Garden Tips: Praying mantids eat bad — and good — insects

Not long ago, a local gentleman called me because he had rescued several mantid egg cases that were laying in tires that were being hauled away. He had heard that mantids were beneficial and wanted to protect the egg cases until they hatched. I am not an entomologist, so my knowledge of mantids is not vast, but I have learned a little about them because they are frequently encountered in gardens.

The mantid that most often catches our attention is the European mantid (Mantis religiosa). It is native to Europe, Asia and Africa, and reportedly entered North America on nursery plants around 1899. It prospered and can be found throughout the U.S. and Canada.

Some gardeners even buy mantid egg cases because the mantids are touted as beneficial insects. This is debatable. They do feed on other insects, but they do not discriminate between bad insects and good ones, like butterflies and bees. However, they can certainly be appreciated as an insect curiosity.

The European mantids are not usually noticed in the garden early in the season, when they are small, but by the end of summer, their elongated bodies have grown to a length of 3 or 4 inches, and they are easily seen.

One thing that makes the mantid so fascinating is its unusual appearance. It looks a little like an insect that works out because it has large, well built spiny forelegs. The praying moniker comes from its forelegs that appear bent in prayer before they are used to quickly reach out and snatch prey.

Along with its muscular forelegs and elongated body, is an alienlike triangular head with large bulging compound eyes and a big, strong mouth for biting off the heads of prey. The mantid is also able to rotate its head 180 degrees, allowing it to scan a wide area for potential victims.

Another interesting trait of mantids is their ability to change color to blend in with their background. Their body can be bright green, brown, reddish brown or gray depending on the surroundings. This ability allows them to camouflage themselves and let their unsuspecting prey come to them.

Did you know that mantids are sexually cannibalistic? The females are known to bite off the heads of a male during mating. You can find videos of this phenomena online, but scientists say that this behavior occurs less than 30 percent of time when mantids mate in the wild. They speculate that it occurs when the female is hungry and needs nutrition for egg laying. Speaking of cannibalistic behavior, nymph or “baby mantids” eat each other if they do not have access to other food immediately upon hatching.

After mating, female mantids lay up to several hundred eggs in cream colored foamy egg masses that look somewhat like a styrofoam packing “peanuts” when they dry. The egg cases are typically attached to rocks, fence boards, tree trunks and branches, and the walls of structures. The adults do not survive the cold temperatures of winter, but in the spring their offspring hatch from the egg cases.

By the way, there is a native mantid in Eastern Washington. It is Litaneutria minor or the agile ground mantid. This ground-dweller is only about an inch and a half long and dark gray to tan in color, making it much less noticeable than the alien European mantid.

This story was originally published May 22, 2016 at 7:32 AM with the headline "Garden Tips: Praying mantids eat bad — and good — insects."