Longhorned Beetles

The Asian longhorned beetle has been getting a lot of attention. I have received a number of phone calls from people who think they have caught one of these beetles and are wondering what to do. We have a number of native beetles that look similar to the Asian beetle and one in particular – the Whitespotted pine sawyer beetle looks quite similar. All of the calls I have received turned out to be pine sawyer beetles.

Both of these beetles are black with white spots and have long antennae. The Whitespotted pine sawyer is distinctive because it has a prominent white spot at the base of the wing covers where they join. Looking at the beetle from above, this white spot is in the centre of the wings just behind the head area. The Asian beetle lacks this spot. The Asian also has more distinct (up to 20) white spots on its’ wing covers. Both beetles vary in size from about 19 – 35 mm or (¾ - 1 ¼ inches). These beetles have very long antennae, with those of the males being twice as long as the body.

Asian longhorned beetles feed on healthy broad leafed trees such as maple, elm, ash, poplars, alder and willow. They do not feed on coniferous or evergreen trees. Whitespotted pine sawyer beetles feed only on coniferous trees such as balsam fir, various pines and spruce. They generally attack weakened or recently dead conifers and freshly cut logs. It is the larvae of longhorned beetles that do the major damage to trees. They will bore through the tree trunk leaving large round holes. The larvae can be up to 5cm (2 inches) long. Adults cause damage by feeding on the foliage, tender bark and twigs.

Whitespotted pine sawyer beetles are quite common. When you buy building lumber that has round holes in it there is a good chance that the culprit was the pine sawyer. While it doesn't seem to happen as much any more, it was not uncommon in the past for the larvae to still be alive in wood such as 2X4’s. I have had a number of calls over the years where the adult beetles have chewed their way out through drywall much to the consternation of the homeowner. They do not re-infest wood in the home.

Fire wood is another good place to find a variety of native longhorned beetles. Sometimes you can hear the larvae in the wood. I have removed more than one free load of fire wood from a homeowner whose definition of communing with nature doesn’t include listening to fat beetle larvae munching through wood.

A good web site to check out a variety of beetles and other insects that may be confused with the Asian longhorned beetle.