This is a follow-up to the posting on September 13 this year – “Praying Mantis Egg Laying.”
Adult Praying Mantises do not live beyond the fall; the next generation is in the egg cases and will emerge in the spring. They will emerge if all goes well. Since September, I have been checking on egg cases in Eliza Howell Park.
My observations began on September 5, when I watched two different females lay their eggs. This is what the fresh new egg cases looked like then.
That same day, I noticed a pair mating so was confident that those two egg cases would not be the only ones this year.
In the weeks that followed, I many times walked the narrow path through the field of wild flowers and small shrubs/trees. I gradually saw more and more egg cases, especially when they became easier to see after the leaves dropped. These five were found in early November.
As of now, I have located 11 different egg cases visible from that path. Almost all of them are on the small trees (buckthorn, for the most part) growing in the field. Since each egg case probably has dozens and dozens of eggs, 11 cases would suggest a large number of little mantises emerging in the spring. If all goes well.
Some of the birds that spend the winter in the park are insect eaters, birds that often seek insect eggs and larvae. Praying Mantis eggs, though protected in the oothecal, are vulnerable to birds with beaks that probe.
Recently, I have been seeing evidence of predation.
Of the 11 egg cases I am aware of, 6 have been opened like this. And it is only November. The number of Praying Mantises estimated to emerge in the spring in Eliza Howell is decreasing rapidly.
While I have not directly observed this, I suspect that Downy Woodpeckers are responsible for invading these egg cases. Insect eggs are a part of their diet and they frequently forage on small trees and on plant stalks.
Photo by Margaret Weber
Another threat to the survival through the winter is the weather. One of the eggs cases is on a goldenrod, a large perennial that typically does not stay standing all winter. Last week, during the first snowfall of the year, it was bent low by the heavy snow, but it came right back up when the snow melted. The first picture below is from November 9; the second from November 10.
The stem will get weaker as the season – and the snow — continues. I do not know how well developing Praying Mantises are likely to do when an egg case ends up on the ground, but there is a reason why they are placed off the ground when the eggs are laid.
We know that only a very tiny percentage of acorns sprout. In July, I reported that very few, if any, of the toad eggs laid in the breeding pond left the pond as toadlets this year. It should not be a surprise if only a small percentage of Praying Mantis eggs laid this fall will result in live mantises in the spring of 2019.