generation) elsewhere.

Adults visit flowers of umbellifers for nectar. Females hunt medium-sized Diptera (true flies) including Syrphidae (hoverflies), Muscidae (house flies and relatives), and Calliphoridae (blow flies). Tabanidae (horse flies) and Therevidae (stiletto flies) have also been recorded as prey.

Univoltine to bivoltine depending on latitude. Nests contain up to 10 cells, with each cell provisioned with 6-8 flies. Nest structure varies from straight to branching. One larva develops per cell, feeding on the stored prey.

Females hunt flies to provision nest cells. Adults are strongly associated with umbellifer flowers including angelica, hogweed, wild carrot, wild parsnip, fennel, cow parsley, and water-dropwort, visiting for both nectar and to hunt prey. Nest entrances are in pre-existing cavities in dead wood rather than excavated in soil.

Predator of medium-sized Diptera; contributes to regulation of fly populations. Pollinator of umbellifer flowers through nectar feeding.

Potential biocontrol agent for pest fly populations. Non-aggressive; does not defend nests aggressively. Presence in gardens and farmland indicates healthy dead wood habitat.

• Anacrabro ocellatusSimilar black-and-yellow coloration and size, but Anacrabro has a very concave underside of the abdomen (Ectemnius has convex), nests in soil rather than wood, and hunts Miridae plant bugs rather than Diptera flies.
• Other Ectemnius speciesMost similar species have males with 13 antennal segments; E. continuus males have only 12 segments and distinctive spines on mid tarsus tarsomeres 1-2.
• Lestica and CrabroRelated genera in tribe Crabronini with similar general appearance; distinguished by specific combinations of facial sculpture, clypeal hair patterns, and male genitalia.

• digger wasp
• square-headed wasp
• Holarctic
• wood-nesting
• fly predator
• umbellifer visitor

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Wasp Wednesday: Anacrabro ocellatus
• The genome sequence of a digger wasp, Ectemnius continuus (Fabricius, 1804).