By Chris Helzer
Wasps are amazing. No, seriously, they’re startlingly cool. To begin with, there are more than 100,000 wasp species that have been cataloged by science and many more that haven’t. Among all those species, there is incredible variation in size, shape, lifestyle and aggression toward humans. Spoiler alert: Only a tiny percentage of wasps pose any threat to us at all. Categorizing all wasps as aggressive, winged canisters of pain is like categorizing all Husker football fans as irrational optimists who always think “this will be the year!” OK, maybe that’s not the best analogy.
Most of us are so obsessed with the pointy parts of wasps that we know very little else about them. As an example, did you know that adult wasps feed only on sweet liquids like nectar? I’ll bet you didn’t. That doesn’t sound very evil, does it?
Next, let’s address the big topic on everyone’s mind. Yes, a few wasp species determinedly defend their nests and will sting you if you get too close. In addition, they don’t have barbed stingers like honey bees do, so they can sting you repeatedly. They take their nest defense very seriously.
There are two great ways to avoid being stung. First, stay away from the nests of paper wasps, hornets, yellowjackets and any other social wasps (more about them later). Second, only females have stingers, so a big proportion of wasps are completely harmless. As long as you can tell male wasps from females, you’ll know which ones to avoid. To differentiate between males and females, just count the number of antennae segments. Females have 12, and males have 13. Easy peasy.
Types of Wasps
Now that we’ve solved that problem, let’s dive into the crazy diversity of wasps and their fascinating lives. First, wasps can generally be categorized as being either parasitoid wasps or stinging wasps. Parasitoid wasps don’t have nests. Instead, females lay eggs directly on or in their prey. They have a long ovipositor protruding from their rear end, through which they can both inject venom and lay an egg. Wasps inject their prey/host with venom first to either temporarily subdue it or completely paralyze it. Then they deposit an egg, which soon hatches into a larva and feeds on the host. In order to keep the host alive long enough to get what it needs, larvae often feed first on the internal fluids, followed by the tissues, and then finally the vital organs. Aren’t you glad parasitoid wasps only use insects and spiders as hosts?
Unlike parasitoid wasps, stinging wasps actively hunt and capture prey and (most) take it to their nest to feed to their larvae. Within the stinging wasp group, there are both social and solitary species. Social wasps live in colonies, similar to ants and some bees, and split up tasks like egg-laying, foraging, feeding babies and defending the nest. Social wasps generally don’t use their stingers on prey. Instead, they usually kill their prey by chewing it up, either immediately or upon returning to the nest. Then, they feed that pre-masticated goo to their larvae.
While social wasps may not sting their prey, they’ll readily sting anyone or anything that appears to threaten their nest. If you’ve ever been attacked by a wasp, it was almost certainly a female social wasp defending her colony. To be fair, protecting one’s family is something we can all relate to. It’s just that it hurts so much when paper wasps, hornets and yellowjackets sting us — easy to see why they’re so vilified. On the flip side, those species are often used as mascots for athletic programs, a level of recognition less aggressive wasps haven’t been given. You never see team jerseys with “Mud Daubers” or “Pedestrian Mason Wasps” on the front.
Regardless, the vast majority of wasp species aren’t social and don’t aggressively defend their nests. Most live much more independent lives, earning them the name “solitary wasps.” A female solitary wasp constructs a nest, lays eggs and hunts down food for her larvae, all by herself. She has a stinger and knows how to use it, but because she is the only female in her “colony,” there’s usually too much risk involved in fighting. If she dies, so do her babies and any chance she has of passing along her genetics. As a result, she saves her venom for the insects or spiders she provides for her larvae.
Female solitary wasps often create nests by digging long subterranean burrows, but some species nest above ground in old wood or by building their own homes out of mud. Once they have a nest, they create a cell in which they deposit both egg and food. They then seal up the cell to protect it from enemies and weather. Once enclosed in its little chamber, the egg is left alone to hatch, feed and mature into an adult on its own.
The nests of social wasps include multiple generations of individuals living together and dividing up the labor involved in raising young. As with many social bees, like honey bees and bumble bees, a small percentage of social wasp individuals are raised by the colony to be reproductive females. Those reproductives, also known as queens, mate in the fall and store sperm in their bodies through the winter months. In the spring, they start constructing a nest and then use the saved sperm to fertilize eggs as they lay them in the nest. The first generation produced is typically all females, which take over the work of the colony, splitting into teams that specialize in either brood rearing, nest guarding or foraging for prey, water or wood pulp. Males come along in later generations, in time to be available for their only job: mating with reproductive females before winter.
Not all wasps fit neatly into the solitary or social nesting categories. Some, called subsocial nesters, follow the same approach as solitary nesters except that the mother will return to her eggs periodically to check on their feeding. If needed, she’ll go out and find more food for them. Subsocial nesters provide more interaction and care than solitary wasps, but still don’t live long enough to see their kids mature into adults.
