[Stinging Insects] Sucking Up Stingers

y client was not having a good day. Dozens of
European hornets had been showing up inside her house over the past week, and the inevitable finally happened — she had taken a sting on her foot and was, literally, hopping mad. The giant wasps could be found in almost every room, but mostly in the unfinished basement.

It didn’t take too long to figure out what was going on. An inspection from the outside revealed the hornets were getting into their concealed nest by squeezing through a gap under the fascia board. A visit to the attic could not pinpoint the nest’s precise location, but attraction to remote sources of light is typical for social wasps living in dark building cavities. The tendency to wander away from the nest is further reinforced by trail pheromones laid down by those who have boldly gone before. Most of the hornets ended up in the basement simply because the continuous void down the exterior wall was the path of least resistance.

What’s the safest way to treat something like this? The "Case of the Hazardous House Hornets" illustrates one of several classic situations involving stinging insects where the "best practice" professional control solution includes the use of a vacuum. Suction has proved handy for a wide range of pest problems, from cockroaches to prairie dogs, and it’s often suggested as a technique for social wasps as well. It’s quite a showstopper when it’s done correctly, but before you rush out and stir up a hornets’ nest, here’s a crash course on the basics.

SUCTION SCENARIOS. Since nests that are exposed or in the ground can be so easily killed even with drugstore aerosols, there’s usually no reason to use a vacuum for them. But there are important exceptions. The first is if your client is willing to pay a premium price for the extra time and effort it takes to render a non-pesticide treatment. Another circumstance would be when a colony is located where young children play. Even products with an extremely quick knockdown tend to leave dozens of dying wasps writhing and crawling on the ground nearby, particularly when dropping out of aerial nests. Dozens more will careen through the air in the general vicinity after returning to a treated nest and getting a whiff of the pesticide. If there is a chance that stricken wasp and inquisitive child might interact at any point, it simply makes good sense to use a vacuum before you apply your chemical, to totally remove as many of the insects as possible. The same goes if you’re dealing with adults who are (or believe they are) hypersensitive to hornet or yellowjacket venom.

Drawing down the numbers of the enemy is most often justified for nests in structural voids, and is highly recommended for two common scenarios. The first is when an undisturbed colony is readily finding access into living quarters, such as in my hornet example. If they’re leaking into occupied space now, how do you think they’re going to react when stressed? The second is when a void nest job has already been botched, usually by some yahoo who’s shot a pyrethrum-based formulation into the access hole and wondered why the wasps got so upset.

THE SUCTION SYSTEM. What do you need for successful suction? The good news is that virtually any canister-type vacuum will have enough power for most jobs (I’d suggest a backpack model), and since you’re working outdoors there’s no need for the HEPA filter that is mandatory for indoor accounts. Figure 1 at left shows my 30-year-old tried and true Craftsman shop vac, which is probably overkill in most cases and a pain for ladder work. I’m glad I had it along for the hornet job, however — those bruisers are a lot more difficult to suck up than tiny yellowjackets.

What else? Well, you can never have too many extension cords when it’s essential that you reach a source of electricity to get the job done. I like the ones with the built-in ground fault interrupt. You’ll also need a bee suit. It’s strange how some technicians will actually admit they did a stinging insect job without one, as if it’s manly to crave pain and embarrassment. A ladder is pretty important for getting up to the level of most social wasp nests in both buildings and trees, although I suppose if the vacuum was powerful enough you could get away with multiple extension wands. I’m really not a fan of that approach, however, because you lose so much control.

And last but not least, you’ll usually need some pesticide, preferably Apicide® if it’s registered in your state and you’re dealing with a structural nest (see the August 2003 issue of PCT), and preferably a rapid-knockdown aerosol if you’re dealing with an aerial nest. The reason — and it’s a big one — is that there is absolutely no way you can eliminate all the workers in a large nest with a vacuum alone. For one thing, you don’t have the time. The longest I spend on a yellowjacket vacuum job is about 90 minutes, and as soon as I start packing up to go, some more wasps invariably return to the nest. By the time I leave the site, there’s almost always continuous activity around the entrance. These outliers represent scaredy-cats that won’t leave the nest during the disturbance, wary ones that circle around but won’t return as long as something seems wrong, and foragers that were simply out hunting the whole time.

Even if it’s an aerial nest that you bag and remove, if enough workers remain behind, they often have the ability to build a small, new nest in the same location. And if the original nest is left in place, there will be two weeks’ worth of capped (pupal) cells that emerge as adults. So clients who request a pesticide-free treatment need to understand that you cannot guarantee the colony’s stinging potential has been totally neutralized.

