Ask The Entomologist

The time to start trapping wasps is now.

While winter isn’t quite done with us yet, we’ve had a good period of warmth recently. Wasps, as well as bears, are waking from their winter hibernation. I’ve seen a few queen paper wasps scouting for new nesting sites.

With this in mind, if you want to control wasps in or around your property, the time to start is now. If you can catch and kill the wasp version of a queen, you’ll stop her whole colony from bothering you the rest of the summer.

(A wasp queen is called a “gyne”, which means “woman” in ancient Greek. Gynes are quite large – perhaps twice the size of a standard wasp. Gynes are the wasps most likely to not die in hibernation.)

While most paper wasps will try to hibernate through the winter (the reason we see them moving indoors in fall), most are unsuccessful. Most wasp queens have to start anew in spring, building their new colonies (and sometimes their nests) from scratch.

Raising kids can be hard work, as any parent can tell you. It’s no different for wasps. As gynes start building their new nest, and laying their first eggs of the season, they spend most of their time looking for food for their young.

(A gyne’s first eight or so children are called “haplogynes” meaning “half-women” – these are about half as large again as a standard wasp. These haplogynes take over caring for their little siblings, leaving the gyne free to lay more eggs and expand the nest.)

Developing wasp larvae, just like developing human children, need diets rich in protein to grow and build muscle tissue. As such, a gyne caring for her first batch of larvae will spend much of her time looking for meat to feed them with. Later in the year, wasp larvae will often be fed caterpillars. But early on, carrion forms much of the available meat.

If you want to control your wasp problem before it starts, consider setting a wasp trap and baiting it with a bit of leftover meat and letting it spoil. If you manage to catch and kill a gyne, or her crew of haplogynes, you’ll have won a war before giving it a chance to start.

(Bear in mind, we do live in an area with bears, who are also beginning to leave hibernation. Be bear aware, and cautious in your use of meat to bait wasp traps.)

Ask The Entomologist

Ichneumonid wasps, imposing allies

Last Thursday I saw this lovely Ichneumonid wasp (pronounced ICK-new-mon-id, from Greek “Ιχνευμων” which means “Tracker”). Most of the time I see Ichneumonids, they’re on the sides of trees, ovipositing (laying eggs) in boring insect larvae. This one’s behavior was very odd indeed.

An Ichneumonid wasp, Pimpla pedalis, oviposits into a newly split piece of Douglas Fir.

As you can see, this particular Ichneumonid wasp was laying her eggs inside a freshly split piece of Douglas Fir … or rather, inside a boring insect inside the Douglas Fir. Curious to see what insect she was laying her eggs inside, I peeled away layer after thin layer of wood …

Uncovering the beetle grub (at left, mid-height) the wasp laid her eggs in.

… And after an inch and a half of wood was removed, exposed a boring beetle grub. This is a Jewel Beetle grub, a member of family Buprestidae. These beetles can be lumber pests, though they’re unlikely to damage treated wood. While none of our Montanan Jewel Beetles are quite as bad, the Emerald Ash Borer has been devastating to ash trees throughout eastern North America.

There it is, a Buprestid beetle grub, just to the left of the burrow it gnawed in the wood.

I have very fond childhood memories of Giant Ichneumonid wasps. Most Sundays, my family would go to the arboretum of South Dakota State University’s then-public gardens. Among my favorite things there were some large multi-trunked cedars, which, in autumn, attracted some very large wasps. Presumably, the cedars also had very large wood-boring larvae that the Ichneumonids were parasitizing. Despite being a typical small human, making noise, climbing trees, and being generally bothersome, the Ichneumonid wasps never showed any sign of interest in me.

While their large stingers and stinger sheaths look quite formidable, Ichneumonid wasps very rarely sting mammals or other large animals. Unlike typical colony-living wasps and bees, Ichneumonid stingers are almost exclusively used for laying eggs inside of host insects. Eventually the eggs hatch, and the baby wasps eat the host insect from the inside out. Parasites that always kill their hosts are called parasitoids (think of the Xenomorphs from the Alien movies).

Fortunately for us, in addition to not stinging us or our pets, Ichneumonid wasps are also great at controlling garden pests. They take out a variety of garden pests (tomato hornworms, cabbage worms, etc.) as well as lumber pests (long-horned beetles, jewel beetles, bark beetles, etc.).

All in all, they’re neighbors I’m quite glad to have.

Ask The Entomologist

Wasp control

I’d wanted to talk about how to read wasp body language this week, but that’ll be postponed. I couldn’t persuade any individuals to do threat displays this week – all live wasps were well-mannered, despite extreme invasion of their personal space.

