Purdue Extension Service

Vanderburgh County, Indiana

The Perils of Beneficial Insects

by Larry Caplan, Extension Horticulture Educator, Vanderburgh County, IN

For the Evansville Courier and Press, May 7, 2000

So you think that beneficial insects are the answer to all your pest problems? Then gather 'round, my children, and hear the twisted tale of: "The Praying Mantises That Took Over Evansville."

Earlier this spring, while pruning some shrubs, I found a couple of praying mantis egg sacs. I figured they would make excellent additions to my insect appreciation lesson. So, I innocently brought the egg sacs to my office, and placed them in an insect collection box.

I eagerly awaited their hatching. And awaited. And awaited some more. After a couple of weeks, I needed the bug box for one of my other critters. I put the mantis egg cases on my desk, and didn't think any more about them. Until Friday morning. . . .

I came into my office, and took a call from a farmer. As I tried to speak intelligently about pasture improvement, I suddenly felt like I was being watched. I glanced down at my notepad, and noticed a tiny praying mantis staring at me. Movement to the left caught my eye, where I saw another baby mantis crawl out from under a pamphlet. Then another one scurried out from behind the phone. My mouth went dry as I noticed two more on my computer, and four or five on the wall.

I slammed down the phone, grabbed my bug box, and proceeded to hold my first "mantis roundup". (By the way, if you are ever in a similar situation, take some advice from someone who learned the hard way. Baby praying mantises are too delicate to actually be picked up. You need to slide a piece of paper under them, and carry them to your collection box.)

At this point, one of my Master Gardeners came in. He took one look at me holding a plastic box with dozens of praying mantises crawling in, out, and over the container, and sprang into action. In about an hour, we had corralled somewhere over 40 or 50 baby praying mantises.

"What are you going to do now?" my Master Gardener asked. To be truthful, I hadn't thought that far ahead. I supposed I could let them go outside, but I really wanted to raise them for teaching purposes. Then I remembered that I'd seen a company's catalog that sold kits for raising praying mantises in a classroom. I grabbed the phone and dialed frantically.

"I have a praying mantis emergency!" I shouted to the startled sales lady. "I need your praying mantis nursery kit, and I need it today!"

"Of course, sir" she replied after a moment's hesitation. "That kit comes with 30 test tubes to keep the praying mantises separate, a supply of wingless fruit flies to feed them, and two praying mantis egg sacs for you to hatch in your classroom."

"Can you ship that to me without the eggs?" I asked despairingly, as 50 baby mantises glared at me from their plastic prison.

"I'm not sure," she replied doubtfully. "I'll have to check with my supervisor. I can call you back later today . . . ."

"Never mind!" I cried. "I can't wait! Just ship me what you've got overnight!"

Saturday morning, my wife took the package from the UPS man. She took one look inside, and pushed it at me. "Most women get flowers from their husbands," she declared with disgust. "I get bugs!"

Following the instructions that came with the kit, it only took me a couple of hours to put one praying mantis and three wingless fruit flies in each of the test tubes. I figured the escaped fruit flies would sooner or later be caught by the escaped praying mantises, making for a balanced ecosystem in my kitchen.

I now have the entire menagerie sitting on my desk. As long as I remember to feed them wingless fruit flies every other day, they should be OK. I'm not too sure what to do with the egg cases in the refrigerator. And I still have the uncomfortable feeling of being watched.

For more information on the correct use of beneficial insects, contact the Purdue Extension Service at (812) 435-5287.