Wasp Out for These Wasps!

 (Spider wasp carrying spider, Photo by Hans Christoph Kappel)

We’ve all had that tense moment when a wasp flies by our heads. Our first instinct is to duck, cover all our vital organs (the face), and run! Of course, even though we know that most things are more scared of us than we are of them, it does not change how we respond, but there is good news! A group of wasps (Family Pompilidae), also known as “spider wasps” or pompilids, are actually our saviors. 

You may be asking, "Where is the good news? They can still sting us!"

You are right! (kinda..) These wasps actually help lower the population of some of our greatest enemies, SPIDERS!

Pompilids actually use spiders to lay their eggs, they do not eat them (most feed on plant nectar). After mating, the females will begin their hunt for a spider. Once they locate one they use their long and muscular abdomens to inject venom, through a stinger, ultimately paralyzing it. Instead of eating them, the females will actually carry the spider back (while flying!) to a previously dug burrow or use the burrow of the spider. Then the wasp will lay a single larva egg on the abdomen of the spider and bury the spider. When the egg hatches the larva will begin feeding upon the spider until it is large enough, reaching its fifth instar, to build a cocoon. After a short while and metamorphosis, the larva emerges from its cocoon as a wasp and to repeat the process! Spider wasps are found all over the world and feed on many different types of spiders.

Where did they come from? 

Scientists believe that Pompilids have been around for about 65.5 million years. The oldest Pompilidae specimen on record originates from the Cretaceous period, suggesting that the first pompilids split off from very early Vespoids. During this time period, common ancestors of spiders are believed to have adapted to new food sources, prompting the coevolution of pompilids to specialize upon spiders. The continuation of such rich prey fauna has led to the highly diverse family of Pompilidae that we have today. This diversity allows them to live in a variety of habitats and have many specialized prey. 

(Tarantula Hawk, Photo by Eric Lowenbach)

Dangerous Species? 

A well known member of Pompilidae is Pepsis grossa, otherwise known as the “Tarantula Killer” or the “Tarantula Hawk”. These parasitic flyboys pack a big punch in the form of a paralyzing stinger. It has been coined by many individuals as “the most painful sting on the planet” right up there with the bullet ant and the velvet ant. True to its name, these wasps target the large spiders known as tarantulas. Although outmatched in size and strength, the wasp is specialized to taking on tarantulas thanks to its big ole stinger! Talk about an underdog! The wasp lays its egg on the spider’s abdomen and then buries the egg and the spider in a hole. This provides the wasp larvae with plenty of nutrition.

These beautiful but deadly pompilids live all over the globe. In the U.S., they are most commonly found in the southwestern deserts. Tatantula hawks have blue metallic bodies with rust colored wings. They are some of the largest known species of wasps and the females can be up to 5 cm in length. feed on the nectar of various flowers. The difference between the male and female is the fact that females have stingers and are the ones who hunt the spiders, whereas males do not. Watch out for that female stinger that can reach up to 7 mm (1/4 of an inch) in length! The sex of the spider wasp larvae, and ultimately the adult, is determined by whether or not the egg is fertilized. If the egg is fertilized, the larvae will be female. If not fertilized the larvae will be male.

Unique Behaviors Among Pompilids

Recent studies have shown that certain species of Pompilidae are quickly spreading farther north. With such diversity, there will inevitably be competition between species. One way to reduce competition to is find a new way to reproduce and find food, all the while reduce energy consumption. Brood parasitism is one way to achieve this and has been observed in several genera within Pompilidae. This parasitism usually takes place in one of two ways: one wasp will paralyze a spider and another species will attempt to take the prey from the first wasp, or a pompilid will wait for a female (of a different species) to capture a spider and deposit her egg and leave. Then the parasitic wasp will dig out the spider, destroy the previously deposited egg, lay her own egg and re-cover the spider. While these phenomena have only recently been observed, it reinforces the idea that Pompilidae and all hexapods are continuing to evolve and coevolve with their prey and predators.

Contributors: 
Patrick Lunn, Jacob Grimm, and Ben Book

Sources for pictures in order they appear:

http://ichef.bbci.co.uk/naturelibrary/images/ic/credit/640x395/s/sp/spider_wasp/spider_wasp_1.jpg

http://www.mysanantonio.com/news/local/article/Wasp-with-traumatically-painful-sting-comes-to-6346709.php

Sources:

Engel, Michael S., and David A. Grimaldi. The First Cretaceous Spider Wasp (Hymenoptera: Pompilidae). Journal of the Kansas Entomological Society, vol. 79, no. 4, 2006, pp. 359–368. www.jstor.org/stable/25086347.

Karsai, Istavan, Somogyi, Kalman, and Hardy, Ian C.W. Body Size, Host Choice and Sex Allocation in a Spider-Hunting Pompilid Wasp. Biological Journal of the Linnean Society, vol 87, 2006, pp. 285-296

Shimizu, Akira, Nishimoto Y., Makino, S., Syama, K., Okabe, K., and Endo, T. Brood Parasitism in Two Species of Spider Wasps (Hymenoptera: Pompilidae, Dipogon), with Notes on a Novel Reproductive Strategy. Journal of Insect Behavior, 2001.

Schimdt, Justin O. The Sting of the Tarantula Hawk: Instantaneous, Excruciating Pain. Undark.org. Undark, Inc. 2016.  

Spider Wasp. Encyclopedia Brittanica. Encyclopedia Brittanica, Inc. 1998. 

Staab, Michael, Ohi, Michael, Zhu,Chao-Dong, and Klein Alexandra-Maria. A Unique Nest-Protection Strategy in a New Species of Spider Wasp. Public Library of Science, 2014. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0101592