Whitespotted Sawyer

Illustration by Adelaide Tyrol

If, when quietly wandering around outdoors, you have ever heard and tried to track down a rhythmic, grating sound, thinking you were in search of a small rodent or perhaps a cricket, only to find that the noise comes from within a dead log, the noisemaker might well be the larva of the whitespotted sawyer. Its chewing noise is described as resembling a sawyer at work and is the source of its name. A small stream of finely ground, sawdust-like fragments can often be found coming from a hole in a noisy, dead, softwood log.

This wood-boring beetle, found throughout the Northeast and in the Northwest to Alaska, prefers to feed on white pine, but all the spruces and balsam fir can also serve as hosts.

In the spring, adult beetles emerge from their pupal cells in logs and, before they begin mating, feed on coniferous foliage and twigs, often killing small branches. Overall, damage by adult beetles is not usually significant.

After feeding on foliage for awhile, male beetles scout around for a suitable host tree, usually one that is dead or nearly dead, and defend a desired territory from other males. Larger beetles tend to occupy the best real estate and, perhaps for that reason, females have been found to prefer larger males. Piles of pine logs, waiting to go to the sawmill, are a whitespotted sawyer’s heaven.

In field-trapping experiments, female whitespotted sawyers have been found to be attracted by pheromones from bark beetles, suggesting that insect chemistry is capable of broadcasting to the whole tribe, not just one’s own species. Neither bark beetles nor whitespotteds are capable of surviving on a healthy tree, but when two or more insect species join the attack, it may put a stressed tree over the edge.

After mating, female whitespotted beetles chew slits into the bark of the host log and deposit one or more eggs in each slit. The larvae hatch out in about two weeks and begin feeding, making their way through the phloem and into the cambium, where they feed for several weeks. As the larva grows, its galleries become wider and deeper, forming grooves in the surface of the wood.

When young, the larvae do not penetrate deeply into the wood, but they do introduce blue-stain and other fungi, which either have been delivered by the adult along with her egg or have landed on the holes the female excavated in the bark. Except for stain, little harm is done in the first few months of beetle occupancy, because the bark is removed at the sawmill.

As the larvae grow, they head towards the center of the log, where their larger tunnels are most unwelcome in any normal wood product: at up to two inches long and 3/8 of an inch in diameter, they leave quite a tunnel behind. Dead wood is not the most nutritious food, and in the North it normally takes two years for a whitespotted sawyer to complete its life cycle. Cannibalism is commonly engaged in by larvae, an interesting way to improve the quality of your diet.

Although adult beetles are most active on sunny days, the egg slits are cut on the sides and bottoms of logs, away from direct sunlight. Still, they strongly prefer logs in the sun, so if you need to leave a pile of pine logs out in the summer, covering them with a nice layer of slash to shade them will reduce their appeal. Logs piled in the shade have far fewer beetle eggs as well. Shade, together with slash covers, is even better.

At up to one inch long, the adults are big, clumsy fliers with oversized antennae and a tendency to plop down for a rest just about anywhere, making them easy to spot and catch on sunny summer days. Though smaller than the dreaded Asian longhorned beetle (ALB), they are in the same family – the Cerambicidae – and share the same general shape and format.  Fortunately, whitespotted sawyers have a nice little diagnostic feature that can bring instant reassurance: they have a small white spot at the very front edge of their wings, right in the middle, just aft of the thorax. Both the whitespotted and the ALB may have numerous other spots on their outer wings, but the position of the spot on the less-threatening species allows for instant ID. Another beetle sometimes confused with the ALB, the northeastern sawyer (Monochamus notatus), is as large as the ALB, but it is light in color, mottled, and has no distinct spots.

 
Discussion
  1. Sandra Walker → in Madison, Maine
    Sep 03, 2009

    I saw the story on the news tonight about the Asian Longhorn and thought it was the beetle we had here about 11 or 12 years ago, but found on you website that it is the Whitespotter Sawyer. My husband says they are still in the area but I haven’t seen one in a long time. They are in the pine trees behind our house. And they do bite and it is quite painful. I suffered no ill effects from it, but thought you should know this.

