Praying Mantis Oothecas (What Time is it in Nature)

This week’s post is brought to you by Julie Hall, citizen science educator for the Museum.  Julie coordinates our Dragonfly Detectives program and does a variety of other programs and activities at Prairie Ridge.  Thanks Julie!

On a recent walk at Prairie Ridge Ecostation on a beautiful sunny winter day, I started noticing how many praying mantis egg cases, or oothecae, there were on small branches not only out in the middle of the prairie, but also in the forest edges. Reaching 37 on my count of egg cases, I got really curious and started to formulate questions. How many babies come out of these cases? When will they emerge? Is there more than one species of mantid? I broke open the bug guides and learned a lot!

The ootheca most commonly found at Prairie Ridge looks about the size of a ping-pong ball, made of a foam-like material which hardens to prevent water loss:

Chinese Mantid egg case

This egg case is made by a non-native species, the Chinese Mantis.   This species has been found in the US since at least 1895. If the egg case has the look of tiny horizontal blinds, then the approximate 200 inhabitants have hatched and moved out:

Chinese Mantids hatching. Photo by Julie Hall.

The other ootheca I found is less common and smaller in size with a more elongated shape:

Carolina Mantid egg case

This one is made by a native species, the Carolina Mantis.

A third species of mantid has been found at Prairie Ridge, the Brunner’s Stick Mantis. Its ootheca is similar to the Carolina Mantis case but has a thorn-like spike on one end.

For best luck in an ootheca search, stick to open sunny areas such as fields and roadsides where there is no mowing. Mantids are attracted to sunny areas because they can move better when they are warm, so this is where they end up laying eggs.

Now it may seem like a good idea to collect or purchase oothecae to place in your garden for pest control, but don’t do it. Mantids are generalist predators, so they will eat beneficial bugs right along with the pests! If you go around collecting oothecae and relocating them to your garden, you may end up losing all of your butterflies for the year. (Don’t ask me how I know!)

Winter is best for ootheca viewing at Prairie Ridge, when bare twigs abound. The next time you are out on a nature jaunt, keep an eye out for these fairly conspicuous eggs masses and see how many you can find! Another tip: warm temperatures will initiate hatching… so don’t bring an ootheca inside your house unless you know it’s tiny inhabitants have come out.  Otherwise you might end up with hundreds of hungry babies scattered about!

What Time is it in Nature is a weekly feature highlighting the current plants, animals, and other wildlife at the Museum’s public outdoor facility, Prairie Ridge Ecostation.  Find out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive.