How Wasps Work


Both an ancient rival and ancestor of the honeybee, wasps may not produce honey, but they do help pollinate plants and eliminate insects that feed on crops. See more insect pictures.
©iStockphoto/James Benet

You wake up inside a hexagonal chamber. There's a burning hole in your side, and no matter how hard you try, you can't move a finger. Paralyzed, you watch in horror as the pale, bulbous creature at the other end of the chamber begins to crawl toward you with hungry, snapping jaws …

Sure, you might be the unfortunate victim in the latest sci-fi horror flick, but more than likely -- on this planet, anyway -- you're one of the millions of spiders and insects locked away by wasps each year to feed their growing broods of larvae.

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This parasitic nursery arrangement is rather common with most species of wasp. It's almost as infamous as the stings they pack to protect their nests -- both have helped to give wasps a somewhat vicious reputation.

Honeybees evolved away from their prehistoric wasp ancestors to pursue a quiet life of making honey to feed the family at home. Though most modern adult wasps' diets never evolved beyond eating pollen, they do bring home paralyzed victims for the kids to devour. Some even jumped at the opportunity to steal from bees and fellow wasps. Millions of years later, honeybees have achieved full-blown "cute" status and are the subjects of countless picture books, cartoons and children's toys. Wasps, on the other hand, are lucky to land a gig as a sports mascot.

No matter how uncultured they may seem in comparison to bees, wasps lead complex lives. Despite the fact you'll never find anything called "wasp honey" at the local grocery store, wasps perform a vital service by helping to pollinate the world's plant life and eliminate various six- and eight-legged pests.

In this article, we'll examine the fascinating anatomy, lifestyle and social graces of one of the smallest creatures ever to chase grown men and women away from a picnic.

Wasp Anatomy and Diet

Wasp anatomy
Wasp anatomy
How Stuff Works

There are more than 20,000 species of wasps crawling and flying all over the Earth, so it comes as no surprise that a great deal of variety exists when it comes to their color, size, shape and lifestyle. However, a few fundamentals can be found pretty much anywhere you look.

Like all insects, wasps possess hard exoskeletons of chitin, divvied into three body segments:

  • The head boasts one pair of sensory antennae, mouthparts for biting and licking, and two kidney-shaped clusters of compound eyes and simple eyes (known as ocelli). Inside the head, a tiny brain tends to the tasks at hand. Some areas of the brain expand when certain species of wasp are confronted with difficult tasks [source: University of Washington].
  • The thorax features six spindly legs and a pair of swift, membranous wings. The legs and wings in many species provide enough strength for the wasp to fly away with a paralyzed victim in its grips.
  • The abdomen contains the majority of the wasps' organ systems and, in female wasps, a deadly stinger for self-defense and hunting.

Together, these segments create quite the little killing machine. But to understand how this body serves modern breeds of wasps, you have to imagine how it originally served them in the days before flowers.

Flowers and wasps share a mutually beneficial relationship.
ICHIRO/Taxi Japan/Getty Images

About 100 million years ago, during the Cretaceous Period, Earth was quite a different planet. It was devoid of flowering plants and occupied mostly by conifers, which depend on the wind to spread their seeds. This evergreen world crawled with insects, among which could be found ants and their winged cousins the wasps (both members of the order Hymenoptera). Everyone was fighting for food and survival.

The wasps of this age were carnivorous, preying on spiders and other insects -- many of which in turn fed on vegetation. Plant evolution eventually began to make the most of this constant insect traffic, using it like the wind to carry genetic material from plant to plant. The result was the rise of angiosperms, plants that depend on insects to spread genetic material in pollen from male plant parts, called anthers, to female plant parts, called stigmas.

Basically, these plants learned to trick insects into carrying their genetic material for them. The addition of delicious nectar and pollen only sweetened the deal for the insects, giving them specific reasons to traffic the parts of the plant where pollen was produced. Prehistoric wasps picked up on this free meal and, over time, grew largely to depend on nectar as their primary food source.

As they evolved, honeybees learned to gather pollen and bring it back for their young, but wasps never caught on to the whole honey-and-wax enterprise. So while adult wasps largely put aside their flesh-eating ways to dine out at the local flowering angiosperm, they had to continue bringing meat back for the hungry larvae at the nest -- kind of like vegan parents who bring home a pepperoni pizza for the kids.