  2. Larry Smith → in Winter Harbor, ME
    Sep 18, 2009

    Sighted 4 September 2009.  Have photo I can e-mail if you need it.

  3. James → in Berlin, MA
    Jun 22, 2011

    Had one enter my bedroom somehow and kept it in my handy dandy *bugzooka* for a few days, after identifying it as definately NOT a ALB let it go to freedom on day 3, unfortunately HE took off too quickly to capture a good photo. I have been living here my whole life and this is the first I’ve ever seen, good or bad sign?? 26yrs old. Sighting June 19th, 2011

  4. Michael → in Millinocket, ME.
    Jul 25, 2011

    The first time I ever saw a Spotted Sawyer was in the mid to late 90’s in Greenville ME. I did hold it but it never bit me. I have seen them numerous times since then in the MooseHead region of ME, never have been bitten. I recently moved to Millinocket ME. from MA. In June I saw the beetle again on my car in Millinocket. My neighbor was with me and said he had been bitten more than once by these beetles. He said they were more painful than a bee sting.

  5. Amanda → in Ringgold, VA
    Apr 16, 2012

    I saw one of these for the first time last night. I was not sure what type of insect it was until I looked it up. It bit me on the inside of my arm. And yes, it did hurt worse than a bee sting. I am allergic to bees and oddly enough I had the same reaction to the beetle bite. My arm started swelling up and this morning I am left with a very defined bite mark with about a 1/2 inch red circle all the way around it. It still hurts. I took pictures of the bite mark if anyone is interested.

  6. Ruby Coolidge → in East Bethel, Maine
    Jul 08, 2012

      I have caught 2 of these Whitespotted Sawyer Beetles just recently , Both males. they are huge . I have a lot of pine trees around here but I don’t wish to get bitten..I also don’t want my great grandsons to get bitten….

  7. susan in northern minnesota → in backus, minnesota
    Jul 23, 2012

    I just took a photo, as I love interesting insects and all other outdoor things, and was gratified to find out what kind of bug I’d found. Glad I didn’t try and hold it, I had no idea it would bite! Thanks for the info.

  8. Angelique → in Spokane, WA
    Jan 21, 2013

    Ahhh, we’ve got these buggers all over my mother’s property, rural pine forest with some firs, near the river. They get quite noisy in the summer! but I’ve never had one land on me or bite me, thankfully. Sounds painful!

  9. Jennifer → in Alberta, Canada
    Jun 17, 2013

    We live in northern Alberta in Canada and these bugs are everywhere once summer comes. My son gets bitten at least once a summer by these things and it turns really red, swells and the skin turns very hot. After a couple of days the bite starts to ooze clear fluid for quite a few days. I hate them!

  10. Randi → in Alberta, Canada
    Jun 28, 2013

    These things have been the centre of many a nightmare for me! I moved to Alberta in 1988 and 3 days later spotted my first one…. I have been bitten but I’m scared more of them just landing on me! Jennifer is right! They are everywhere in Alberta and I have not been able to enjoy a summer since I was 11 years old! I hate these things sooooooooooo much! I am looking for info on their life cycle and such so I can enjoy some summer this year!

  11. Ovine → in Highland Co. VA
    Aug 14, 2013

    Anyone have any idea how this creature makes so much noise? I could hear the gnawing sound inside a dead spruce tree a hundred feet away from the tree. If it is actually thousands of the grubs, how do they keep in sync?

  12. Patricia Chesnut → in United States
    Aug 22, 2013

    My question is…how do you get rid of them? Cornell Cooperative Extension identified them in our siding…don’t want them there!

  13. Kevin Brownlee → in Ontario, Canada
    Aug 26, 2013

    I had one get into my croquet shoes and bite me, it took a small chunk of flesh, about the size of the tip of a pencil lead. It bit me in my middle toe, it felt like I had been stung by a hornet or wasp. Within the first half hour my toe was double the size and red, within the hour my foot was 1.25 the normal size and feeling very swollen. I took a antihistamine and the following day the swelling started to go down

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