Orussidae

parasitic wood wasps, parasitoid wood wasps

Genus Guides

2

is a small of approximately 93 extant of . They occupy a pivotal phylogenetic position as the sister to the megadiverse , indicating that evolved in the common ancestor of Orussidae + Apocrita. are rarely encountered, typically found on sun-exposed dead wood where females use vibrational sounding to locate concealed . Larvae are the only sawfly larvae known, acting as parasitoids of wood-boring beetles and other Hymenoptera.

Orussus by (c) Daniel Linzbauer, some rights reserved (CC BY), uploaded by Daniel Linzbauer. Used under a CC-BY license.Orussus by (c) Benjamin Burgunder, some rights reserved (CC BY), uploaded by Benjamin Burgunder. Used under a CC-BY license.Orussus by (c) Justin Williams, some rights reserved (CC BY), uploaded by Justin Williams. Used under a CC-BY license.

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.

Identification

2–23 mm, predominantly black with some metallic; males have 11 antennal articles, females 10 with modified articles for vibrational sounding. insert near lower edge of close to , unlike other . bears distinctive corona of erect teeth around frontal ocelli (shared only with Stephanidae). Wings held at rest by cenchri; reduced cross- compared to other basal Hymenoptera. Ovipositor several times body length, coiled within body from to prothorax and back. Globular head with orthognathous mandibles lacking evident teeth. Some species have red or abdomen, white or golden pilosity, or white leg spots.

Images

Habitat

Dead wood in forests, particularly sun-bleached, bark-stripped logs and standing dead trees. Found in both coniferous and deciduous forests, often at forest edges, meadows, or openings. Thermophilous; active during hottest hours of day.

Distribution

Widespread but locally rare: Holarctic, Oriental, Afrotropical, Neotropical, and Australasian regions. North America: 9 in 4 north of Mexico. Europe: Orussus abietinus historically recorded in Britain. Ophrynon to California. Orussobaius predominantly Australasian with 7 of 9 species in Australia.

Seasonality

active during warmest periods of day; seasonal activity varies by region. Rarely collected due to thermophilous and cryptic habits.

Host Associations

Life Cycle

Female lays elongate with small expansion and long expansion, coiled on or near . In Guiglia schauinslandi, larva lives externally for first two instars, then enters dead host. Larva white, subcylindrical, weakly sclerotized with reduced or absent and legs; well-developed sclerotized ; body segments bear transverse rows of 8–10 backward-pointing spines presumably aiding locomotion through tunnels.

Behavior

Females locate concealed larvae using vibrational sounding: tap tips against wood surface and detect reverberations through subgenual organ in fore tibiae. After host location, female drills into wood with long ovipositor to oviposit. run rapidly and erratically on dead wood, changing direction abruptly; capable of jumping.

Ecological Role

of wood-boring insects; likely contribute to regulation of of forest pests including jewel beetles, longhorn beetles, and wood wasps.

Similar Taxa

  • StephanidaeBoth have corona of erect teeth around frontal ocelli, but Stephanidae lack cenchri and have -waisted petiole separating mesosoma and metasoma
  • SiricidaeBoth are wood-associated , but Siricidae are herbivorous with fungal , not ; have cylindrical bodies and different ovipositor structure
  • Carpenter ants (Camponotus)Orussus with dark wing bands and folded wings superficially resemble ants; distinguished by globular , antennal insertion near mouth, and jumping

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Sources and further reading