When Young Praying Mantises Emerge

The marvelous month of May has arrived in Eliza Howell Park and it is bringing out nature lovers. The forest floor is alive with small ephemeral flowers and some of the elusive colorful warblers are pausing briefly on their 3000-mile annual spring migration from Central America to the North Woods.

One of the marvels of May in the park is observed by very few people — the emergence of the year’s Praying Mantises. It happens quickly and the timing is weather-dependant, so not fully predictable. Someone in the right spot at the right time (probably late in May) can observe the fascinating phenomenon of a hundred or more young mantises crawling out of and away from an egg case in which they spent the last 8 months.

Scattered in the park, mostly near the meadow wildflower field, are a number of  egg cases (oothecae) of the Chinese Praying Mantis, attached to shrubs, limbs of small trees, flower stems, and vines, usually 1 to 4 feet from the ground. This photo is from this week.

Later this month, tiny new mantises will emerge en masse from the cases that survived the winter intact and healthy. Last year, a colleague and I witnessed  such events most clearly May 21 to May 23.

Praying Mantis young are very small. The egg case is usully only about an inch high and contains dozens to hundreds. Though tiny, they emerge fully developed, except that they lack wings. They head away immediately and begin to search for other insects to eat.

Praying Mantises do not survive the winter as adults. The new ones that energe in the spring die in the fall, after mating and egg laying. I usually don’t see them until some time in August, by which time they are fully grown and are preying upon the insects attracted to the summer flowers. The Chinese Praying Mantis is often over three inches long at maturity

After mating, females lay eggs (making the cases at the same time). In Eliza Howell, this usually occurs in September. This egg case was new when this picture was taken in mid September.

From September until May, through the long cold winter, the Praying Mantis population is contained in these insulated oothecae

By far the largest number of Praying Mantises in Eliza Howell Park are the Chinese species — and my observations above all apply to it. This year, though, we found a few cases that are distinct enough (and placed differently enough) to be a different species. It is probably European Praying Mantis, a little smaller species also found in Michigan.

As it gets warmer, we will try to keep an eye on these few cases as well. I have no experience with what they look like as the young emerge. With watching — and with sone luck — perhaps it will happen this year.

The weather has been cool this spring, so I do not expect mantis emergence within the next few days, but I hope I am there whenever it happens. It is a “Wow!” experience.

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