A fly seems to be balancing not on its legs but on its wingtips.

Call CSI: It’s an Insect Murder Mystery

A strange-looking fly caught my eye.

It stood upright, balanced not on its legs but on its wingtips. I leaned in for a closer look.

The fly wasn’t standing. It wasn’t even alive.

The poor creature had been stabbed.

The perpetrator, an assassin bug, had impaled the fly with its sharp, hollow beak. That beak does triple duty. First, it pierces the bug’s prey. Then, it injects saliva loaded with enzymes that paralyze the prey and liquefy its insides. Finally, the beak becomes a straw, and the bug drinks its juicy meal.

An adult assassin bug on a leaf.
Adult Zelus luridus, aka Pale Green Assassin Bug (which isn’t necessarily pale green)

I knew that assassin bugs turn their prey into juice boxes. I see occasional adults in summer and plenty of the young nymphs in early fall. But until last week, I’d never seen an assassin bug at mealtime. You might be thinking yuck. But I was mesmerized as I watched the bug eat.

Here’s a view of the bug’s beak inserted in the fly’s belly.

And here’s a short clip of the bug maneuvering its meal as it eats. After the video, I’ll share what puzzled me as I watched this happen.

How the heck did this little, wingless bug manage to catch that big, fat fly? The assassin bug was a nymph, too young to develop wings. I found the pair on the pavement, smack in the middle of our driveway. You can see the bug is strong enough to push and pull its prey. But how did it trap and hold the fly long enough to inject it with paralyzing venom?

Well, it turns out that older nymphs and adults have front-leg glands that produce a sticky substance. This goo coats the bugs’ leg hairs and gives them a good grip. Hatchlings can’t yet produce the goo. But their mothers leave lots of it behind on the egg case. The little ones smear their legs with the sticky stuff before leaving to find food.

Assassin bugs skulk around in flowers and foliage. They use an ambush technique to trap their prey. Adult assassin bugs have wings, so I was surprised to learn they rarely use them while hunting. Like the nymphs, they prefer to play hide-and-trap. Assassin bugs are beneficial in the garden, as they eat lots of nuisance plant eaters, like aphids.

So… now we know how the bug caught the fly. But where did the ambush happen? Surely not in mid-air. Probably not on the pavement. I’m guessing the bug was hunting in the treetops by the driveway. Perhaps a puff of wind or a leaf’s natural October fall carried the pair to the ground.

My children’s-book-writer imagination pictures the little nymph, bug-eyed and excited, as it straddles a fluttering leaf. Wouldn’t that make a cute story? Ok, so maybe cute isn’t the best approach for this tale.

Still… wouldn’t kids love learning about baby bugs that make their own juice boxes?

Resources and a Related Kids’ Book

Here’s a fun article (where I stole the juice-box metaphor): Michigan insects in the garden – Week 3: Assassin Bugs. It’s from Michigan State University’s extension service.

This article, A Zealous Assassin: Pale Green Assassin Bug, Zelus Luridus is from the University of Maryland extension. The article includes a video of a wheel bug (a type of assassin bug) stalking and stabbing a caterpillar. There’s also a video of hatchling pale green assassin bug nymphs taking the sticky stuff from their egg cases.

Now, for a terrific kids’ book: I laughed out loud as I read The Bugliest Bug by Carol Diggory Shields, illustrated by Scott Nash.

This picture book for ages about 4 to 7 has suspense, rollicking rhyme, and insect info rolled into one. Perfectly suited to read aloud, it’s a well-crafted marriage of fact and fiction.

All kinds of insects gather to compete for the title of ‘Bugliest Bug.’ The story builds suspense as we wait to learn which insect wins the contest. The action heats up when the protagonist, an unassuming damselfly, begins to suspect the contest’s organizers—a gang of spiders—have ulterior motives.

Insect facts weave beautifully into the story. One concern of many reviewers is the illustrator’s choice to show insects with two arms and two legs instead of including six legs, as in real life. Even so, the art is fun and otherwise conveys the insects’ appearance. I feel that overall, the art works just fine. I highly recommend this book. It’s fun to read and a terrific way to encourage bug-inquisitiveness in very young kids.

Image Credits: Carol Doeringer.

10 thoughts on “Call CSI: It’s an Insect Murder Mystery”

  1. Ooh, I do love a good murder mystery! This one’s been masterfully solved, and I’d love to see it turned into a kids’ book. Onward!

  2. The Bug Murder Mystery! What a great book idea. Maybe even a graphic novel about lots of bugs who masquerade as assassins! Yeah, this is gross and fascinating at the same time. Great video and research, Carol.

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