Giant Ichneumonid Wasps
Megarhyssa
Classification
- Phylum: Arthropoda
- Subphylum: Hexapoda
- Class: Insecta
- Order: Hymenoptera
- Superfamily: Ichneumonoidea
- Family: Ichneumonidae
- Subfamily: Rhyssinae
- Genus: Megarhyssa
Pronunciation
How to pronounce Megarhyssa: /ˌmɛɡəˈrɪsə/
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Images
Summary
Megarhyssa is a genus of giant ichneumonid wasps known for their long ovipositors and parasitic behavior towards wood-boring horntail larvae. These wasps are important for their ecological role in controlling pest populations and have unique reproductive behaviors that allow different species to coexist.
Physical Characteristics
Males 23-38 mm, females 35-75 mm (body), 50-110 mm with ovipositor. Body color ranges from dark brown to bluish black, reddish brown, and bright yellow. Variations exist among species, such as M. atrata having a bright yellow head and almost completely black body.
Identification Tips
Females are distinguished by their long ovipositors, which can be longer than their body length. M. atrata has a bright yellow head with a black body, while M. greenei, M. nortoni, and M. macrurus show yellow and brown striped color patterns. Males can be identified by their hyaline wings and various mesoscutum colors depending on species.
Habitat
Forested areas of North America, including deciduous forests. M. nortoni also resides in introduced regions such as South Africa, Australia, and New Zealand.
Distribution
Widespread across the United States and Canada, with specific distributions for each species: M. atrata from Nova Scotia to Georgia; M. greenei from Nova Scotia to Florida; M. macrurus in the western regions; and M. nortoni from Newfoundland to northern Georgia, west to Alaska and California.
Diet
Adult Megarhyssa typically feed on water droplets containing nectar, while larvae are ectoparasitoids of wood-boring horntail wasps.
Life Cycle
Megarhyssa larvae develop by consuming host larvae (Tremex columba). Adults emerge in the summer after pupating under the bark.
Reproduction
Females locate host larvae (e.g. Tremex columba) under tree bark, lay their eggs close to or on the larvae, which the Megarhyssa larva then consumes. Males often emerge first and may mate with females before they do.
Predators
Birds are known to predate on female Megarhyssa while they are drilling for oviposition.
Ecosystem Role
Megarhyssa serves as a biological control agent by regulating wood-boring horntail populations.
Collecting Methods
- Identifying host larval locations on trees
- Using light traps
Preservation Methods
- Ethanol immersion
- Pinning
- Setting in resin
Evolution
Megarhyssa has undergone allopatric speciation, allowing species to exploit different host depths with their varying ovipositor lengths, facilitating cohabitation in shared habitats.
Similar Taxa
Misconceptions
The ovipositor of Megarhyssa may be mistaken for a stinger, but it is primarily used for laying eggs, not for defense.
Tags
- Hymenoptera
- Ichneumonidae
- parasitoid
- entomology
- biodiversity