Megarhyssa macrurus icterosticta

Distinguished from M. atrata by smaller male size, more brown than black body coloration, and clear wings with well-developed costal spot (versus smoky wings with narrow spot in M. atrata). Females distinguished by ovipositor length relative to body and depth of wood penetration during oviposition; M. macrurus females target shallower horntail larvae than M. atrata.

Medium to large ichneumon wasp. Males: body predominantly brown with black markings, wings clear with well-developed dark spot on costal margin. Females: extremely long, thread-like ovipositor (often exceeding body length), body coloration similar to males. Smaller overall than M. atrata males, which have more extensive black coloration and smoky wings with narrow costal spot.

Deciduous forests with declining or dead hardwood trees, particularly sugar maple (Acer saccharum) and other species supporting Tremex columba populations. Requires standing dead or dying wood with intact bark for oviposition substrate.

Eastern North America; documented in Missouri and surrounding regions. Exact range boundaries relative to nominate subspecies undetermined from available sources.

Adult activity observed in spring; specific flight period not documented in sources.

• Tremex columba - parasitoidLarval parasitoid of woodboring pigeon horntail larvae; females target larvae at shallower depths in wood than M. atrata

Males exhibit 'tergal stroking' behavior: bending abdomen forward beneath body and rubbing abdominal tip against bark, sometimes inserting tip into bark cracks. Males aggregate on tree trunks where females are emerging or ovipositing. Function of tergal stroking unknown; possibly related to sex discrimination of emerging wasps or increasing encounter rate with virgin females.

Primary parasitoid regulating populations of Tremex columba. Coexists with larger congener M. atrata through resource partitioning: M. macrurus females parasitize horntail larvae at shallower wood depths, while M. atrata females access deeper larvae with longer ovipositors.

• Megarhyssa atrataSympatric congener with larger males (more black, smoky wings with narrow costal spot), larger females with longer ovipositors targeting deeper horntail larvae; both species aggregate at same trees but partition resources by depth

• parasitoid
• ichneumonidae
• woodboring
• resource partitioning
• sexual dimorphism
• Missouri

• BugGuide
• iNaturalist taxon
• Multiple Megarhyssa males | Beetles In The Bush