Black Ichneumon Wasp with long ovipositor

The Ichneumon Wasp

Ichneumon Wasps

Matthew Hess

Some insects strike fear in the mind of humans. This is especially true of insects like the Ichneumon wasp. Insects with intimidating characteristics typically either scare or fascinate people! Often, when we are faced with such an insect and have little to no knowledge about it, our minds take us to a worse-case scenario, where we imagine some ridiculously unlikely possibilities.

For instance, you go to the mailbox to check your mail and BAM! A black spider with a red or white spot on its back, jumps out of the way. By the time you have slammed the mailbox door shut, your mind has convinced you that you were almost attacked by a venomous Black Widow!

I’ve heard this story more than a few times from customers… (and my wife!). Yet, the facts always end up being much less entertaining. In most cases, it was just a simple jumping spider. It also wasn’t jumping at you but away from you. And it actually looks nothing like a Black Widow! The truth about jumping spiders is that they are actually BENEFICIAL! They are even known to hunt, kill and feast on the venomous Brown Recluse! So even if we leave out the fact that you pose a great deal more threat to the spider than it does to you, having knowledge about the jumping spider can reduce the anxiety which accompanies seeing one.

Ichneumon wasps can have this effect on people as well. Especially when they are discovered indoors. With their specifically aggressive looking characteristics, they can be very intimidating to someone who knows little to nothing about them. In this article, I hope to help you better understand this very harmless and beneficial insect.

What Is an Ichneumon Wasp, Anyway?

Ichneumon wasps are solitary insects belonging to the largest and most diverse animal family called Ichneumonidae. Ichneumonidae, in turn, belongs to the order, Hymenoptera, along with ants, bees and other wasps. (For proper pronunciation, click HERE for Hymenoptera or HERE for Ichneumonidae). There are between 60,000 and 100,000 known species worldwide. More than 5,000 of those reside within the United States.

Because they somewhat resemble their close cousins, stinging wasps, Ichneumon wasp sightings can be unnerving. However, closer observation can quickly set them apart from a paper wasp.

Personally, I have had customers refer to them as wasps, giant mosquitoes, mayflies and my favorite, “those huge mosquito looking bugs with a long stinger” (by the way, that “long stinger” is actually no stinger at all). But, at nearly the length of the entire body and sometimes longer, this stinger-looking appendage will give a person a really good reason not to handle one!


The name “Ichneumon” is derived from the Greek language, specifically, the Greek word which means “footprint” and “tracker”. The female wasp is to credit for this well-deserved name. She literally hunts and tracks down viable hosts in which she will deposit her parasitic offspring. But not to worry; you won’t soon become an Ichneumon wasp host!

In the modern world, the Ichneumon Wasp was first described by Carl Linnaeus in 1758. However, it’s likely the Ichneumon Wasp family has been known and studied by scientists and naturalists for many centuries prior. It’s quite possible that the benefits of the Ichneumon wasp were even known long before Linnaeus first described them. After all, many advanced civilizations have risen and fallen before we came along!

Equally as plausible is the possibility that the knowledge of their benefits is something only discovered since their first modern description. It could be that we know something our ancestors had no idea about! But even if we don’t, it’s important for us to know at least a few informative details about them.


Ichneumon wasps have a characteristic slender and elongated body, with a narrow waist and long antennae. They have a variety of body colors, ranging from black and yellow to brown and red and even yellow stripes, like some paper wasps. The females of some species have a long, thin ovipositor that they use to lay their eggs in or on the body of their host. It’s capable of piercing wood and can be as long as four inches!

The ovipositor of the Ichneumon Wasp is what many mistakenly call a “long stinger”. In some species, the insect itself can measure in at around 1 ½ inches, though some are much smaller. The ovipositor can be as long or longer than the body. Couple these facts with the overall wasp-like appearance of the Ichneumons, and it’s not hard to see why they are often confused as dangerous or threatening. Yet, that is far from the truth, at least for humans!

