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Fact Sheets: Commonly Observed and Asked About Insects and Spiders Found in Alberta

Banded Horntail (Urocerus gigas)

Banded Horntail
Banded Horntail
Photo CD 0023 3291 1601, Image #28 - Credit: Terry Thormin

INTRODUCTION

Any insect this big and with this large a "stinger" is bound to demand some attention and cause some concern. In actual fact the "stinger" is an ovipositor that is used only for laying eggs.

IDENTIFICATION

The large size of this insect (about 4 cm including the ovipositor), the rather cylindrical shape and the huge ovipositor, which can be up to 11 mm long, make this an easy insect to identify as a horntail. The two broad yellow bands around the abdomen identify it as a Banded Horntail. This is actually a type of primitive wasp.

DISTRIBUTION

In Alberta this insect is found in forested areas, particularly in the boreal forest and the foothills. It is distributed right across Canada and in the east, south to New Hampshire and in the west, south through the Rocky Mountains at least to northern Mexico. It is also found in northern Europe and Asia.

TIME OF YEAR

Banded Horntail adults are usually out in July, August and September.

HABITAT AND HABITS

The various species of horntails use their ovipositor for laying eggs in the wood of conifers. The Banded Horntail shows a preference for spruce. To be able to drill through solid wood the horntails need a very powerful and rigid ovipositor. Horntails tend to attack weak, dying or recently dead trees and thus are often found in logged areas or fresh burns. The larvae bore long tunnels usually in the first 4 cm of the wood. They can take 2 to 3 years to mature.

SIMILAR SPECIES

There are about six species of horntails in Alberta. Other than the Banded Horntail, the most commonly encountered species is the Black Horntail, Urocerus albicornis, which averages a bit smaller and is black in colour with black and yellow banded legs and antennae.

COMMENTS

Any insect this large with an ovipositor of this size usually causes some concern about the possibility of its stinging someone. The horntails, however, do not have an ovipositor that is modified for this purpose. The damage these species do to lumber is generally minimal, although they can introduce fungus that may cause significant damage.


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 Last update: August 31 2004