SUCTION SAVVY. Once you’ve got your gear, there are five principal rules for a successful suction safari. First, the technique doesn’t actually pull anybody out of the nest or the nest cavity and the whole point to what you’re doing is to upset the colony as little as possible. The most efficient way to capture the wasps is to hold the nozzle underneath their entrance and zap them out of the air. It’s always easier to nail returning foragers as they’re braking for a landing rather than the departing fliers that are catapulting out of the nest.

Second, always remember that wasps are extremely sensitive to vibration. Structural nests are usually pretty well insulated from this, but nests in vegetation can have numerous branches running through them, each one a potential transmitter of your clumsiness. The only time you want to purposely vibrate their home is toward the end of the job, to coax some of the holdouts to emerge, challenge you, and join their sisters inside the canister.

Third, anticipate how the clock will affect every aspect of your work, from scheduling and pricing to the mechanics of operating your system. In general, the amount of time you will have to spend to make a significant impact on a large yellowjacket colony (the type you usually get called for) is about one hour. This is why a compact, backpack vacuum is so handy for ladder work. No matter how strong you are, you’ll be using muscles that you had no idea were there.

Fourth, wasps depend almost entirely on imprinted visual cues to smoothly orient to their nest entrance, so don’t mess up the envelope there in any way. It’s easy to do, since the paper near the entrance is usually very loosely attached and very prone to being ripped away by the suction. Even structural colonies often apply some of this material at the spot where the insects access the void. The paper scallops or curtain is almost never part of the nest itself, just an "awning" constructed by workers that have prematurely deposited their pulp loads. Keep it intact until you’re done.

Finally, although the show you’re putting on is impressive to the client and bound to generate further word-of-mouth business, remember that wielding a vacuum in a bee suit tends to attract attention. Assuming your technique is good, there’s generally not too much danger to onlookers who keep their distance. However, at least two common species of yellowjackets release a highly effective alarm pheromone when distressed that provokes intense attack behavior. This was first discovered when researchers vacuuming a subterranean colony noticed that dozens of wasps were flying up the outflowing air stream (responding to their nestmates trapped in the vacuum cleaner) and attempting to sting the machine. The point here is that even though you may be blissfully secure in your armor, always be aware of what’s happening around you and whether some curious noncombatant has approached too close for comfort.

SUCTION WITH STYLE. Now we come to the best part, the optional piece of equipment that separates the ultra-supercool from the mere professional. Back in the 1970s, the late Dr. Roger Akre designed a simple apparatus to contain sucked-up wasps in a neat package before they entered the vacuum cleaner. The device is basically a tube formed from a clear acetate sheet rolled around three plywood disks. The front disk holds the nozzle, fitted with a screened cap that covers the opening after the job is done. The middle disk has most of its center cut out and replaced with screening, which prevents the trapped insects from being sucked into the vacuum. The third disk holds a coupling tube that attaches to the vacuum hose. Voila!

Precise dimensions of the apparatus are not critical. It needs to be large enough to hold a colony’s worth of yellowjackets or hornets without its screen getting completely covered with bodies and thus having the suction blocked (although you also have the option of using several smaller tubes for a single job). It needs to be light and compact enough to hold up easily with one hand. Another consideration is being able to fit into a portable cooler if for some reason, like Dr. Akre, you wish to keep the beasties alive. I’ve built and tested a variety of these devices over the years, and they all ended up being the same general size, with the acetate cylinder ranging from 17 to 21 inches long and 6 to 7 inches in diameter.

Now why would you use one of these things? Well, mainly because it’s just so darn slick. In the argot of a popular series of commercials: ".030-inch clear extruded cellulose acetate sheet: $25. Scrap half-inch plywood and miscellaneous scrounged materials: $12. Demonstration value to client: Priceless." The spectacle of hundreds or thousands of seething hornets or yellowjackets in a secure, hand-held package is one of those extreme images that will never be forgotten (see figure 2 at right), a powerful graphic statement of the service you have just performed. The device also makes it a lot more efficient to dispose of the critters, either by placing the tube in a freezer (the humane method I prefer) or simply leaving it out in the sun.

So go ahead, take the plunge. You know you want one. Be the first kid on your block with an Akre Tube!

All photos are © Al Greene/Nancy L. Breisch

The author gratefully acknowledges the assistance and counsel of Dr. Nancy Breisch in social wasp adventures too numerous to count. The opinions expressed herein are the views of the author and do not necessarily reflect the official policy or position of the U.S. General Services Administration.

The author is regional entomologist for the U.S. General Services Administration in Washington, D.C. He can be reached via e-mail at agreene@giemedia.com.