Horntails

Horntails are a large family of wasp-like insects whose larvae are woodborers in either hardwoods or coniferous trees.

The name horntail is given to these insects because of the horny spear-like plate on the last segments of the abdomen. This horny spear is its egg laying apparatus (ovipositor). Neither sex stings or bites people. Horntails are also called wood wasps or Siricidae. Our most common species in New York State is the Pigeon tremex, Tremex columba.

Adult horntails have a heavy body that is cylindrical in shape, and usually blackish or metallic blue with yellow and red markings. The males are generally smaller than the females, but often more colorful. Both sexes have four clear wings. Adults are usually 1 inch or more in length and are strong fliers. Larvae are milky white, softbodied and legless, ranging up to 1 3/4 inches in length, and are found tunneling in the wood.

Horntails are an unusal because their biology that is not typical of most Hymenoptera. The larvae feed in dead logs much like wood-boring beetle larvae. The adults resemble wasps but they have a wide waist and therefore a cylindrical body. Adults are often found ovipositing on logs.

Life Cycle: Adult horntails are attracted to weakened, dying, or recently cut wood. The female inserts her ovipositor as much as 3/4 inch into the wood to lay her eggs. Eggs are laid singly, but each female is capable of laying 300 to 400 eggs. After 3 to 4 weeks, eggs hatch and the larvae chew their way into the sapwood and heartwood.

The tunnels are bored during the 2 to 3 year time span of the larval stage. Tunnels may be from 1 to 2 feet in length. As the larvae chew, the tunnels become packed with a sawdust-like material, making them difficult to see to the uninformed eye. Pupation occurs in the tunnel made by the larva, in a parchment-like cocoon. The adults emerge in August and September, and are often seen resting on a tree stump or freshly cut pile of logs.

One interesting aspect of the life of Tremex columba is that there is a spectacular looking ichneumon wasp parasitoid that attacks it. The ichneumon wasp female drills her long ovipositor into the wood where the horntail larva is working. The ichneumon’s ovipositor enables it to drill into the wood 3 to 4 or more inches to reach the horntail larva. She lays her eggs either on or near the horntail and the parasitic larva begins to feed. After pupation, the ichneumon chews its way out of the bark and may occasionally be seen resting on a tree. It is conspicuous because of its very long ovipositor (3 or more inches long).

Damage : The wasps bore in the wood of trees, and though they seldom do great damage to the tree, they may be present in the wood when the tree is cut into lumber. Within a year or so after house construction, horntail wasps may bore out of the infested wood and may even bore through sheetrock and similar materials which are next to the infested wood.

Horntails are not structurally damaging unless they emerge in large numbers. They do not attack dry, finished wood, and so they should not reinfest the wood of the house. Horntails may also be brought into the house in firewood

Eventually the damaged foliage becomes papery, wilts and drops prematurely. Thrips produce large quantities of a varnish-like excrement which collects on leaves, creating an unsightly appearance.

Management : Wood wasps are likely to occur anywhere that infested timber is used for construction. Even though salvaged timber is adequate for restricted, lower grade construction purposes (such as studs and subflooring), it is not valuable enough to warrant kiln-drying. Kiln-drying or vacuum fumigation of lumber is the only effective way to kill wood wasp larvae that have survived milling operations, but treatment is costly.

Even though wood wasps can be a noisy, scary nuisance, they are not a threat to anyone or anything. Waiting out the life cycle and repairing cosmetic damage is about all that can be done in an infested building. Once emerged, wood wasps will not reinfest harvested lumber.

If you ever have any bug related issues in New York City, feel free to call us either at Beyond Pest Control. Once again, and I can’t stress this enough we are on call twenty four hours a day seven days a week to kill those bugs, we aren’t kidding whether you call us at 9 am or midnight we will be available to take your call and either get rid of the bug infestation, or answer any questions you may have concerning the bug issue. I can honestly guarantee that there will be someone to answer that call. We make it our business to make you bug free!

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