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In anticipation of the 33rd Annual Insect Fear Film Festival, which they will host Saturday on the UI campus, this week's column is written by three members of the Entomology Graduate Student Association: Joshua Gibson, Todd Johnson, and Tanya Josek

The theme of this year's Insect Fear Film Festival is 'exploding arthropods!' While our feature films may be a bit far-fetched, exploding insects are very much grounded in reality. Here we present a few examples of insects exploding or causing explosions, and why they do it.

Bombardier beetles

One day Charles Darwin was returning from a collecting trip when he spotted an interesting beetle. His hands were full so he decided to put the beetle in his mouth to transport it back to camp. While inside, the beetle released an explosive chemical reaction causing Darwin to drop all of the insects he collected that day. We now know these insects as bombardier beetles, which get their name from a unique ability to direct a hot spray of chemicals from their posterior end. The explosion is initiated by a reaction which causes a chemical mixture to heat up and become caustic. Recently, researchers found that these beetles open and close a valve inside their body while spraying, causing the spray to come out in a series of pulses. The pulses probably help protect the beetles from damaging themselves by limiting their exposure to the reactive chemicals. For bombardier beetles this is a very effective defense against predatory animals that might be looking for a quick meal.

Exploding ants

In the forests of southeast Asia, it's an ant-eat-ant world. Arboreal ant communities are often dominated by species with large, aggressive colonies, and it can be difficult for many species to establish nests. To do so requires a good defense ...but sometimes a good defense is a good offense. Exploding carpenter ants, Camponotus saundersi, have evolved a unique way of defending their nests from attack. When threatened, worker ants can compress their abdomens and cause dangerous chemicals to burst from their heads. This often kills nest intruders at the cost of the workers' own lives. The ruptured ants stop scouts of more aggressive ant species from informing the rest of their colony of this valuable nest location, preventing a large-scale invasion. By sacrificing their own lives for the good of the colony, C. saundersi workers allow their colonies to stand tarsus-to-tarsus with more aggressive ants and live to tell the tale — even if some of the workers themselves do not.

Parasitoid wasps

The science fiction hit "Alien" terrified audiences with the idea of aliens bursting out of astronauts. While most of the movie is fiction, some of the biology is not. Many arthropods experience a similar phenomenon. As eggs, larvae, or adults they can be susceptible to attack by parasitoids, insects that lay their eggs inside or near the bodies or eggs of other arthropods, ultimately killing them. One of these parasitoids, the tiny wasp Cotesia congregata, seeks out tobacco hornworm caterpillars to attack. When a female wasp finds a suitable caterpillar, she uses her stinger to inject eggs inside the caterpillar before flying away. The caterpillar continues to eat and grow, unaware that wasp larvae are growing inside its body. Once the larvae fully develop, they chew their way out of the caterpillar's body and spin cocoons, eventually emerging as adults. Shockingly, the caterpillar is alive throughout this entire process and only dies after the wasps have completed development. As you can see, both Alien and the wasp Cotesia congregata share many similarities during development, rooting the movie's premise in reality.

Exploding arthropods are more real than they may appear. We hope you enjoyed reading about some interesting examples of explosions in action. Please feel free to suspend your disbelief further as you enjoy some great explosions in our 'Exploding Arthropod Fear Films.'

Doors to Foellinger Auditorium open at 6pm with an insect petting zoo, face-painting and balloon insects, insect-related artwork, and our first ever "talking cockroach." An introduction by Entomology department chair, May Berenbaum, will be given at 7:00 and the films start at 7:30. For more information visit IFFF on Facebook ( or their website (

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