A cockroach and a jewel wasp are locked in a battle, but not for long. The wasp latches onto the cockroach, arcs her body, and inserts her stinger precisely into a cluster of nerves in the cockroach’s thorax. The venom that surges out temporarily paralyzes the cockroach’s front legs. She then stings its brain, where her venom blocks its fight-or-flight response. From here on out, the cockroach is essentially a zombie.
The wasp snaps the cockroach’s antennae in half, uses the broken pieces as straws to feed off its blood-like hemolymph, and then leads it into a subterranean lair. She lays an egg on her victim and carefully seals the burrow, which becomes her offspring’s nursery and the cockroach’s crypt. Over the following weeks, her larva hatches bores into the cockroach, eats it alive, pupates in its carcass, and emerges as an iridescent adult. This gruesome tale is just one example of parasitoidism, an evolutionary strategy employed by most wasps. Parasitoids feed off other animals as they develop, usually killing their hosts in the process.
This wasp targets the ladybug, planting an egg inside its body. When the larva hatches, it consumes the beetle’s body fat. It eventually emerges, but the ladybug’s duty isn’t done. It’s now semi-paralyzed, possibly due to a viral infection the wasp gave it. The larva spins a cocoon between its legs, and the still-alive-but-bewitched beetle stands guard. When a predatory lacewing larva approaches, the ladybug twitches, scaring it off. Many other creatures avoid the ladybug altogether because of its bright coloration, which advertises its toxicity. After a week, an adult wasp appears, leaving its hapless helper’s corpse behind.
Next is the tiny but fierce crypt-keeper wasp, which targets gall wasp larvae like this one. The gall wasp larva is also parasitic but in a more vegetarian sense. It’s feasting on this oak tree, tucked away in a chamber on one of its branches. Soon, it has company. The crypt-keeper wasp adds her egg into the mix. The gall wasp develops and eventually begins chewing its way out, as it normally would. But it makes a smaller-than-usual hole and gets stuck. The crypt-keeper larva eats through the gall wasp’s corpse, pupates within it, and then makes its debut, crawling out of the dead wasp’s head.
The final victim is this caterpillar. It would have become an owlet moth that fluttered in the cool night air, but a few weeks ago, while developing in its egg, this wasp injected an egg of her own. The caterpillar hatched and began growing. And in a process called polyembryony, the wasp spawn divides repeatedly inside of it. But a second kind of wasp also lays her eggs on the caterpillar. The original brood senses this and further develops into two distinct castes. What was one egg becomes thousands of larvae: some of them are reproductives, others are soldiers. The caterpillar is now both a wasp buffet and a battleground. As the reproductive larvae consume its insides, the soldiers kill the other parasitoids. The reproductive larvae morph into adults and the soldiers die within the host. Needless to say, the result for the caterpillar is … very bad.
This was just a peek into the prolific province of parasitoid wasps. Some venture underwater to find their hosts. Others are hyperparasitoids, whose victims are other parasitoid wasps. Scientists are still pulling back the curtain on these creatures. They can be hard to collect and quite small: the world’s tiniest known insect is a microscopic wasp that parasitizes barklice eggs. Though much remains unknown, some researchers suspect that parasitoid wasps are among the most diverse animal groups—perhaps the most diverse. Wasps have been perfecting their brand of parasitism for some 247 million years, all to give their offspring the very best opportunities life has to offer.
Illustrate the battle between a cockroach and a jewel wasp. Show each step of the wasp’s strategy, from stinging the cockroach to the emergence of the adult wasp. Use captions to explain what is happening in each panel.
Pair up with a classmate and take turns acting out the roles of the cockroach and the jewel wasp. Use props or simple costumes to make it more engaging. Describe your actions and explain the biological processes involved.
Write a diary entry from the perspective of a parasitoid wasp. Describe a day in your life, focusing on how you find and parasitize your host. Include details about your interactions with other creatures and your environment.
Create a quiz with questions about the different parasitoid wasps mentioned in the article. Include multiple-choice, true/false, and short answer questions. Exchange quizzes with a classmate and see who can score the highest.
Construct a food web that includes the parasitoid wasps and their hosts. Use images or drawings to represent each organism and show the relationships between them. Explain how the wasps fit into the larger ecosystem.
Cockroach – A large insect with long antennae and legs, typically feeding and living in warm, dark conditions. – The cockroach scurried across the kitchen floor, causing a scream of terror.
Jewel wasp – A type of wasp known for its metallic coloration and its unique behavior of using cockroaches as a host for its larvae. – The jewel wasp stung the cockroach, paralyzing it before laying its eggs inside.
Battle – A violent confrontation or struggle between individuals, groups, or nations. – The two armies engaged in a fierce battle, with swords clashing and arrows flying through the air.
Venom – A poisonous substance secreted by animals such as snakes, spiders, or scorpions, typically injected into prey or enemies. – The snake’s venom quickly paralyzes its prey, allowing it to consume it at its leisure.
Nerves – The bundles of fibers that transmit signals between the brain or spinal cord and other parts of the body, allowing for communication and control. – Her nerves tingled with anticipation as she stepped onto the stage to perform.
Thorax – The middle section of an insect’s body, between the head and the abdomen, to which the legs and wings are attached. – The bee’s thorax moved rhythmically as it buzzed from flower to flower, collecting nectar.
Zombie – A fictional undead creature that is typically depicted as a reanimated corpse, often associated with mindless behavior and a craving for human flesh. – The zombie shuffled through the deserted streets, its vacant eyes searching for its next meal.
Parasitoidism – A type of parasitism in which the parasite eventually kills its host, often by consuming it from within. – The wasp’s parasitoidism led to the demise of the cockroach, as its larvae fed on its internal organs.
Larva – The immature form of an insect or other animal that undergoes complete metamorphosis, typically different in form and habits from the adult. – The butterfly larva, or caterpillar, voraciously ate its way through the leaves of the plant.
Pupates – The process by which an insect undergoes the transformation into its adult form while enclosed in a protective case called a pupa. – After spinning its cocoon, the silkworm pupated and eventually emerged as a beautiful moth.
