Weekend Cleanup Part 2: All About Yellowjackets

Note: Yes I’m late. I said I’d get this post up Wednesday. Then I said over the long weekend. But I didn’t get it up till now. Here’s the deal:

1) The post required some research. Seriously, all my posts do. It’s not like I just throw this crap together*, you know…

*Expect for my “filler” posts, which are wonderfully research-free and totally stream-of-consciousness**.

**Kind of like this note.

2) No one reads blogs over the weekend anyway. Why waste a great post like this- oh, and yes it’s great alright*- on a weekend?

*Especially my new Expand-O-Graphic. Man it is so awesome you are totally going to pee your pants when you see it!

3) OK the real reason. I blew off everything this past long weekend. We (Watcher-Family-Unit) went down to St. George for the holiday. And I just wanted to hang out with AW and the Trifecta. And it was great.

The Post Already

Like every North American suburban homeowner, I’ve had my run-ins with Yellowjackets, including many summer outdoor meals that were scuttled due to their persistent interference. And like so many homeowners, we turned to traps. When I spotted the 2 dead yellowjackets on the garage windowsill (pic left) I belatedly remembered that our 2 traps from the summer were still hanging in the back yard, and given that it was almost Thanksgiving, I really ought to clean them out.

Tangent: You’re not a real man until you can regularly kill yellowjackets with your bare hand. It’s not as hard as it sounds. They just have to land on a hard surface for a second so you can swat them. They key is not to crush them, but just lightly stun them so they fall to the ground where you can follow up with a vigorous stomp*. Remember- the stinger always points down, so if you hit it quick from the back it can’t sting you.

*If it falls to soft earth you may have to augment your stomp with a thorough and heartfelt back-and-forth grind. Obviously this doesn’t work if you’re barefooted.

All About Yellowjackets

But first, what is a yellowjacket?

Yellowjackets are one of about a dozen different wasp species belonging to the genus Vespula. Oh wait, I guess I should first explain what a wasp is…

OK, a wasp is a type of hymenopteran. Hymenoptera is a huge and very successful order of insects that includes lots of things we’ve blogged about including ants, bees and tarantula hawks. There are thousands and thousands of species, generally sharing many anatomical features including well-developed mandibles, ovipositors, apposition compound eyes* and 2 pairs of wings which lock together via a set of specialized bristles, called hamuli.

*Which I explained in this post. And actually I should put in a qualifier; I know all Apocrita (Ants, Bees, Wasps) have apposition compound eyes, but was unable to confirm that Symphata (sawflies, horntails) also do in time for this post.

Probably the 2 most interesting things about hymenopterans are this: First, sex is determined by number of chromosomes, as described more fully in this post. Females are chromosomally diploid, with 2 sets of chromosomes, one from her mother, one from her father, just like us. But males are chromosomally haploid, with just a single set of chromosomes, which they get from their mother. Hymenopteran males have no fathers.

Second, the order Hymenoptera includes- with one notable exception*- all of the world’s social** insects- namely ants, bees and wasps. However, not all hymenopterans are social; many that we’ve looked at- like tarantula hawks and orchard mason bees- are solitary. Hymenopterans have been around since the Triassic period, but social Hymenopterans didn’t appear till the Cretaceous.

*Termites, which I later covered in this post. Man, by the end of Part 1, it was like I had a post for everything.

**The term entomologists seem to usually use now is “eusocial.” The “eu” part means “good” and it’s meant to describe specifically social living for a common reproductive system, as in a beehive with a queen, etc.

Hymenoptera is divided into 2 sub-orders. The first, Symphyta, includes stuff like Sawflies and Horntails and a bunch of things we’ve never covered but maybe I’ll get around to someday. These guys are thought to be the more “primitive” hymenopterans, closer to the ancestral form.

The second, Apocrita, includes ants, bees and wasps- all the social hymenopterans- and is characterized by the classic “wasp-waist”, or petiole.

A wasp is any species of Aprocrita that is not a bee or an ant. But that doesn’t mean that all wasps are more closely-related to each other than a given wasp is to bees or ants. In other words, “wasps” per se are not a monophyletic group*. Below is one of my Very Crude Phylogeny-Graphics to help you understand how all these wasp/bee/ant critters are related.

