Rhyssa

Gravenhorst, 1829

Species Guides

6

Rhyssa is a of large ichneumon wasps in the Rhyssinae, characterized by exceptionally long ovipositors used to parasitize wood-boring larvae. The genus name derives from Greek meaning "wrinkled." in this genus are of siricid woodwasps and related wood-boring insects, with females drilling through timber to locate and oviposit on concealed deep within wood. They are distributed across Europe, North Africa, the Near East, North America, the Indomalayan realm, and Australia.

Rhyssa by no rights reserved, uploaded by Lisa Ferrel. Used under a CC0 license.Rhyssa lineolata by (c) Owen Strickland, some rights reserved (CC BY), uploaded by Owen Strickland. Used under a CC-BY license.Rhyssa alaskensis by no rights reserved, uploaded by Andy Kleinhesselink. Used under a CC0 license.

Pronunciation

How to pronounce Rhyssa: /ˈrɪsə/

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Identification

Rhyssa are large ichneumon wasps with extremely long, hair-thin ovipositors (terebra) that can exceed body length. They can be distinguished from similar large ichneumonids by their placement in Rhyssinae, though exact species identification requires examination of maculation patterns, coxal and leg coloration, and body proportions. They may be confused with Podoschistus, which belongs to subfamily Poemeniinae and has different associations (wood-boring beetles rather than woodwasps). Rhyssa species show geographic variation in maculation, with southwestern European and North African forming a distinct group from other populations.

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Habitat

Forested areas with coniferous or broadleaf trees containing wood-boring larvae in timber. Females are observed climbing on tree trunks where hosts are present. Specific associations vary by host tree , with some linked to dark, fissured-barked trees and others to lighter-barked species.

Distribution

Europe (including Scandinavia), North Africa, the Near East, the (North America), the Indomalayan realm, and the Australian region. Specific distribution records include Denmark, Norway, Sweden, Vermont (USA), and central Louisiana (USA).

Host Associations

Life Cycle

Females locate larvae concealed in wood, paralyze them by stinging, and lay upon them. The larva consumes the host over approximately five weeks, passing through four larval instars before . Development has been tracked in situ using X-ray techniques to observe stages within host galleries without disturbing the wood.

Behavior

Females use a combination of long-range olfactory attraction to fungal of their (particularly Amylostereum areolatum) and short-range searching with and ovipositor to pinpoint host location. They drill through wood with their ovipositor to reach host larvae. Host location is not certain; females may probe extensively before successfully locating a host. timing varies by and region.

Ecological Role

of siricid woodwasps, which are pests of coniferous timber. Rhyssa function as agents that regulate woodwasp . They participate in a tri-trophic ecological system: parasitoid affect insects, which in turn affect their host plants.

Human Relevance

Used in programs, including shipment of Rhyssa persuasoria to New Zealand for control of Sirex noctilio. Subject of (Deladenus sp.) that reduce and longevity, with implications for efficacy.

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