Look closerInsects
Mantis egg cases on winter twigs
When: November to March
A mantis lays one hard foam case in autumn and then dies. The case sits out all winter on a twig or a fence post looking like a squirt of insulation, with dozens to hundreds of eggs inside waiting for spring.
Why this time of year
They are laid in the fall and hatch in spring, so the whole findable window is winter, and it is the one season the leaves are off and you can actually see them. The adults are already dead; the case is the entire next generation.
How to notice it
- Scan bare twigs, stiff plant stems, fence posts and the sides of buildings at about waist to head height.
- You are looking for a light brown lump about an inch and a half across with the texture of foam insulation.
- Two shapes: the common Chinese mantis case is bigger and puffier; the native Carolina mantis case is smaller and flatter.
- Leave it where it is. Bringing one indoors hatches hundreds of mantises into a warm house weeks early.
Try this with kids: Find a foam lump on a bare twig. How many mantises do you think are inside it?
an ootheca is the hardened foam case an insect lays its eggs in
Safety
- Look, do not collect. A case taken into a warm room hatches early and the nymphs have nothing to eat.
Sources
- extension.illinois.eduIllinois Extension: adult females lay their ootheca in fall and it quickly hardens for winter, the mother dying shortly after; cases are light brown, about 1.5 inches wide and look like foam insulation, containing dozens or hundreds of eggs; Chinese mantises attach them to twigs, stems, rocks, or the sides of buildings and fence posts, anywhere somewhat vertical; Chinese mantis cases are larger and foam-like while Carolina mantis cases are smaller and flatter; nymphs emerge the following spring, sometimes eating each other; adults die out in late fall and early winter, leaving only the egg cases
In the guide for November, December, January, February, March