*I explained what a monophyletic group is in this post.

Like all my Phylogeny-Graphics it looks kind of complicated and dull, but as you go through the rest of the post you can bounce back up whenever you get lost to remind yourself of what’s what. Got it?

Tangent: “WASP” is of course also an acronym for White Anglo-Saxon Protestant, which I heard used often when I was growing up, but probably haven’t heard more than once or twice during the last decade. Maybe it’s a regional thing. Or maybe- hopefully- people just don’t care about that stuff as much anymore.

Nested Tangent: My father’s side of the family are WASPs. Once in the late 1980’s my sister- let’s call her Elizabeth- and I were having dinner with a slightly-older paternal-side female cousin. The cousin was bemoaning her single status and how hard it was to “find a nice guy.” We asked what kind of guy she was hoping to meet, whereupon she answered- completely seriously, “Oh, he doesn’t have to be perfect… just, you know, white, Ivy League-educated, Anglo-Saxon, Episcopalian…”*

*Yes, she really said that. To my sister and me (who were neither Anglo-Saxon nor even Protestant.) And yes, she’s still single.

Anyway, the guy who cooked up the acronym was a University of Pennsylvania Professor named E. Digby Baltzell, who was widely regarded as some big-shot intellectual for his book The Protestant Establishment. My senior year at Penn I took his sociology class as an elective.* Digby had a (rather odd) policy that if you got an A on his first exam you didn’t have to take any more exams, and what’s more, he took you to lunch at the faculty club.

*Because I was a EE major about to start job-hunting and desperately needed to boost my GPA, and yes, Soc classes are easy…

Appealing as this policy did to my innate sense of laziness, I studied my ass off and aced the exam. Digby took several of us to lunch, which I remember being rather boring, the talk focusing mostly on collegiate sports. I mentally checked out, smiled and ate eggs benedict.

OK so yeah anyway yellowjackets are a small genus of wasps. There are about a dozen different species, strung mainly across the Northern hemisphere, but also introduced to places like Australia and New Zealand. And on the surface of things, they’re sort of like bees. They have queens and drones and workers with stingers and live in hives. But where bees run around collecting nectar* and pollen to make honey, yellowjackets are hunters, targeting caterpillars, flies, spiders and hemipterans (like box elder bugs.) Basically they’re carnivorous bees.

*Yellowjackets and many other wasps will also visit flowers for nectar, but just to consume directly; they don’t make honey.

And they’re adaptable and willing to try and/or raid new food sources. They’ll often try to invade bee hives and steal honey*. A large, healthy hive can usually fight them off, but if the hive is weakened by illness or Colony Collapse Disorder, they can be overrun.

*Lest you feel too sorry for the poor bees, you should know that bees of different hives also raid each other for honey.

From our standpoint, this adaptability has a downside: many yellowjacket species* are persistent and aggressive scavengers, frequenting cook-outs, picnics and garbage cans with annoying predictability.

*Primarily the V. vulgaris group, highlighted in the Phylogeny-Graphic above

Oh, and there’s another difference between yellowjackets and bees: yellowjacket stingers aren’t barbed. This makes sense an insect that hunts for a living; if her stinger got torn out on the first sting, she’d never live to eat a meal. But for us humans it means that unfortunately, yellowjackets can sting repeatedly. And they’re much likelier to sting*.

*Which makes sense, given that they get to sting more than once…

The lifecycle of yellowjackets is a bit more somber than that of bees. While bees huddle together and consume stored honey reserves to survive the winter, yellowjackets just die. The workers die, the drones die, the founding queen of the colony dies. The only yellowjackets who survive the winter are impregnated “new” queens.

Come Spring, the pregnant new queen emerges and seeks out a nest site, where she starts to construct a nest out of paper that she creates out of chewed plant matter mixed with saliva. She lays eggs in the nest, and when larvae hatch, feeds them with food- hunted or scavenged- which she brings back to the nest.

