a peek inside the fishbowl

28 May, 2020

Raising aliens (a.k.a. a pandemic science project you can do at home)

Posted by andrea tomkins in: Easy ways to make kids happy|Misc. life

If you follow me on Twitter you may recall a thread I posted last year about a praying mantis egg case I bought at Costco, and the results of said egg case. Well I bought one again this year and I realized I never wrote about it here on the blog. What has prompted me to do this now is an email from a friend who is incubating her own praying mantis babies and I thought it might be helpful to jot a few things down.

Praying mantises (manti?) are considered natural insect control. The eat a whole host of backyard bugs including aphids, beetles, flies, mosquitoes, moths, and caterpillars.

Mama mantis lays her eggs in a case (called an ootheca, which I’m trying to remember for future crossword or trivia purposes) which contains many eggs inside. The ootheca isn’t much to look at, to be honest. It looks like a brown and shrivelled golf ball and if I saw one in the wild I might just ignore it.

The instructions that come with the egg case say that the mantis babies therein will hatch in 1-8 weeks. That’s a long time, I know. I bet lots of people give up. Last year ours took just over a month to hatch. (I started May 22 and they hatched June 28.) Of course, you have the option to leave the egg case outdoors but you won’t get to see the babies because they disperse quickly. This is why we decided to do it indoors so we can see the little buggers before releasing them on our aphid-infested plants.

Here’s how we hatched praying mantis babies at home:

  • The egg case comes in a little mesh bag. We took a large glass jar, put some sticks inside it, and used a clothes pin to attach the mesh bag to a branch so it’s not touching the bottom of the jar.
  • We used an elastic band to attach a cloth across the mouth of the jar, because, air.
  • We put it on the window sill.
  • We used a mister to spritz a bit of water in the jar every day or so.

And then we waited. And waited.

This is what it looked like when they were born:

Cool eh? Baby mantises are basically miniature versions of adult mantises.

Newly hatched baby praying mantis

Some points to consider:

  • You will have no idea WHEN the eggs are about to hatch because the egg case looks the same the entire time. The babies just show up one day. (Consider taking bets.)
  • The NUMBER of babies will also be a surprise. Apparently you can have a few dozen or a few hundred.
  • We released them outside right away, which I think was a mistake. They are very small, and we had a rainstorm the next day. This time around we will wait a few days before releasing them, even though they might eat each other. Maybe the survivors will be a little tougher? (If you have kids, feel free to turn this part into a lesson on natural selection.)
  • You can keep a mantis in a closed aquarium. You just have to feed it appropriately-sized bugs.

You’ll feel like you’re in your own sci-fi film, with small predatory aliens that have cannibalistic tendencies. Bulging eyes on the side of triangular heads! Stick legs that bend in weird places!

It’s a face that only a mother could love.

Our neighbour found an adult mantis in her garden a few months after we released them and brought it over to show us. Mark managed to get it into a jar (honestly, I wouldn’t touch it with a ten foot pole). Here it is:

I’m not sure if our ootheca will produce any babies. Some reviewers on the Costco site said they got duds. But that’s nature, right? We will just have to wait and see.

3 Responses to "Raising aliens (a.k.a. a pandemic science project you can do at home)"

1 | Jennifer

June 1st, 2020 at 2:24 pm


That is really cool.
I was wondering if you kept it outdoors? There is research on hatching monarchs indoors that it compromises them. They need the sun and the stars, they’ve found.

2 | andrea tomkins

June 2nd, 2020 at 11:52 am


Nope. The jar is on our window sill! It’s getting the same dark/light cycle they’d have if they were on the outdoor side of the window. :)

3 | a peek inside the fishbowl » Blog Archive Pass the cigars, the babies are here! - a peek inside the fishbowl

June 9th, 2020 at 12:30 pm


[…] thought I should share an update to this post. Our praying mantis babies actually hatched soon after I wrote it. It was all very exciting and […]

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My name is Andrea and I live in the Westboro area of Ottawa with my husband Mark and our dog Piper who is kind of a big deal on Instagram. We also have two human offspring: Emma (24) and Sarah (22). During the day I work as a writer at the Royal Ottawa Mental Health Centre. I am a longtime Ottawa blogger and I've occupied this little corner of the WWW since 1999. The Fishbowl is my whiteboard, water cooler, and journal, all rolled into one. I'm passionate about healthy living, arts and culture, travel, great gear, good food, and sharing the best of Ottawa. I also love vegetables, photography, gadgets, and great design.

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