Horntail
| Horntails | |
|---|---|
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| Eriotremex formosanus, Blount County, Tennessee | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Suborder: | Symphyta |
| Superfamily: | Siricoidea |
| Family: | Siricidae |
| Genera | |
Horntail or wood wasp is the common name for any of the 150 non-social species of the family Siricidae, of the order Hymenoptera, a type of xylophagous sawfly. This family was formerly believed to be the sole living representative of the superfamily Siricoidea, a group well represented in Paleogene and Mesozoic times, but the family Anaxyelidae has been linked to this group. There are ten living genera placed in the family, and an additional three genera described from fossils. The last tergite of the abdomen has a strong, projecting spike, thus giving the group its common name (the ovipositor is typically longer and also projects posteriorly, but it is not the source of the name). A typical adult horntail is brown, blue, or black with yellow parts, and may often reach up to 4 cm (1.6 in) long. The pigeon horntail (Tremex columba) can grow up to 5 cm (2.0 in) long (not counting the ovipositor), among the longest of all Hymenoptera.
Female horntails lay their eggs in trees. The larvae bore into the wood and live in the tree for up to two years, possibly more. They typically migrate to just under the bark before pupation.
The spiral groove on the ovipositor is visible on the photograph but not easily to the naked eye.
The smaller horntail (Sirex noctilio) is only about half the size of the greater horntail, with pale brown legs and the rest metallic blue-black. It pierces the bark of pines to lay eggs. The smaller horntail ovipositor is very similar to the greater horntail, which is described as:
"as stiff and straight as a needle, polished black, with slight notches in the pointed half. It is hinged, to permit of its being turned at right angles to the body. . . the female selects a tree that is not too healthy, and settles on the bole; then, turning down her boring instrument on its hinge, she drives it through the thick bark to the solid wood."
When we consider the small size of the insect, it seems remarkable that she should have muscular power sufficient to force that slight auger through such resistant material; but that the boring imposes no strain upon her is shown by the fact that she may make several experimental punctures without an egg passing; apparently the wood reached is not quite suited for her purpose, so she tries another spot. Often her operations are upon a tree that has been felled for the builder's use; and by this means the new generation finds its way at times into our homes. Having satisfied herself that at last she has found the proper conditions under which a larva could exist, she passes an egg into the wood; then she repeats the process at some other spot on the same tree or log.
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Wikipedia