Functional morphology of the ovipositor in Megarhyssa atrata (Hymenoptera, Ichneumonidae) and its penetration into wood

Abstract 

Megarhyssa atrata (Pimplinae) is the largest species known amongst Hymenoptera. In its natural habitat, North America, it is a strict parasito¨ıd of Tremex columba (Hymenoptera, Symphyta, Siricidae). The para- site infests xylophagous host larvae buried in wood. The present work describes the complex movements of the ovipositor during oviposition and its flexibility ensuring the positioning of the stylus at the site of boring. These movements are made possible by the unfolding of the intersegmentary membranes (equipped with a secretory internal surface) and by the full rotation of abdominal segments 8 and 9. During this rotation, the stylus of the ovipositor pushes and extends the membranes completely which, as a result, form a translucent disc measuring 2 cm in diameter. The entry of the stylus into wood is helped by another secretion produced at the tip of the valvulae. This lytic secretion destroys wood fibers. With this set of adaptations, the hymenopteran can bore into a thickness of hard wood and reach its host larvae at a depth of 14 cm.

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Accepted: 2 May 1999

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Le Lannic, J., Nénon, JP. Functional morphology of the ovipositor in Megarhyssa atrata (Hymenoptera, Ichneumonidae) and its penetration into wood. Zoomorphology 119, 73–79 (1999). https://doi.org/10.1007/s004350050082

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Keywords

  • Natural Habitat
  • Internal Surface
  • Wood Fiber
  • Large Species
  • Abdominal Segment