The first generation are all workers. Yellowjacket queens and workers are similar in form, though the queens are about 30% - 50% larger, and have slightly different abdominal markings, as we’ll see in a moment. After Generation One is raised, they take over the nest-provisioning and young-rearing duties from the queen, who then focuses her efforts on laying eggs. More generations of workers are produced, but as the summer progresses, the queen switches to laying eggs for reproductives- drones and queens. In some species the switch is dramatic and complete, while in others it’s more of a gradual mix and changeover. Later in the summer the reproductives go out on mating flights, and as Fall settles in the newly-impregnated queens hunker down for the winter and the cycle starts anew. Every winter is the end of the world for a yellowjacket colony.

Interestingly there’s some evidence that food preference changes throughout the summer. Early on, when workers are being reared, yellowjackets seem to prefer fresher food, and meat. Later in the summer they seem partial to decomposing food. (So it may well be that they’ll raid your cookouts more often in the early summer, and garbage cans later on.)

Our trap had probably ~40 yellowjackets inside. Curious as I was to make a species ID, I opened the trap and spilled the contents out onto a large plate.

The most common yellowjacket in the Western US is the Western Yellowjacket, Vespula pensylvanica. It’s an aggressive, annoying scavenger, and loves human garbage. Another garbage-loving yellowjacket, common to both North America and Europe, is the Common Yellowjacket, V. vulgaris. I expected that our trap would contain one or both of these 2 species, or possibly the Forest Yellowjacket, V. acadica, which is also common in the Western US, but only hunts live prey, and so isn’t much of a nuisance.

Side Note: in the Eastern US the Common Yellowjacket is still common as are a couple of other species, including the Eastern Yellowjacket, V. maculifrons, and the German Yellowjacket, V. germanica, which is native to the old world but has been introduced to t he US. Both are pest/scavenger species, and interestingly, the German Yellowjacket seems to be in the process of displacing the Eastern.

So how do you tell different yellowjacket species apart, anyhow? By the markings on their abdomens. Each species has distinctive black-on-yellow marking patterns for its queens, drones and workers. Here are examples I pulled from this extremely helpful Canadian site.*

*I love Canada.

But when I examined the yellowjackets in the trap, I failed to make a match. So I uploaded a shot to my friends over at bugguide.net and had an ID within 20 minutes.* And it turns out that my yellowjackets weren’t quite so ordinary after all. They were Prairie Yellowjackets, V. atropilosa, a species native to the US, but which- according to the good folks at bugguide.net- shows up much less frequently in traps. Prairie Yellowjackets often nest near yards and golf courses**.

*Those guys are awesome. I love that site.

**We live 2 blocks from one.

Their nests are small, with a maximum of ~500 workers, or only about 10-20% the size of a Common or Western Yellowjacket nest.

Most important to humans though, V. atropilosa hunts only live prey; it’s not supposed to be a scavenger, and generally doesn’t bother humans. This last bit is a bit of a head-scratcher for me; we were absolutely hassled during outside meals this past summer, but of the ½ dozen or so carcasses I checked from the trap, all were V. atropilosa. Hmm…

Side Note: None of these species however was what I was really hoping to find. No, what I really wanted was to find a Cuckoo Yellowjacket, V. asutriaca. If I had, it would’ve been a queen (or a drone) because there are no V. austriaca workers.

Cuckoo YellowJackets are social parasites. The queens invade the nests of other species- most commonly Forest Yellowjackets- and systematically hunt down and kill any queens. They then take over the colony, directing the workers, who then (unknowingly?) rear the Cuckoo Queen’s eggs, which are all queens and drones, and which eventually take flight to mate, then seek out, invade and subvert other Yellowjacket nests. It’s like something out of a sci-fi horror flick!

The "take-over", specifically the killing of the resident queens, is followed by a period of apparently aggressive bullying behavior by the new austriaca queen, including forced trophallaxis. Trophallaxis, common to most (All?) social hymenopterans is an exchange of regurgitated foodstuffs. With yellowjackets it commonly occurs between adults, who regurgitate pre-chewed meat, and larvae, who secrete a sugary substance in return. It's thought that the new queen asserts control through some combination of force, threat and pheromones.

