Growth and Development of Praying Mantises

Praying mantises, or mantids, have always fascinated me. They start their

life as one of hundreds of eggs packed together in an egg case which is

protected with bird-repellant foam. In the end, when they’re full grown,

birds are still enemies, but little else is. They must endure a summer

of peril first…

After hatching, once the tiny mantids’ exoskeletons have hardened, they

need to take care of two things: finding food and taking shelter from

enemies. The first food of these young hunters is small insects such as

mosquitoes and gnats. They have no problem with eating each other.

Arthur V. Evans (The Field Guide to Insects and Spiders of North America)

says, “If appropriate food is not readily available, they will not hesitate to

eat their siblings.” At the same time, the mantids must find shelter from

birds and spiders. Habitats vary some from species to species, but tall grass

or low bushes are the most common places to find a mantid.

Evading predators is something they must do. From the moment they

emerge from the egg case they are in danger. Birds, spiders, and their own

siblings are everywhere. Fortunately, they are very agile climbers and

jumpers, taking quick flight at the first sign of danger. A shadow moving

across them, a grass blade quivering, or a twig moving the wrong way, and

they make a dash for it, leaping and climbing to a new hiding place.

They can hold still for hours to escape detection, or sway gently in the

breeze with the vegetation. Their pale brown to gray color also helps by

blending in with twigs.

Mantids develop by gradual metamorphosis. This means they go through

three distinct life stages: egg, larva, adult. They live in the same general

habitat as larva as they do when adults.

To grow, they need to go through a process called molting. This is because

their hard exoskeleton will only allow limited growth. It needs to be split off

to allow for a new, larger one. They will go through six to nine molts before

becoming adults.

When a young mantid is going to molt, it first finds a thick stem or some

other support. From this it hangs upside down, sometimes for hours. Then a

split in the exoskeleton appears on the thorax. The mantid will twist and

sway, trying to elongate it. Once the split runs lengthwise along the whole

thorax, the young mantid will begin to struggle free of the old skin. First out

comes the thorax, than the forelegs and head. Next it pulls each middle and

rear leg out. During this process most of the abdomen is freed also. Now the

mantid hangs upside down for a bit, the tip of its abdomen still in the old

exoskeleton. After a brief rest, the young mantid will free itself and continue

to hang from its support until the soft, pale, new skin hardens and darkens.

During molting, mantids must be careful not to fall. If they fall, and are

still in the old skin, they will not be able to free themselves and die. If they

fall after a molt, before the exoskeleton hardens, their legs could be bent,

taking several molts to straiten out again.

As they grow, the mantids will develop wings and a hearing organ. This

“ear” begins to form in the third molt. It is located on the underside of the

thorax, near the base of the forelegs. It is completely developed by the sixth

molt, and probably helps them detect approaching predators. The wings

develop in two pairs of cases, or “wing pads,” at the base of the thorax. They

are fully developed by the last molt when they are pulled free of the cases

and unfolded to dry and harden.

Finally, after a dangerous summer, the tiny mantids who survived are now

impressive hunters. They range in size from 3/8 of an inch to 5 7/8 of an

inch. They can fly, and are masters of camouflage. After a summer of

growth, they can take on the biggest of insects, from large moths to cicadas.

They are one of God’s most impressive insects!