 

This arrangement plays a major role in the life of most species of wasp and is one of the reasons these nectar-eating creatures pack such a powerful sting.

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Wasp Stingers

A modern parasitic cotesia wasp lays its eggs inside a caterpillar after giving it a paralyzing taste of its stinger. In this, the cotesia wasp behaves much like the Jurassic ancestors of all bees and wasps.
A modern parasitic cotesia wasp lays its eggs inside a caterpillar after giving it a paralyzing taste of its stinger. In this, the cotesia wasp behaves much like the Jurassic ancestors of all bees and wasps.
Albert Mans/Minden Pictures/Getty Images

Wasps are known for their stings -- if you know nothing else about them, you probably recognize which end of them to avoid. But where did they get their stingers, and what purpose do they serve?

Step back even further in time to the Jurassic Period, before bees and wasps split ways on their evolutionary paths, and you'd find that those stings can be traced to a little female egg-laying organ called an ovipositor. This is why you'll find only female wasps packing heat.

Wasp stinger
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Prehistoric parasitic wasps would use the pointy appendage to lay eggs directly onto living insects such as caterpillars -- which the hatching larvae would then consume. But why lay your eggs on a caterpillar when, with a little evolution, you can lay them directly inside your victim? So ovipositors grew sharp, sometimes saw-toothed, all to help wasps better perform this surgery. And since the chosen insect hosts tended to take offense and fight off the wasps' advances, the ovipositors also evolved to pack a venomous punch.

Some modern parasitic wasps continue this very practice, either peppering the outsides or filling the bodies of their hosts with dozens of eggs. Other wasps evolved away from the practice, but the venomous stinger remains -- no longer an instrument of reproduction, but a potent biological weapon.

Wasp venom is produced inside a venom gland, then stored in a venom sack. From here, it seeps out through valves to coat a smooth, barbless stinger. The wasp keeps this wicked little weapon stored inside a sheath, ready to plunge it into prey or aggressors at a moment's notice. The males don't have stingers, but this doesn't stop them from bluffing. When cornered, male wasps have been known to brandish their harmless behinds in an empty threat.

But how does wasp venom work, and how can something so small hurt so much? Read the next page to find out.

Wasp Venom

Wasps' stingers are loaded with very potent venom, and unlike honeybees, wasps can sting a victim multiple times.
Wasps' stingers are loaded with very potent venom, and unlike honeybees, wasps can sting a victim multiple times.
©iStockphoto/Rhett Stansburry

A wasp's sting isn't the sort of thing most people take for granted, but the same can't be said for the chemical makeup of the venom. After all, why does a wasp sting hurt so much?

Wasp venom is far more than just stuff that hurts; it's a multi-step micro-assault with a twofold aim:

  • As an offensive weapon, the goal is to paralyze insects for easier transport back to the nest.
  • As a defensive weapon, the venom delivers enough pain to convince larger animals to leave well enough alone.

To get to the bottom of wasp venom, it's important to understand exactly what pain is: localized physical suffering associated with physical injury or disease. Basically, it's the nerves telling the brain, "Hey, your arm is damaged," or "Move, your leg is on fire." The intended result is that the creature experiencing the pain will fight or flee, whichever best removes the threat of more physical damage. For more information, read How Pain Works.

With wasp venom, the pain, which can be very intense, is an exaggeration of the actual physical damage, which is minimal. The sting enables the wasp to convince larger threats that it's capable of dishing out far more physical damage than one would expect from a creature so small. The message, often driven home with bright body coloration, is "leave us alone."

Wasp venom achieves this effect by waging a staged attack against the nervous system on a cellular level.

  1. The stinger delivers the venom to the victim's blood stream.
  2. Peptides and enzymes in the venom break down cell membranes, spilling cellular contents into the blood stream. When the cells in question are neurons, which serve the central nervous system, this breach causes the injured cell to send signals back to the brain. We experience these signals in the form of pain.
  3. To make sure the pain keeps coming, other substances in the venom, such as norepinephrine, stop the flow of blood. This is why the pain of a wasp sting can last for several minutes, until the blood stream can carry the diluted venom away.
  4. Finally, hyaluronidase and MCDP (mast cell degranulating peptide) pave the way for the membrane-destroying elements in the venom to move onto other cells by melting through the connective tissue between them. This spreading factor leads to the swelling and redness associated with most insect stings.

