More about wasps. …

First of all, though, an apology. I expected to be able to get back to you a little sooner.

As I was saying, paper wasps are the most common problem directly around dwellings. They are not, in general, prone to sting, even fairly close to the nest, if they do not feel threatened. For this reason, it’s best not to threaten them unless you mean to remove the whole lot of them. To this end, here are a few ways to seem less threatening:

1. Avoid making any major changes near (within 8 feet of) the nests. The stinging wasps are all highly visually oriented, and they map the area near the nest. If there are visible changes, the wasps returning from foraging will become much more agitated and aggressive. They are especially attuned to straight lines and geometric forms in contrast-y colors. A couple rake or shovel handles against a wall that were not there before can be enough to cause difficulties, especially if they see you as an enemy.
2. It’s best not to swat at them or attack them with any implement unless you’re determined to finish off the nest and kill all the inhabitants. Even if they cause some distress, the safest way to get past even a fairly large number of paper wasp nests is to walk past at a measured rate. The more wasp you actually disturb or injure in your passing, the greater the likelihood that you will be stung in the future. This is because they almost certainly recognize you by this point in the season, if they are near any area you frequent. They have fairly good visual acuity, excellent scent receptors, and a reasonably accurate memory.
3. By this time of year, a fairly large number of paper wasps are male. Male wasps are notably more aggressive, but they cannot sting (it is hard to tell them apart from the females). If the wasps are flying at you very aggressively, chances are they are male — note that this is not true of yellowjackets; more on them in a minute.
4. Vibration is the threat they will respond to the fastest. Try to avoid slamming doors or windows, or otherwise bumping structures they have built nests on, until you are ready to eliminate the nests. This will reduce stings.

I have worked with paper wasps a lot. Their sting is the most painful of the wasps I have been stung by, but they are much more docile than the next bunch: yellowjackets and hornets.

Yellowjackets are medium-sized (no more than an inch, usually) wasps that build fairly large colonies of paper cells underground, either in old mouse or ground squirrel burrows, or by taking over other wasps’ or bees’ nests. They enlarge the burrows by removing the soil in their jaws until they can become quite large. In your area the largest colonies will likely number 2000–3000 wasps. Sometimes they are found in utility crawlspaces as well. Early in the season they tend not to be aggressive, because they are expending most of their energy feeding their young with either captured prey (other insects or spiders) or scavenged meat. The adults subsist on nectar from flowers, so they can be a pest near hummingbird feeders or near sweetened drinks. As the summer wears on the adults will range farther and become more aggressive on their own. Most yellowjacket stings happen in August and September for this reason.

The safest way to be rid of them is with water-filled traps, which you can usually find at your local feed store (Tractor Supply has them). The traps are very effective if you have the right bait. Some species will only be attracted to certain scents; others will be attracted to any smell of meat (hotdogs are good bait for them). If you feel a need to eradicate a nest, that is a job for a professional. Chances are, even if you can precisely locate the nest, there will be too many wasps there for you to deal with safely on your own. That said, if you feel a need to find a nest that has been particularly bad, let me know and I can advise. The more traps, the better.

Hornets, in your area, are not the true European Hornet (found in the Northeast where it was imported to help combat Gypsy moths), but the smaller (close relative of the yellowjacket) so called Bald-Faced Hornet. These make football-shaped paper nests in trees or under eaves. They are not dangerous if there is no nest near your home: their interest in you is negligible. They actually prey on the smaller yellowjackets, and so can be beneficial. They rarely go after any human foods, but will defend their hunting territory if swatted at. The safest way to deal with them if they are present in small numbers (hunting, or chewing raw wood — which they use for their nests) is to leave them alone. They fly very well and can not only sting, but have been known to spray venom at the eyes of people they see as a threat. If there is a nest near you, the most effective way to remove them is to puncture the outer envelope of the nest by throwing a rock at it or shooting it with a pellet gun, then spraying it with water. The paper of the nest disintegrates rapidly. They can be removed with poison sprays, but they are very resilient and aggressive. When using these sprays you can expect a few stings, and it will take several days for all the hornets to die off. If there is a large nest (basketball size or bigger), it’s best to call a professional, no matter how brave you are.

Finally, the only other wasp likely to be a problem near people is the Mud Dauber wasp. They construct tubes of mud which they stock with prey for their young to consume (spiders, usually) which they have paralyzed by stinging them. They are usually quite docile (again, the males are often more aggressive), but have a very unpleasant sting if they do sting. They do not build many nests, generally, in areas where people are in and out a lot, so they are often more of a problem in sheds and outbuildings. Even then, they will rarely sting unless handled or swatted at. The nests can be removed with water spray or by scraping. If they are persistently building nests in an inconvenient area, a treatment with the same spray used for paper wasps will prevent any more nest building.

A few general notes about these wasps:

They are all susceptible to cold, and to wet. As summers get hotter and drier more of them will be able to thrive, even in areas where, due to climate, they may not have been pests in previous years (or at least not as bad). The best way to minimize the impact on your home is to deal with them aggressively early in the season. At the very beginning of warm weather, there are usually a few queens of various species looking for locations for nests. Each one of those wasps eliminated can cut down the number of wasps later in the summer by hundreds. I am not advocating the wholesale slaughter or poisoning of wasps. They are, in fact, highly beneficial pollinators and predators on other pest species. but if they are close to your home they can be very difficult to deal with. If you’re in the Denver or Colorado Springs areas, there may be people who will come harvest your wasps for anti-venom research. Otherwise it may be possible to have them removed by professional pest control companies, or possibly by a local bee-keeper (who, in any case, is more likely to understand the dangers and have some specialized equipment).

So, for next year, if you know the wasps are coming to your house, remove the nests early (when they’re no larger than a quarter, if possible — they rarely ever sting at that stage, unless captured bare-handed), and be vigilant. Inspect all the possible nest sites once a week or so, and remove them immediately if they are found.

I hope some of this helps, Anna and Jack. I will be happy to give more advice about them if you have specific questions (if you can get a picture of a nest or wasps that is sometimes helpful). Feel free to PM me if you need specific advice and don’t care to have it shared here; I don’t mind everybody being in my wasp business, so that’s up to you.

Also, for what it’s worth, I will happily answer any other insect questions I can (I do wasps, lacewings, some flies, and aquatics (stoneflies, mayflies, caddisflies, and dobsonflies), mostly). Good luck and best wishes.