Nested Side Note: The need for such "bullying" makes me wonder a) how thoroughly the workers are "fooled", if at all, by the queen-switch, and b) are workers always bullied- in “normal”, non-parasitized colonies- to some extent into compliance? Meaning, we sort of assume that workers in wasp, bee and ant colonies do what they do because they "want*" to do it, but is that the case, or are they actively bullied/threatened into doing what they do?

*When I say "want" here, I'm not suggesting that a wasp or bee sits there and thinks about it; I mean that the wasp or bee naturally does the thing, without prompting, force, threat or direction.

This socially parasitic takeover schtick BTW, is not unique. There are other (non-yellowjacket) wasps and a number of ant species that are socially parasitic as well.

So the contents of my trap turned out a bit more interesting than I’d expected. But my thoughts returned to the garage, and the 2 dead yellowjackets that had started this whole little project. Clearly they were different from the Prairie Yellowjackets, but I was unable to make an ID. Again I turned to bugguide.net and again I quickly had my answer.

It turns out I couldn’t make the ID because- after all this- they’re not yellowjackets. They’re Paper Wasps, specifically Polistes dominula, the European Paper Wasp.

Paper wasps, like yellowjackets (who are sometimes lumped in with them) construct paper nests out of chewed up plant matter mixed with saliva. But a true paper wasp nest always conforms to a specific design with open combs and a small stalk, called the petiole (no, not a typo; it’s the same word as for the “waist” connecting the hymenopteran thorax and abdomen.) They usually build nests above ground, in places like eaves. Yellowjackets more often build below ground, or in rotting stumps, logs, compost heaps, etc. A yellowjacket nest usually has a single or few openings; a paper wasp nest*, with its open cells, has many openings.

*The nest in these pics was also a result of weekend cleanup- located inside the hollow base of the patio-table umbrella.

Native paper wasps don’t look too much like yellowjackets; the coloration is different, and the rear legs hang down while in flight. But the P. dominula does look like a yellowjacket, with its black-on-yellow abdomen. The giveaway is the antennae: Euro-Paper Wasp’s are orange, yellowjacket’s are black. In general paper wasps are far less aggressive than yellowjackets, with one exception. That’s right- the European Paper Wasp.

Probably the most interesting thing about the Euro-Paper Wasp is that it is common and widespread clear across the US, yet didn’t exist here when I was born. It’s not clear exactly when it was introduced- sometime between 1968 and 1981 for sure. The likeliest scenario appears to have been two separate introductions: the first in the late 1960’s in New Jersey, and the second in the late 1970’s, probably in or around Cambridge or Somerville Massachusetts. Think about that second introduction for a second: There’s a 50/50 chance that the 2 Euro-Paper Wasps I found in the garage last weekend were the ~30X great-grandchildren of a queen introduced to North America when I was 13 or 14 years old, within 10 miles of where I was at the time*. Wow.

*Awesome Wife would’ve been about 7 at the time of the New Jersey introduction, living in- that’s right- New Jersey. It’s like these things tracked us down across the continent.

Long before P. dominula showed up, there were nearly 2 dozen native species of paper wasp in North America, the most common of which is Polistes fuscatus (pic right, not mine). P. dominula, in the course of its rapid expansion, appears to be displacing and replacing the far less aggressive native species, so keep an eye out for it; it may not be around for your grandchildren.

So. All those cool bugs and stories in just a couple hours of weekend “clean-up” work. We were down in St. George this weekend, and had a wonderful time, but part of me couldn’t wait to get back home. Back to my garage.

Note: Special thanks for “Vespula vulgaris”* over at bugguide.net for the V. atropilosa and P. dominula IDs. I’m always extremely grateful for the effort and consideration shown by topical specialists who take the time to help out motivated laypersons.

*His handle. Don’t know his real name. Why am I saying “his”? Don’t know that either. Only he comments like a man. Specifically, he said, “Nah” in a comment. Only guys say “Nah”, right? OK, starting tangent in footnote to thank-you-note. Must stop now.