As mentioned earlier, parasitoids don’t need nests because they are laying eggs right on their hosts. That saves a lot of time, but doesn’t do much to protect their larvae, which are feeding inside an immobile insect or spider that’s lying out in the open. There’s a pretty good chance a predator or scavenger will come pick up that helpless creature and eat both it and the parasitoid larva within.
You may have noticed that I’m using a lot of words like “often,” “generally” and “most” as I describe wasps and their life histories. That’s because when you’re talking about more than 100,000 species, there are exceptions to pretty much every rule.
Cuckoo wasps, for example, are pretty exceptional. These wasps don’t make their own nests or hunt their own prey. Instead, they lay their eggs in the nests of other wasps or on another wasp’s prey when it is left unattended, sometimes while the wasp is building a nest to put it in. Also known as cleptoparasites, cuckoo wasp larvae either consume the host larva as it develops or they eat the host’s food supply. Either way, the result is bad for the host.
Some cuckoo wasps will watch their host species and try to find the right time to swoop in and lay their egg in an untended nest or prey item. A few cuckoo wasp species parasitize the nests of bees instead of other wasps. Cuckoo wasps that target social wasp species will often take over the nest of the other species, either by sneaking in or by force, and then convince the workers in that colony to raise the young of the usurper.
Wasp Habitat
Wasps have three basic needs for survival. Adults that build nests need a place to build one, abundant insects or spiders to feed to their kids, and enough food to keep themselves alive until the first two jobs are done. Healthy ecosystems can provide for all of those needs and contain a wide variety of wasp species.
Ground nesting wasps dig burrows and tend to seek out places where soil has been recently disturbed. Some nest out in the open, but others will prioritize sites concealed by vegetation or protected by overhanging rocks, etc. Digging nests can be done in multiple ways, depending upon the species. Many wasps use their forelegs to dig and have specialized spines on those legs that act like a rake or shovel to help excavate efficiently. Some use their mandibles to loosen soil in front of them and then use their legs to sweep the soil behind them. Thread-waisted wasps (Sphecidae) grab the soil with their mandibles and then vibrate their thoracic muscles in a way that creates a jackhammer-like effect. There are numerous strategies for removing excavated soil from the nest too, including bulldozing it, backwards, with a flattened plate near their rear end or carrying it between their mandibles and front legs.
Solitary, above-ground nesters construct a structure to contain their egg chambers. Building above ground provides more options for locations because they aren’t tied to particular soil textures or conditions. It also allows wasps to locate nests away from ground-based predators and other threats, a strategy also employed by birds that nest in trees. Most of these wasps use pre-existing cavities in trees, hollow stems or other similar places to construct cells for eggs with a combination of mud and plant materials. Some, though, build free-standing cavities that resemble jugs or tubes, which they can place wherever they like.
Yellowjackets and paper wasps create their large nests by making their own building materials out of plant fibers. They collect those fibers by gnawing them off dry wood or grass stems. After carrying the material to the nest, they gather water and regurgitate it onto the mass of fiber before chewing it to the right consistency for building. It is thought that secretions from the mandibles, similar to saliva, may help further strengthen the resulting “paper” that is used to construct the nests.
Food for both adult and larval wasps is tied strongly to plant diversity. Since most adults feed on flower nectar, they rely on both an abundance of flowers and a wide variety of flowering plants. Most plants only flower for a few weeks a year, but there are wasps looking for food throughout the growing season, so it takes numerous plant species to ensure a constant supply of nectar from spring through fall.
Wasps also need access to lots of invertebrates to capture and/or lay eggs in. Because many wasps are particular about the kind of prey they’re looking for, both diversity and abundance of invertebrates is important. The richness of invertebrate species is usually positively correlated with plant diversity, so landscapes with lots of plant species will provide well for the needs of both adult and larval wasps.
Not All Bad
By now, perceptive readers might have noted some similarities between wasps and bees, as well as between wasps and ants. That’s no accident, since bees and ants are actually descendants of wasps. Evolutionarily speaking, ants are just wasps that gave up flight, except when mating. Bees are basically wasps that became vegetarian, feeding their larvae pollen and nectar instead of meat. Ants with wings look like wasps, and while bees are generally tubbier than their skinny-waisted wasp cousins, some species require a microscope and considerable expertise to determine if they are one or the other. Ants and bees are fascinating in their own right, but there are only 12,000 ant species in the world and about 20,000 bee species. Whoop-de-doo.
Wasps tend to have a bad reputation among most people, but if you’ve read this whole article, you’re not most people, are you? You’re now in possession of an array of captivating facts that will make you the envy of all your friends. Knowledge comes with responsibility, however. Your job is now to bolster the image of wasps among all those you come in contact with. At a minimum, you can reassure people that most wasps aren’t out to get them and rave about the incredible diversity of wasps and their value as both pollinators and regulators of insect and spider populations. Based on personal experience, I’d be a little more circumspect about sharing the bits about wasps paralyzing small creatures and feeding them to their babies, but I guess that depends on your audience.