Parasitic Wood Wasps

Orussidae

Classification

Pronunciation

How to pronounce Orussidae: /ɔˈrʊsɪdeɪ/

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

Images

Oryssus thoracicus by the Smithsonian. Used under a CC0 license.
Oryssus modestus by the Smithsonian. Used under a CC0 license.
Oryssus hopkinsi by the Smithsonian. Used under a CC0 license.
Oryssus thoracicus by the Smithsonian. Used under a CC0 license.
Oryssus relativus by the Smithsonian. Used under a CC0 license.
Oryssus hopkinsi by the Smithsonian. Used under a CC0 license.

Summary

Orussidae, or parasitic wood wasps, represent a small family of sawflies with unique larval stages as ectoparasitoids of wood-boring insects. They play a crucial ecological role and have a complex life cycle involving host detection through vibrations.

Physical Characteristics

Adults are 8-14.5 mm long, predominantly black, some metallic; red thorax or abdomen and white/golden pilosity in some species; body sclerotized with species-specific microstructure. Larvae are white, subcylindrical, weakly sclerotized with a distinct head capsule, mandibles well developed.

Identification Tips

Look for the groove separating the mesoscutum from the axilla on either side of the scutellum, the single submarginal wing cell, and the dorsal crown of backward-pointing teeth around the median ocellus.

Habitat

Found on dead tree trunks where host larvae reside; species are thermophilous and active during the hottest hours.

Distribution

Approximately 7 species in North America and Canada; 85 species worldwide.

Diet

Larvae are ectoparasitoids of xylobiontic insect larvae, primarily targeting Buprestidae, but also Cerambycidae, Xiphydriidae, and Siricidae.

Life Cycle

Female wasps locate host larvae via vibrations, drill into wood with a long ovipositor, and lay eggs; larvae live externally for part of development before entering host.

Reproduction

Females use vibrations to locate concealed host larvae for oviposition; eggs coiled on/in host material.

Ecosystem Role

Key role in parasitism of wood-boring insects, contributing to the regulation of beetle populations.

Collecting Methods

  • Hand collection from host sites on dead wood

Preservation Methods

  • Ethanol
  • Pinning specimens
  • Storage in entomological envelopes

Evolution

Orussidae are the sister taxon to Apocrita; parasitism evolved in their common ancestor rather than solely in Apocrita.

Similar Taxa

Misconceptions

Often confused with other types of sawflies or wasps due to similar morphology.

Tags

  • Hymenoptera
  • Wood Wasps
  • Parasitic Insect
  • Xylobiontic Insect
  • Ectoparasitoids