Megarhyssa greenei
Viereck, 1911
Greene's Giant Ichneumonid Wasp
Megarhyssa greenei is a large ichneumonid known from the United States and Canada. Females possess an elongated ovipositor used to parasitize larvae of the Tremex columba, commonly called the pigeon horntail. The is frequently confused with the similar Megarhyssa macrurus but differs in relative ovipositor length and facial markings. emerge from under tree bark after approximately one year.
Pronunciation
How to pronounce Megarhyssa greenei: /mɛɡəˈrɪsə ˈɡriːnaɪ/
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Identification
Distinguished from Megarhyssa macrurus by ovipositor length (slightly >1x body length vs. ~2x body length in macrurus), reduced dark wing markings, and absence of dark facial striping. These characters require close examination and comparison with reference specimens or images.
Images
Habitat
Associated with dead and dying hardwood trees where larvae occur; females oviposit into wood containing Tremex columba larvae. Specific microhabitat preferences beyond host-related requirements are not documented.
Distribution
United States and Canada. GBIF records indicate presence in Vermont and other US locations. Precise range boundaries are not well-documented in available sources.
Diet
Larval stage feeds on Tremex columba larvae. feeding habits are not documented in available sources.
Host Associations
- Tremex columba - Pigeon horntail ; larvae develop inside decaying hardwood
Life Cycle
Female locates larva within wood and deposits nearby or directly on it. Larva consumes host, pupates under tree bark, and emerges as approximately one year later. Specific details of egg and early larval stages are not documented.
Behavior
Females use elongated ovipositor to reach larvae deep within wood. The process involves locating host larvae in decaying hardwood and penetrating wood to deposit . Specific behavioral details regarding host location cues or oviposition mechanics for this are not documented.
Ecological Role
of Tremex columba, contributing to of this wood-boring . Role in broader processes such as nutrient cycling or dynamics is not documented.
Human Relevance
No documented direct interactions with humans. Occasionally encountered by observers in forested areas due to large size and conspicuous ovipositor of females. Not known to be economically significant or medically important.
Similar Taxa
- Megarhyssa macrurusVery similar appearance; distinguished by longer ovipositor (~2x body length vs. slightly >1x), more extensive dark wing markings, and presence of dark facial striping
- Megarhyssa atrataAnother large congeneric ichneumonid with elongated ovipositor; differs in having predominantly black body with yellow
More Details
Taxonomic history
Described by Viereck in 1911. The epithet greenei presumably honors an individual, though the honoree is not identified in available sources.