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
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!