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Family Siricidae - Horntail Wasps

What is the giant insect? - Tremex columba - female Urocerus Californicus? - Urocerus albicornis Tremex columba - female Eriotremex formosanus Siricidae, Pigeon Tremex - Tremex columba Xeris indecisus?  - Xeris indecisus - female Horntail wasp of some kind? - Tremex columba Tremex columba?  - Tremex columba
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon ("Symphyta" - Sawflies, Horntails, and Wood Wasps)
Family Siricidae (Horntail Wasps)
Other Common Names
Wood Wasps (more prominent outside of the US)
Explanation of Names
The common name of horntails refers to their abdominal spine
2 subfamilies, with 28 spp. in 5 genera in our area and ~120 spp. in 10 genera worldwide(1)
Size varies tremendously: adults of the same species may vary from 1 to 5 cm
Mesonotum not divided by a transverse groove between bases of fore wings. Protibia with 1 apical spur. Last tergum of female and last sternum of male each with apical, median, cylindrical projection with concave tip. Pronotum in lateral view with a horizontal dorsal surface and with a vertical, concave anterior surface; pronotum in dorsal view with posterior margin strongly concave, with medial length about one-third lateral length.
Both sexes have a short abdominal dorsal projection (horn) that gives them their common name. Females also have an ovipositor in a sheath, placed ventrally in the abdomen.
Color is useful in identification.
Keys to genera and spp. in(1)
FL fauna treated in(2)
forests of the Northern Hemisphere south to Cuba, n. Central America, India, New Guinea, and n. Africa (2 spp. are known from tropical Africa)(3)
Wood (Tremicinae mostly on hardwoods; Siricinae, on conifers); larvae require a symbiotic fungus to digest wood(3). It is a complex interaction between three organisms: the wood wasp, a symbiotic wood-decaying fungus, and the host tree.
Life Cycle
larval development may take 1 to 3 years to complete depending on species and climate(3).
Males emerge first and disperse, preventing inbreeding.
A fungal inoculant from Cerrena unicolor is deposited along with the eggs. This fungus is stored in special abdominal pouches in each female. The fungus tenderizes and enriches the wood for the larva.(4)
Some are serious pests of trees and spread as larvae with lumber trade.
The most important predators and parasitoids are the ichneumonid wasp Megarhyssa and some nematodes. Others include Ibalia.
Horntails do not sting: what looks like a sting is the ovipositor the female uses to lay eggs in wood
Females more abundant than males
Adults fly mostly in bright sunshine
Nematodes depend on wood wasps for distribution from tree to tree. There are 2 types that partner with wood wasps, a fungus-feeding one and a larva parasite. The parasitic one (Deladenus siricidicola) moves to the eggs and testes, sterilizing the wasps but not killing them. The wasp continue with their life, laying sterile eggs and spreading the nematode throughout the trees and to other wood wasps.(4)
Works Cited
1.Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere
Schiff, N.M., Goulet, H., Smith, D.R., Boudreault, C., Wilson, A.D., and Scheffler, B.E. 2012. Canadian Journal of Arthropod Identification No. 21: 305 pp.
2.The Siricidae (Hymenoptera: Symphyta) of Florida
Leavengood J.M., Smith T.R. 2013. Insecta Mundi 0309:1-16.
3.Guide to the siricid woodwasps of North America
Schiff N.M., Valley S.A., LaBonte J.R., Smith D.R. 2006. USDA Forest Service, Forest Health Technology Enterprise Team, Morgantown, WV. 101 pp.
4.Hidden Company that Trees Keep: Life from Treetops to Root Tips
James B. Nardi. 2023. Princeton University Press.