This sting accomplishes the goal of persuading most large animals not to try to kill or eat the wasp. Think of pain as a security system, only for your body. A wasp sting might not actually burn the house down, but it sure can set off all the alarms and sprinkler systems.

But there's much worse in store for the smaller victims of wasp stings -- the gory details of which we'll explore in the next section.

The Wasp Nest

Mason wasp larvae awaken to a delicious feast of paralyzed grubs inside their clay cylinders.
Mason wasp larvae awaken to a delicious feast of paralyzed grubs inside their clay cylinders.
Jef Meul/Minden Pictures/Getty Images

Modern parasitic wasps continue the practice of laying their eggs on or inside host insects they find, but most species long ago moved on to building nests. This method ensures the hatching young have the shelter of a protective structure, as well as adult wasps to guard them. A queen builds a cylinder, fills it with one or more paralyzed insects, then deposits an egg. When the egg hatches, the hungry larva feasts on the hapless victims.

The number of captured insects provided for wasp larvae varies from species to species. The black and yellow mud dauber (caementarium) will fill a larva's cylinder with about 40 spiders. Pepsis wasps (also known as tarantula hawks), on the other hand, will lay each egg inside a single paralyzed tarantula. The emerging larva will then proceed to eat the imprisoned spider from the inside out.

But don't cry over these entombed creatures. Wasps perform a beneficial service to humans by preying on potential pests, including the venomous black widow spider. Some farmers even ship in wasps to prey on grubs, caterpillars and boll weevils that would otherwise detroy crops.

There is also a great deal of variety to be found in the diet of each species' larvae. Adults subsist on pollen and nectar and almost always hunt only to feed larvae. With many species, individual wasps receive most of the nutrition they'll ever get in life as larvae.

While the exact architecture of wasp nests ranges from small underground structures to giant paper constructions, the size of nests can be easily divided between two kinds of wasp: social and solitary.

Solitary wasp queens build small, isolated nests, which they fill with eggs and food for the growing larvae. Social wasps, which account for only about 1,000 species of the vespidae family, follow a caste system consisting of one or more queens, male drones for mating purposes and a host of sterile, female workers to build the nest, hunt for food and tend to the growing larvae. Social wasps will attack furiously in defense of their nest when disturbed, communicating the threat to each other through the use of chemical signals called pheromones.

But a wasp nest is not a city. It's an undertaking with a single purpose: to ensure the production of young so the genetic line can continue into the next season. For this reason, the production of future queens takes priority over all else. This often means that, at the end of the nest's cycle, every member of the nest, except emerging queens, dies. In wintering areas, only queens will hibernate through the colder months to emerge again in the spring and start the cycle all over with a new nest.

 

Wingless wasps? Picnic-loving wasps? In the next section, we'll take a look at some noteworthy species -- including the wasp you can thank every time you tear into a package of Fig Newtons.

Types of Wasps

Female fig wasps emerge from holes bored by blind, flightless male fig wasps in Barro Colorado Island, Panama.
Female fig wasps emerge from holes bored by blind, flightless male fig wasps in Barro Colorado Island, Panama.
Mark Moffet/Minden Pictures/Getty Images

With so many species of wasps at large in the world, it's difficult to completely catalog their vast anatomical and social variety within a single article. So, we've chosen a few fascinating species for closer examination.

Fig Wasps

Why worry about delivering food to your larvae back at the nest when you can just build the whole nest inside your food source? Fig wasps accomplish just that. There are 900 species of fig wasp, and each is responsible for pollinating one or two species of fig plant. In this situation, both plant and insect have come to depend on each other in what is called mutualism.

A fertile female fig wasp will seek out the flowering parts of a fig plant, located inside of a fruit-like structure called the syconium. There, she lays her eggs and introduces pollen to fertilize the plant. The larvae feed off plant tissue and eventually hatch into new fig wasps.

But does this mean every time we chomp into a Fig Newton we're loading up on wasp carbs? No, because the fig plants that humans harvest produce two kinds of figs: edible figs and caprifigs. Females can only lay eggs inside caprifigs, so these quickly fill up with wasp eggs while edible figs only fill up with seeds. Learn more about fig wasps by reading Are figs really full of baby wasps?

