You feel almost nothing at first… Maybe a slight poke or prick, nothing of consequence – you figure you probably just brushed up against a twig or something. Soon you start to feel sluggish, maybe unwell, not at all like yourself. You start to notice a squirming, gnawing feeling internally. It gets worse… And worse… You finally realize what’s going on. You are slowly being eaten from the inside out. While still alive! 😱 And there is absolutely nothing you can do about it.
If that doesn’t sound like something straight out of a Sci-Fi horror movie (like Alien perhaps?), I don’t know what does. What to hear something really terrifying? These sneaky creatures, that eat you from the inside out while you’re still alive, are real and found almost everywhere around the world! Want to know what they are? You’ve probably been living right next to them for ages… These horrifying sounding creatures are actually Ichneumonid Wasps. Thankfully, Ichneumonid Wasps are not only harmless, they are actually beneficial. Unless you are a caterpillar that is!
Ichneumonid Wasps (family = Ichneumonidae), also sometimes called Darwin Wasps, are a type of “parasitoid” wasp, meaning they need a host organism to complete their life cycle. Unlike predatory wasps, like yellowjackets or paper wasps, Ichneumonid Wasps can’t really sting humans. Even though they may have what looks like a stinger, the stinger-like structure (ovipositor in bug nerd talk) on their rear end doesn’t have the same venom, or stinging power, as on hunting wasps and is only used for laying eggs. Supposedly, the larger ones can give you a bit of a jab with their ovipositor (although I’ve never had the pleasure), but the smaller ones just don’t have the strength to break human skin (try as they might to fake you out!). Ichneumonid Wasps don’t actually have any need for a “stinger” anyway. They are generally solitary creatures and don’t have any nests to defend like the typical hunting and social nesting wasps folks usually think about.
These horrifying, yet beautiful (in my opinion :) ), wasps are all about stealth and sneakiness. Ichneumonids will usually locate an appropriate host by sniffing them out – either by “smelling” the chemicals emitted by the host itself, by smelling the chemicals emitted by the plant the host is chowing down on. How cool is that? The word “ichneumon” actually means “track” in Greek, which seems totally appropriate given their sniffing skills. Maybe Ichneumonids should have been called “tracker wasps” or “bloodhound wasps”? Ah well, probably too late now.
Once the Ichneumonid finds a host it wants, the female will lay its eggs either on top of, or inside the host. Quick in and get out again when possible (for safety’s sake). Where (on versus in) it lays its eggs, and on what creature, depends on the particular species of Ichneumonid Wasp it is. Also dependent on the species, is whether the host becomes mostly paralyzed when the eggs are laid, or whether the host continues to grow and develop while being eaten alive. Most Ichneumonids choose hosts that are easy targets like larvae or immature insects (aka baby or juvenile bugs) that are eating our plants. These are usually things like caterpillars, grubs, or maggots, but some Ichneumonids prefer host that are soft bodied adult bugs like aphids and mealy bugs, or occasionally even spiders. Sorry, I don’t know what species I have in my photos to help determine what their host is. Ichneumonid Wasps are notoriously difficult to identify, even by experts under a microscope, and I didn’t want to take them away from pollinating my herb flowers…
Because Ichneumonids are so good at finding their hosts by smell and don’t have to actually see them, Ichneumonids can usually find caterpillars and other soft bodied things that other predators can’t. Like caterpillars hiding in rolled up leaf nests, or grubs deep within plant stems, or even trees. While these wasps may sound horrific in the way they eat their hosts, because they are so good at finding their hosts (which are usually pest insects), Ichneumonid Wasps are really one of nature’s best-kept pest control secrets. Without Ichneumonid and other parasitoid wasps, our gardens, farms, and forests would be quickly overrun with hungry caterpillars and other soft bodied pest bugs.
So next time you see one of these deathly creatures hanging out around your garden looking for a host, pollinating your flowers, or sunning on the wall of your house - swallow your fear! Remember they can’t hurt you, and give them a little thank you for keeping the ecosystem in balance.
Want to learn more about Ichneumonid Wasps? Check out:
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Researchers are constantly trying to learn more about species and the insect diversity around us. Sometimes there is by-catch from these studies or the specimens are no longer needed after the research is complete. When this happens, I try to recycle the specimens. Here are some recycled specimens looking for a forever home:
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