Crabro

Fabricius, 1775

Shield-handed Wasps, Square-headed Wasps

Crabro is a of solitary in the Crabronidae, commonly known as shield-handed or square-headed wasps. The genus contains at least 80 described distributed across the Nearctic and Palaearctic regions (Holarctic). These wasps nest in sandy soils, constructing multi-celled burrows provisioned with () for their .

Crabro vernalis by (c) Alexandria 'Alex' Wenninger, some rights reserved (CC BY), uploaded by Alexandria 'Alex' Wenninger. Used under a CC-BY license.Crabro vernalis by (c) Alexandria 'Alex' Wenninger, some rights reserved (CC BY), uploaded by Alexandria 'Alex' Wenninger. Used under a CC-BY license.Crabro vernalis by (c) Alexandria 'Alex' Wenninger, some rights reserved (CC BY), uploaded by Alexandria 'Alex' Wenninger. Used under a CC-BY license.

Pronunciation

How to pronounce Crabro: /ˈkra.broʊ/

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Identification

Members of Crabro can be distinguished from similar in the tribe Crabronini by the shape of the : the underside is very concave, unlike the flatter surface seen in Ectemnius, Lestica, and Anacrabro. The "square-headed " refers to the broad, somewhat flattened shape characteristic of the genus.

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Habitat

Sandy soil environments suitable for excavation of burrow nests. Nests are typically constructed in open, well-drained areas where females can dig vertical tunnels 9–16 cm deep with radiating side burrows and .

Distribution

Holarctic distribution, occurring in the Nearctic (North America) and Palaearctic (Europe and Asia) regions. Records exist from Denmark, Norway, Sweden, the United States (including Vermont), and other northern temperate areas.

Diet

provision nest exclusively with () as food for their . Specific records include various fly ; some Crabro species show flexibility in prey selection while others exhibit more stereotyped preferences.

Life Cycle

Females are solitary nesters. Each constructs a nearly vertical burrow in sandy soil, with short side tunnels near the bottom terminating in individual . Each cell is provisioned with 4–9 paralyzed and sealed with sand and debris after a single is laid. Nests typically contain 1–10 cells. Development proceeds through egg, , , and stages within the sealed cells.

Behavior

nesting : females dig burrows, provision with , and seal them. Some exhibit behavioral flexibility in nest architecture and prey selection, while others show more stereotyped patterns. Temporal partitioning in daily activity has been observed between species. Females disperse excavated soil to conceal nest entrances and may use overhanging vegetation for additional concealment. visit flowers for nectar, particularly umbellifers such as wild carrot (Daucus carota), goldenrod (Solidago), and (Asclepias).

Ecological Role

of (), contributing to of fly . Limited by has been documented; the appears relatively to nest , possibly due to nest concealment behaviors.

Human Relevance

Potential agents for . Not known to be aggressive toward humans; are possible but uncommon. No significant to or structures.

Similar Taxa

  • AnacrabroSimilar appearance and shared tribe Crabronini, but Anacrabro hunts (, ) rather than , and lacks the strongly concave abdominal underside of Crabro.
  • EctemniusShared tribe Crabronini with similar body form, but Ectemnius has a flatter abdominal surface and different preferences.
  • LesticaSimilar overall appearance in Crabronini, but distinguished by abdominal shape and nesting differences.

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