Blak and Yellow-striped Ichneumon Wasp

Pictured, a black and yellow-striped Ichneumon Wasp


As a parasitic wasp, the Ichneumon female uses her ovipositor to lay her eggs in or on the body of a single host. Another insect, typically a caterpillar or grub, will serve as the perfect host for their larvae. Some species lay their eggs directly in the host, while others lay them on leaves near the host and wait for the larvae to find the host on their own. Several species of Ichneumons require a specific insect as a host. Besides caterpillars and grubs, Ichneumon eggs can be laid in the larvae of several insect families.

These include:
  • Beetles – Order Coleoptera
  • Butterflies and Moths – Order Lepidoptera
  • Ants, Bees and Wasps- Order Hymenoptera (yes, their own order)
  • Flies – Order Diptera
  • Spiders – Order Araneae
Life Cycle

Often, Ichneumon females may be found along the bark of trees where they use their antennae in search of wood-boring larvae just beneath. If she finds one, she will use her ovipositor and push through the bark and into the larvae where she will lay her eggs. The life cycle involves an egg, larva, pupa, and adult stage. Once the larvae emerge from the eggs, they feed on the host insect until they are ready to pupate. Usually by this time, the host insect is dead.

Once the pupae emerge from the dead or dying host insect, they develop into adult wasps, and continue the cycle of reproduction. While the larvae of the Ichneumon wasp feed on grubs, caterpillars or other types of larvae, the adult feeds on a variety of nectars and other sources of sugars. These provide the adult with the energy and stamina necessary to reproduce. The length of the life cycle can vary greatly depending on the species and environmental conditions.

Black Ichneumon Wasp uses ovipositor to pierce bark to reach host

Here, a black Ichneumon Wasp female uses her ovipositor to pierce bark and inject her eggs into a host insect beneath.

Red Ichneumon Wasp on white background
Ichneumon Wasp Life Cycle Chart


Ichneumon wasps are typically found in environments with a diverse range of their preferred hosts, as well as a source of nectar and other food sources for the adults. These environments include geography with abundant vegetation. Such vegetation provides a plentiful source of hosts, readily available protection and a variety of nectars. As one of the most common insects in the world, they can be found in almost all habitats.


Ichneumon wasps are not typically dangerous to humans. Though some species can sting, even those rarely do. If you are unfortunate enough to be among the handful of humans ever stung by an Ichneumon wasp, you’ll be happy to know that its sting has no venom. However, with an ovipositor the same length or longer than its body, it’s no wonder that some people are on high alert when they see one in their home.

Though sometimes mistaken for something other than what it is, an Ichneumon Wasp is actually no pest at all. Instead, it’s a beneficial insect that we should all be thankful for. It’s one of the very few insects which hunt and kill pest insects and doesn’t subsequently become a pest itself. That’s a tall order for a bug!

Role in the Ecosystem

Ichneumon wasps play an important role in controlling insect pests and maintaining the balance of ecosystems. They are natural predators of many pests, including caterpillars, grubs, and other insect larvae, as I mentioned earlier. By controlling these pests, Ichneumon Wasps help to regulate populations and prevent them from causing damage to crops and other plants. They also serve as a food source for birds and other predators, helping to support the food chain.

They only accidentally wander indoors and have no desire to be there. Typically, this might happen at night when they are attracted to an outside light affixed to the house, or maybe to a window which lets light shine through. The wasp is simply attracted to the light and once a door is opened, it may fly in to get closer to that light.


Their characteristics, complex biology, diversity, wide range of habitats, life cycle, and reproductive strategies, make them among the top contenders for “most interesting insects”. Pair these facts with the insect’s role in controlling pests and maintaining the balance of ecosystems, and you have yourself an insect whose very existence is a crucial part of the natural world. Their role as biological pest control agents makes them one of my favorite insects. That’s a short list to be on and they are at the top of it!