Tag Archives: butterfly

Identifying mantid egg cases in Pennsylvania

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Below are photographs and descriptions of egg cases of the (native) Carolina mantis, the European (=praying) mantis, the Chinese mantis, and the narrow-winged mantis.

Carolina mantid (Stagmomantis carolina)

Carolina mantids (the only native species in my area) form relatively smooth, teardrop-shaped oothecae with a central portion that is lightly colored. Often found on tree trunks, rocks, and buildings.

Egg case of Carolina mantid (Stagmomantis carolina)

European mantis (Mantis religiosa)

These oothecae are somewhat similar to the Carolina mantis’ but lack the alternating bands of color. Another common name for the European mantis is the praying mantis.

Egg case of European mantis (Mantis religiosa)

Chinese mantid (Tenodera sinensis)

Chinese mantid oothecae are typically roundish, roughly textured, and uniform in color. Introduced from Asia, as you probably guessed.

Egg case of Chinese mantid (Tenodera sinensis)

Narrow-winged mantid (Tenodera angustipennis)

Narrow-winged mantid oothecae are usually rather elongate. They are also seem to have red streaks, though the color seems to be most noticeable after they age a few months. Introduced from Asia, too.

Egg case of narrow-winged mantid (Tenodera angustipennis)

More ID help

For an excellent overview of all of these species, please see the Cape May Wildlife Guide’s page on mantids. Please also see the excellent guide by Paweł Pieluszyński of the Brooklyn Bridge Park, especially because it includes an ootheca of the Asian jumping mantis (Statilia maculata) that is probably lurking undiscovered in Pennsylvania. If you need help identifying an ootheca, I highly recommend posting a photograph on iNaturalist. Not only will you get an answer from the iNaturalist community within a day or two, your submission helps scientists track the spread of invasive species.

What should you do with the non-native oothecae?

Invasive mantids eat butterflies, native bees, honey bees, small birds, and also the native mantid, so when you find egg cases, dispose of them. Here are some suggestions on how to do that:

  • Put them in a freezer for a week
  • Step on them
  • Give them to a neighbor who has chickens
  • Give them to local bird rehabilitation centers
  • Give them to a neighbor who has a pet tarantula, snake, lizard, or fish

Whatever you do, please not just relocate oothecae to some nearby field — that just transfers the problem to someplace where you can’t see the problem.

But aren’t mantids great for pest control?

Although it’s true that young mantids consume a lot of insects, some of which might be pests, when mantids are fully grown they tend to camp out on flowers and wait for large butterflies and even small birds. Mantids are, of course, excellent for controlling butterflies and hummingbirds in case you happen to hate those animals.

Monarch butterfly captured by a Chinese mantid (Tenodera sinensi
Monarch butterfly captured by a Chinese mantid (Tenodera sinensis).

Chinese mantids eat monarch butterflies

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This post is a PSA for anyone keen on helping monarchs: if you find Chinese mantids (Tenodera sinensis) in your yard, kill them. As proof, below is a photograph of one that had just snagged a monarch visiting my swamp milkweed. The monarch is fine, by the way. After I intervened she flew off, then came back within seconds and resumed ovipositing.

Monarch butterfly captured by a Chinese mantid (Tenodera sinensi

But unless you’re observing your milkweed patch obsessively, you’ll probably never catch a Chinese mantid in the act. But you can infer their presence by piles of monarch wings (i.e., no body attached). No other animal does this to monarchs.

Monarch butterfly wings left by Chinese mantid predation

And caterpillars are just as susceptible. Here’s a Chinese mantid I interrupted just as it was about to strike:

At base of milkweeds was a pile of monarch butterfly wins. Swarthmore, PA.

Chinese mantis can be easily distinguished from any of the native mantids by the presence of a yellow dot in between the forelegs.

Chinese mantis (Tenodera sinensis)

If you find an ootheca (egg case) of this species, crush it. The oothecae have an irregular, messy surface that looks like a blob of brown, poorly-applied insulating foam. Oothecae of the native Carolina mantis are much smoother and streamlined (see, “Identifying mantid egg cases in Pennsylvania“).

First-instar nymph of Chinese mantis (Tenodera sinensis) on ootheca

If you’re like most people (including myself), you grew up believing that mantids are a pesticide-free way of reducing garden pests. How could thousands of web sites be wrong?? The truth is, however, that Chinese mantids are so large that they tend to only eat large insects, and that usually means mainly butterflies, not aphids or other species that are tiny. So if you hate butterflies, by all means encourage Chinese mantids in your yard. But if you like butterflies in your garden, kill the Chinese mantids. And don’t just relocate them, even though that seems like the friendly, eco, green, peace-loving thing to do. Moving introduced, invasive species to another location simply facilitates further spread.

FYI, Chinese mantids also eat hummingbirds, plus other birds that are even bigger. The authors of that linked paper conclude,

“Our compilation suggests that praying mantises frequently prey on hummingbirds in gardens in North America; therefore, we suggest caution in use of large-sized mantids, particularly non-native mantids, in gardens for insect pest control.”

Italics mine.