Yes, wasps eat caterpillars, and they do it in two very different ways. Social wasps like paper wasps and yellowjackets actively hunt caterpillars, chew them up, and feed the pieces to their young. Parasitoid wasps take a slower, more gruesome approach: they lay eggs inside or on a caterpillar, and the wasp larvae gradually consume it from within. Both strategies make wasps one of the most effective natural predators of caterpillars in gardens and wild ecosystems.
How Paper Wasps Hunt Caterpillars
Paper wasps are among the most dedicated caterpillar hunters in the insect world. Native North American paper wasps feed exclusively on caterpillars, making them highly effective pest controllers. The European paper wasp, now widespread across the continent, has a slightly broader diet that includes caterpillars plus other small, soft-bodied insects.
The process is straightforward but brutal. An adult paper wasp locates a caterpillar, kills it, and chews the body into a soft pulp. She then carries this chewed-up material back to the nest and feeds it directly to the developing wasp larvae. Adult wasps themselves primarily drink nectar and other sugary liquids for energy. The caterpillar meat is protein for the next generation.
This hunting behavior is so intense that it can affect caterpillar populations at a local level. Multiple studies have found that European paper wasps negatively impact monarch caterpillar populations, particularly in urban areas where wasp numbers are high and caterpillars are concentrated into small patches of habitat. If you’ve noticed fewer caterpillars on your milkweed plants, nearby paper wasp nests could be part of the reason.
Parasitoid Wasps: Eating From the Inside
Parasitoid wasps don’t hunt caterpillars the way paper wasps do. Instead, a female wasp lands on a caterpillar, paralyzes it briefly, and deposits her eggs inside the caterpillar’s body. The caterpillar survives initially and continues feeding as though nothing happened. But inside, wasp larvae are hatching and slowly consuming the caterpillar’s tissues.
This internal feeding can go on for days or weeks. The wasp larvae are selective about what they eat first, avoiding vital organs so the caterpillar stays alive as long as possible. When the larvae are fully grown, they chew through the caterpillar’s skin, emerge from the body, and spin tiny cocoons on the outside. At this point, the caterpillar typically dies.
Some parasitoid wasps develop externally rather than internally. These species attach their eggs to the caterpillar’s surface, and the larvae feed from the outside. Either way, the result is the same: the caterpillar serves as both food and shelter for the developing wasps.
Which Caterpillars Get Targeted
One of the most well-known examples is the braconid wasp Cotesia congregata, which targets more than a dozen species of sphinx moth caterpillars. Its most common host in the southeastern United States is the tobacco hornworm, the large green caterpillar that devours tomato, pepper, and tobacco plants. But it also parasitizes caterpillars of the Virginia creeper sphinx, the snowberry clearwing, the catalpa sphinx, and several others. It even attacks a few moth caterpillars outside its primary host family, including the cabbage looper and the fall armyworm.
Gardeners who grow tomatoes have likely seen the results firsthand. A hornworm covered in dozens of small white, rice-shaped cocoons clustered along its back and sides is carrying braconid wasp pupae. Those aren’t eggs the caterpillar laid. They’re wasp larvae that fed inside the hornworm, chewed their way out through the skin, and spun cocoons on the surface. The adult wasps that emerge are tiny, less than an eighth of an inch long, black-brown with reddish markings.
What to Do With Parasitized Caterpillars
If you find a caterpillar in your garden covered in small white cocoons, leave it alone. Those cocoons will produce adult wasps that go on to parasitize more pest caterpillars. Removing or killing a parasitized hornworm means destroying dozens of beneficial wasps before they can hatch. The caterpillar is already doomed and has mostly stopped feeding by the time the cocoons appear.
This is one of the key reasons integrated pest management programs encourage gardeners to tolerate some level of wasp activity. Paper wasps nesting near a garden actively patrol plants for caterpillars. Parasitoid wasps work more quietly but can suppress caterpillar populations over time without any intervention on your part.
How Caterpillars Fight Back
Caterpillars aren’t defenseless against wasp attacks. Many species have evolved sophisticated survival strategies. Some caterpillars can actually detect the sound of a wasp’s beating wings in the air and respond with rapid jerking movements designed to knock the wasp away or make egg-laying difficult.
Group-living caterpillars have an advantage. Clustering together creates a simple dilution effect: the more caterpillars in a group, the lower the odds any single individual gets targeted. Some social caterpillars take it further with synchronized body rearing, flicking, and mass regurgitation of toxic or foul-tasting chemicals that deter predators. When one caterpillar in a colony detects a threat, vibrational signals travel through their shared silk web to alert the entire group.
Shelter-building caterpillars use a different approach entirely. Some species construct tough silk nests that are nearly impenetrable to both birds and wasps, then only leave to feed at night when predatory wasps are inactive. These physical barriers and behavioral shifts represent an ongoing evolutionary arms race between caterpillars and the wasps that depend on them for food.