Horntail-parasite
Guides
Megarhyssa
Giant Ichneumonid Wasps, Giant Ichneumons, Stump Stabbers
Megarhyssa is a genus of large ichneumonid wasps comprising 37 species distributed worldwide. Females possess extraordinarily elongated ovipositors—up to 14 cm in some species—that enable parasitism of wood-boring horntail larvae deep within tree trunks. The genus exhibits remarkable ecological specialization, with sympatric species partitioning host resources by ovipositor length, allowing coexistence through vertical stratification of host exploitation. These wasps are idiobiont ectoparasitoids, meaning they paralyze and consume their hosts without allowing further development.