Most of the wasps I’ve seen around Trego are Polistes paper wasps. We have two main species here – the invasive European Paper Wasp (Polistes dominula) and the native Golden Paper Wasp (Polistes aurifer). In our area, Golden Paper Wasps peak in July, while the European Paper Wasps peak in August. While both are still around, I’ve been seeing far more European Paper Wasps lately.

The European Paper Wasp is rather special, in that it doesn’t mind reusing old nests from last year and making them bigger. Because of this, they often reach a larger colony size faster than their native wasp competitors can. As such, these are likely to be most of the problem paper wasp nests you come across.

The best bait for trapping wasps will vary by season. My neighbors have been having great success baiting their wasp traps with scallop and chicken… this means that the wasps that they are catching are from nests with many developing wasps!

A meat-baited trap full of European Paper Wasps – this indicates that there are nearby nests full of wasp larvae.

At this, another friend present asked me why folks these days trapped wasps with meat – he remembered his grandmother having lots of success baiting wasps with beer. The answer is that it depends on the season, and what part of their life cycle the wasps are in…

Early on, a wasp nest is focused on growing: laying eggs and raising larvae to adulthood. Little humans need healthy food, protein to turn into muscle tissue. The same is true of young insects: adult wasps prefer to feed their larvae with protein-rich foods (any meat – caterpillars or dead deer, it makes no difference). If you’re seeing wasp nests with lots of brood cells by your home, consider putting a bit of meat, especially spoiling meat, in your wasp trap!

A nest of the invasive European Paper Wasp – note the cells capped with silk, these contain developing wasps.

Adult insects, however, aren’t going to build any more muscle than they already have. We mammals can continue to develop our musculature throughout adulthood. Insects only get bigger by molting, and almost all adult insects do not molt.

Though they don’t grow, most adult insects do spend a lot of time flying. Flying is very energetically expensive (it’s why hummingbirds are such sugar junkies). Likewise, adult wasps prefer to eat high energy, sugary foods. If you’re trying to trap wasps later in the season, when they’re reproducing less, you’ll have better success baiting them in with sugar solutions, juice, or alcohol.

Here’s good instructions for making a wasp trap – bait it however you’d like.
As always, be aware of your local wildlife when setting up insect traps! If you’ve got a bear in the vicinity, it’s probably best to hold off on trapping for a while. They’re at least as fond of meat and booze as the wasps are…

Next week: Wasp body language: how to tell if they’re aggressive.
(for real this time – none were aggressive towards me this week, so no useful photos).

Ask The Entomologist

Wasps… they’re not always out to get us.

What says midsummer better than unexpected wasp nests? Buzzing uncomfortably overhead, nests full to bursting with developing young. Dreadful things, right?

What would you say if I told you that aggressive wasps (think of your stereotypical Bald Faced Hornets) aren’t the only kind out there? Even within a single species, there are a wide variety of levels of aggression.

If a wasp is going to be aggressive to protect her nest, full of her offspring and her sisters’ offspring, she really has to go all out. If a wasp doesn’t give her all when driving potential threats away, chances are that the nest will have to repel more attacks, and the nest will be more likely to be detected by more dangerous predators! Predators who will attack and destroy that nest, despite angry wasps and stings. Both mammalian predators (bears, humans, etc.) and insect predators (especially ants!) are more likely to attack nests that reveal themselves by being aggressive.

While bears are stereotyped as being very fond of bees’ honey, they also relish eating the “brood”. “Brood” are the developing larvae or pupae that will grow up to become wasps or bees. While you can only get honey from some sorts of bees… you can get delicious brood from any active bee or wasp nest!
Think of snacking on sugary fresh fruit… now think of eating a ham sandwich… Which one makes you feel more full? Bears, especially young ones, love protein-rich young insects.

There’s another strategy for survival. What if the wasp was sneaky, stealthy, and conflict-avoidant instead of being crazy aggressive? It turns out that this is a valid strategy for survival, too. Think about it – if nobody knows the wasps are there, nobody will be trying to eat their brood!

Different colonies of the same species of wasps often vary widely in how aggressive they are! Not all paper wasp nests are terrible… I’ve certainly met some aggressive ones when cleaning roof gutters and peeling off siding, but I’ve met others of the same species who wanted nothing more than to escape notice! Look at this nest, tucked below the hinge of our vehicle’s front passenger door:

These wasps had no interest in attacking us – I got within 3 inches of them with my camera, and none made threat displays. I only noticed them because I saw the same species of wasp flying outside of the vehicle as we started it up… I saw these wasps several times in a row, despite it being parked at different places… including some where this particular paper wasp isn’t common. The wasps were being sneaky – they’d found a warm place to rear their young, inside a protected shell that ants and bears alike would be unlikely to spot them in. And it worked out well for them… until I saw them and decided that I didn’t want them meeting the dog.

Next week: How to read a wasp’s body language. Apologies, folks, wasp control instead.