Preying mantis egg cases

[MG gal 5]

When doing some pruning I found 3 preying mantis egg cases.  I have them in a large bug barn on the back porch.  Should I take the egg cases into the garden and leave them?  I would really like to see them hatch and share with the grandkids.

 

Any ideas?  About when will they hatch?

[Janet Macunovich 32]

Our vote's for letting it hatch outdoors. Put one of the cases in a bag/box you make out of window screen and leave it flagged where you and the kids can find it. Or put it in a terrarium cool place indoors so you can put the little mantids back outdoors right away. We've had them hatch indoors and then had to round them up and put them out. It's a crazy thing. In the case of Mantis Claus hatch, they hatched way too early so to save them we had to find a year round greenhouse looking for predators, round them up and transport them.)

When do they hatch on their own outdoors? Hmm. Seems like it's middle-late May. We've noted a couple of egg cases in our garden (not enclosed) and we might notice when they're gone but probably will miss the exact day (Murphy's Law applied to gardens). If you pay daily attention will you let us know? Then we can relate it to growing degree days since the date will vary year-to-year with accumulated heat.

[carolm 1]

Insect hatches are usually tied pretty closely to growing degree days.  MSU might have some info as to when mantid eggs hatch, and the number of  growing degree days we've accumulated this season.  (I've recorded around 90 so far but that's just in my yard).

[msk929 0]

Quite awhile ago, when my kids were small, we ordered egg cases and put one of them in an aquarium with a screen top. Spring vacation happened and when we returned, we found a few survivors clinging to the screen and many bodies below.  There was nothing to eat when they hatched so, they ate each other!!.  Hence the good advice above to let them loose as soon as they hatch!1

[Janet Macunovich 32]

Okay it looks like I won't be able to find growing degree days info for praying mantids in any short order so can't be very precise with when the eggs in a case should hatch. ("Eclose" is the technical term for what insect eggs do, and can be a handy term for doign searches if what you want is scientific data/reports/journals.) Bu t I have found that the eggs do seem to need a 3 month diapause at about 40°F (winter rest) and then steadily increasing warmth and moisture (so, not indoor hot air) until the temperature reaches about 86°F. That sounds like early June most years but May some years.