How does a mantis hunt?

The strike has two phases

A mantis's front-leg strike is split into an approach phase, in which the front legs are extended toward the prey, and a swing phase, in which the leg segments snap open quickly and the tibia folds shut around the prey. A 1990 study that filmed the Chinese mantis split it into these two phases, and later studies use the same split.

The femur and tibia of the front legs are lined with movable and fixed spines. When the two segments fold together, the spines interlock so caught prey can't slip out.

How fast is it?

In 2016 a US team filmed ghost mantis nymphs' strikes at 1,000 frames per second. The approach phase took about 21 milliseconds on average (a millisecond is a thousandth of a second), and the swing phase about 9 milliseconds. The swing took about the same time each time, and a bit longer the farther away the prey was.

But mantis strikes are not always this fast. In 2020 a UK team analyzed 96 strikes by 8 Madagascar marbled mantises and found total strike times of 60 to 290 milliseconds (median 100 milliseconds). The slower the prey moved, the slower the strike, and sometimes it paused midway. Yet the success rate had nothing to do with strike speed. The mantis adjusts its strike speed to the speed of its prey.

How they aim

Most mantises are ambush hunters that wait in one place for prey to come. When they notice movement at the edge of their vision, they snap the head around to put the image of the prey on the high-resolution part in the middle of the compound eye. If the prey is slow, the head follows smoothly; if it's fast, the head-turning repeats.

To judge the distance to a still object, a mantis sways its body from side to side. This uses the principle that when you move, near objects seem to shift a lot and far objects a little. At the moment of the strike, it also uses stereo vision with both eyes together; that story is in the 3D glasses experiment.

How often the male gets eaten in mating

The claim that "a female mantis always eats the male after mating" is wrong. Here are the rates measured in the wild.

• European mantis: In a survey of a wild population, the female ate the male in 31% of matings (Lawrence 1992).
• Chinese mantis: Eating of the male during mating was reported at under 10% (Hurd et al. 1994).

Hunger makes a big difference. In an experiment on an Australian mantis species, starved females ate the male in about 89% of encounters, while well-fed females never did. Females that ate the male increased their egg case weight by up to about 40%. But 89% is a figure for starved females in the lab and shouldn't be used as a rate in the wild.

It has been pointed out that the impression that cannibalism always happens came largely from early observations in which a hungry female and a male were put together in a small container. The observation by the French entomologist Fabre, who recorded one female eating several males in turn, was also made in an enclosure.

Records of catching birds and fish

In 2017 researchers gathered cases worldwide of mantises eating small birds. There were 147 cases from every continent except Antarctica, across 13 countries, with 12 mantis species catching 24 bird species. Most of the birds eaten were hummingbirds, and over 70% of the records came from the US, often around garden hummingbird feeders. Because the number comes from several decades of records, it doesn't mean mantises commonly hunt birds.

In 2018, in a rooftop garden pond in India, a male mantis (Hierodula tenuidentata) was observed visiting for five days in a row and eating 9 guppies. It is the first scientific record of a mantis catching fish.

Research in this article