Spathius

Nees, 1818

Species Guides

1

Spathius is a of doryctine wasps in the Braconidae. within this genus are larval of wood-boring beetles, with several species introduced to North America as agents for the emerald ash borer (Agrilus planipennis). The genus includes both native and introduced species that exhibit -specific relationships with their hosts.

Spathius by (c) Katja Schulz, some rights reserved (CC BY). Used under a CC-BY license.Spathius by (c) Saryu Mae 前 朝琉, some rights reserved (CC BY), uploaded by Saryu Mae 前 朝琉. Used under a CC-BY license.Spathius by (c) Mark Richman, some rights reserved (CC BY), uploaded by Mark Richman. Used under a CC-BY license.

Pronunciation

How to pronounce Spathius: //ˈspeɪθiəs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

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Habitat

Forests and woodlands containing trees; specifically associated with ash trees (Fraxinus spp.) infested by wood-boring beetles. Some inhabit concealed galleries within dry timber and wood products.

Distribution

Widespread across the Palaearctic, Oriental, and Nearctic regions. Native range includes northeastern China, the Russian Far East, and India. Several have been introduced to North America (United States and Canada) for purposes.

Diet

Larvae are ectoparasitoids of wood-boring larvae. Documented include emerald ash borer (Agrilus planipennis), Hylurgopinus rufipes, and various bostrichid beetles including Heterobostrychus aequalis, Dinoderus brevis, Dinoderus minutus, and Dinoderus ocellaris.

Host Associations

Life Cycle

Idiobiont ectoparasitoid development. Females drill through bark using a long ovipositor to reach larvae concealed in wood, then deposit on or near the host. Larvae feed externally on the host, consuming tissue before pupating within the host gallery. Some exhibit long-lived preimaginal stages capable of surviving extended periods within dry wood.

Behavior

Females use volatile chemical cues from -infested trees to locate hosts. Ovipositor length varies among , determining the maximum bark thickness through which hosts can be reached. Spathius galinae possesses an ovipositor approximately twice as long as that of Tetrastichus planipennisi, enabling of larger diameter trees. Females deposit clutches of approximately 20 on host larvae.

Ecological Role

agent of wood-boring beetles. As ectoparasitoids, they reduce of pest beetles that damage forest and urban trees. Some may compete with native where ranges overlap.

Human Relevance

Used in programs to manage emerald ash borer, an pest that has killed millions of ash trees in North America. Spathius galinae has shown particular promise, with rates reaching 49% and successful establishment in wild within two years of release. do not sting humans.

Similar Taxa

  • Tetrastichus planipennisiBoth are larval of emerald ash borer used in ; distinguished by shorter ovipositor in Tetrastichus (1.5–2.5 mm vs. longer in Spathius), endoparasitoid development in Tetrastichus versus ectoparasitoid in Spathius, and different timing
  • Oobius agriliBoth are introduced of emerald ash borer; Oobius is an parasitoid with much smaller size and different stage targeted
  • Phasgonophora sulcataNative North American of wood-boring beetles; shows opposing response to ash compared to introduced Spathius galinae, with negatively associated with high ash density

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