Yellow Jackets

The bane of many picnic-goers, this social wasp's apparent fondness for sandwiches, barbecue and fried chicken often leaves the impression that they are primarily scavenging carnivores. But like most wasps, the only items they're really interested in are sugary teas and sodas. The meat isn't for them, it's for the larvae.

When they're not bothering picnickers, yellow jackets are busy hunting down a host of insects that frequently prey on cultivated plants. Yellow jackets pack a painful sting and will fight vigorously to defend their underground nest if disturbed. And since the average yellow jacket colony boasts a population between 2,800 and 5,000 wasps, it's best to step lightly when you spot their telltale yellow and black.

Cuckoo Wasps

These wasps figured out long ago that one of the best sources of food for their larvae was other wasp larvae. And what better way to feed them than by leaving the larvae in another wasp's nest to begin with. This brilliantly-colored deadbeat mom will lay her eggs inside the nests of solitary bees and wasps. When the cuckoo larvae hatch, they feed on the larvae and food left by the actual nest builders.

Velvet Ants

Despite their appearance, velvet ants are actually solitary wasps. While the males come fully equipped with wings, the females ditched the wings long ago to better pillage underground bee and wasp nests, where they lay their eggs to feed on the native larvae. Velvet ants pack a fearsome sting, and some are even capable of squeaking at perceived threats.

Despite the essential role they play in the ecosystem, your chief interest in wasps may be ridding yourself of them. Whether you love or hate wasps, learn how to manage them near your home on the next page.

Wasp Management

Is this yellow jacket a part of your yard or an enemy invader? You decide.
Is this yellow jacket a part of your yard or an enemy invader? You decide.
©iStockphoto/Kalvis Kalsers

Sure, wasps pollinate the plants responsible for beautifying your lawn, growing your food and producing your oxygen, but just who do they think they are buzzing around at your backyard pool party?

The first step in any attempt to manage a wasp problem is to realize there might not be a problem. Beneficial qualities aside, it's important to remember that even the more aggressive species will not attack you unless they feel you're threatening them or their nest. If they're just flying around, the wasps are probably looking for pollen or insects to feed their larvae; since you're neither of those things, you don't have to worry much. If one lands on you to check out a particular scent or color, don't panic. If you can avoid swatting it or making any swift movements, the wasp will quickly fly off and find something better to occupy its time.

If there seem to be too many wasps around, consider exerting your control over some of the factors that encourage them.

  • Avoid wearing white and yellow when outdoors, as these colors often attract insects.
  • Always wear shoes outside. If you happen to step on a wasp, she will try to sting you -- but can you blame her?
  • Cut down on the perfume. If you smell like flowers or sweets, you stand a good chance of attracting unwanted attention from the local wasp population.
  • Consider moving flowers away from the house, as wasps love these types of plants.
  • Cover your garbage can. This not only keeps the wasps out, it also keeps out the insects that wasps hunt.
  • Knock down vacant nests during the winter. This prevents wasps such as mud daubers from returning to the same construction in the spring.

Likewise, if wasps have built a nest nearby, consider simply leaving them alone there. They will protect their turf if threatened, but they built the nest to raise their young -- it's not a launching pad for a wasp war on all humans.

Sometimes, wasps will build nests in inconvenient places, or their numbers will be too great for cohabitation to remain a viable option. If wasps need to go, consider the scope of any attempt to exterminate or remove them. If the nest is large and occupied by social wasps, such as yellow jackets or hornets, consider hiring professional pest controllers. Even with smaller nests, be sure to wear padding and eye protection -- not just against stingers but also against any store-bought insecticides you might be spraying into the air. And remember, if you kill a wasp near the nest, the wasp's death will release chemical signals which will signal the other wasps to attack.

While a can of insecticide and a broomstick may seem like the perfect weapons against a nest, consider some of the more preventative measures available. Various traps are readily available and can cut down on the number of wasps buzzing through your yard, especially if placed early in the season so as to catch emerging queens. Wasps are drawn into the traps via bait and then can't escape.

The key, of course, is to pick your battles. Know when wasps are truly pests and when they are valuable members to your backyard ecosystem. And, if you decide they must go, know when you're outgunned. To learn more about wasps, visit the links on the next page.

Related HowStuffWorks Articles

More Great Links

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