Invertebrates
Chinese Mantis
Tenodera sinensis · also called Chinese praying mantis
The big green mantis on the garden fence in most of the eastern United States is not a native. It is the Chinese mantis, an East Asian insect that arrived by accident in the 1890s, grew into the largest mantis on the continent, and is now common enough that garden centres sell its egg cases by the thousand.
Overview
Tenodera sinensis is native to East Asia and was introduced to North America around 1896. Females reach 10–11 cm, making it the largest mantis in North America, and it has spread across most of the eastern and central US. It is a sit-and-wait ambush predator of insects.
The egg case, and the hummingbird problem
The female glues a walnut-sized foam egg case to a stem, holding 100–300 eggs. These are sold as natural pest control, though the hatchlings mostly eat each other and the adults take pollinators as readily as pests. Large females also ambush hummingbirds at nectar feeders — a worldwide review found around 150 such cases, most of them this species.
Other tricks
The female sometimes eats the male during mating, head first; a headless male can still finish. And a single bat-detecting ear on its underside triggers an evasive dive in night flight.
Status
Least Concern and abundant. Its spread is watched because it competes with and eats native mantises like the smaller Carolina mantis.
Chinese Mantis: common questions
Do praying mantis egg cases sold for the garden actually help with pests?
Not as much as the packaging suggests. A Chinese mantis egg case releases 100 to 300 tiny nymphs at once, and in the first days most of them eat each other, so only a handful survive in a given area. Those that do are indiscriminate ambush predators that will take a ladybird, a bee, a butterfly, or a parasitic wasp just as readily as an aphid-eating hoverfly or a caterpillar, so they remove beneficial insects along with pests. There is little evidence that adding mantis egg cases measurably reduces garden pest damage, and releasing a non-native species is generally discouraged. Mantises are fascinating to have around, but as pest control they are marketing rather than science.
Can a mantis really catch a hummingbird?
A large one can, and it happens more often than people expect. Chinese mantis females, which can exceed 10 centimetres, position themselves on flowering plants and, notoriously, on the plastic perches and feeding ports of hummingbird nectar feeders, and strike at a hovering or perched hummingbird with the spined raptorial forelegs, pinning it. The mantis then feeds on the bird, often starting with the head or the flight muscles. A global compilation of records found roughly 150 cases of mantises capturing small birds, the majority involving the introduced Chinese and European mantises at feeders in the United States. Placing feeders away from dense vegetation and checking for mantises reduces the risk.
Is the Chinese mantis dangerous to people?
No. It has no venom and no sting, and although the front legs are lined with sharp spines for gripping prey, a mantis cannot break human skin with more than a pinprick, and its bite is negligible. A cornered mantis will rear up, spread its wings, and strike, which is startling from a hand-sized insect but harmless. The main reason to handle one gently, if at all, is for the mantis's sake, since its long legs and soft abdomen are easily injured.
How is the Chinese mantis different from the native mantises?
In the eastern United States the main native mantis is the Carolina mantis, which is smaller, at 5 to 6 centimetres, more grey or mottled, and has shorter wings that do not reach the tip of the abdomen in the female. The Chinese mantis is much larger, greener or tan, with full-length wings and the diagnostic yellow spot between the front legs and green wing stripe. The European mantis, also introduced, is intermediate in size and has a distinctive black-ringed spot on the inside of each front leg. Where the Chinese mantis is common, Carolina mantis numbers tend to be lower, partly through competition and partly because the larger species eats the smaller one.