Spider Wasp (family Pompilidae)

The other night I had a nightmare about spiders. This isn’t all that unusual, as almost every nightmare I have has something to do with spiders. Still, it left me feeling particularly unfriendly towards my arachnid nemeses, so today I’m going to write about animals that are particularly nasty to spiders.

Spider wasps belong to the family Pompilidae, which is composed of around 5,000 species. There are six subfamilies of spider wasps, with Pepsinae and Pompilinae containing the most species. As one might expect with such a large family, spider wasps range across most of the world.

Most spider wasps are black in colour, with markings that can be orange, yellow, white or red. They range in size from 5 to 50 mm, with female wasps usually being larger than males. Spider wasps don’t look particularly fearsome, with their slim bodies and skinny legs. Most species have long, slender wings, though some have short wings and some have no wings at all.

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A quite pretty spider wasp. Image credit: Vijay Cavale via Wikipedia

Though they hunt spiders, adult spider wasps are actually mostly vegetarians, eating nectar and other plant-based foods. They hunt spiders to help me sleep better at night, and to feed their young. Females paralyze their victims with a nasty venomous sting. These stings can be very painful to humans — tarantula hawks are known to have the second most painful insect sting in the world, behind bullet ants.

Once a spider is paralyzed, spider wasps have to drag it back to a pre-made burrow. Some species are lazy about this, and so will wait to catch a spider to dig a burrow. Others are even lazier, and use the spiders’ own nests burrows. After the spider is safely tucked into the nest, the female will lay a single egg on the spider. She then closes up the burrow, and some species will even put dead ants behind the entrance, to deter predators.

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A lovely photo of a spider wasp dragging a spider back to its nest. Image credit: Tony Wills via Wikipedia

The really nasty part of spider wasp biology happens after the egg hatches. The larval wasp immediately starts to feed upon the still-living spider. Some species of wasp paralyze their prey temporarily, which means the spiders will regain activity and slowly be eaten by the parasitic wasp larva. The larva is quite selective about what parts of the spider is eats, leaving the heart and nervous system for last. This keeps the spider alive as long as possible, so it doesn’t decompose before the larva is ready to pupate. Once the the larva has eaten all the tasty spider parts, it will spin a cocoon, and then emerges as an adult the next summer.

I’m not sure I’d want to run into any spider wasps — the sting of the tarantula hawk definitely sounds like one I’d like to avoid. Still, I can appreciate the way these insects treat spiders, so they’re right up there as some of my favourite animals.

Cover image credit: Alvesgaspar via Wikipedia

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