|
The
Chinese mantid is a
large species. Some individuals reach
3½
inches in length. They are variable in
color, from brown to green, but most Arkansas specimens tend to be mostly brown, with
green
stripes along the leading edge of the front wing. The
species has only one generation per year,
and females die after producing eggs in the fall. As
many as 200 eggs are embedded in a
Styrofoam-like egg case called an ootheca. Well-fed
females can produce four to six oothecae under
ideal laboratory
conditions, but in their American range, they rarely have time to
produce more
than one or two before killing frosts arrive. The
eggs overwinter and hatch the following spring, with
most eggs
hatching simultaneously. However, eggs
kept indoors will hatch, even without being subjected to a period of
cold
temperatures. Unless the nymphs are
separated or well supplied with food, they will disappear one by one
through
cannibalism.
The Chinese mantid
is
widespread, and its ecology has been well studied.
It can be found in a wide range of open
habitats among many types of vegetation. It
is native to most of temperate Asia, and it has attained a widespread but
patchy distribution in the
eastern United States. It is
believed to have been accidentally
introduced into the United States with imported plants around 1896, at
which time it
was found in Philadelphia. A nearby
nursery was at that time receiving plants for all parts of the world. In the past century it has spread to form a
contiguous range from southeastern New York to northern Georgia and from the Atlantic coast to the Mississippi River valley. Occasionally,
individuals are found outside
this distribution, even in areas where they cannot survive the winters. Females do not fly, but males may fly short
distances. Individuals do not readily
travel
more than a few feet from their place of birth under their own power,
yet the
species has spread across the United States in the past century.
Dispersal has been mainly through human agency, with eggs
transported on
vehicles and nursery stock and sold through the mail for biological
control of
insect pests.
Only a few
individuals survive from egg to reproducing adult.
Most mortality occurs in the early nymphal
stages from starvation, predation, and desiccation.
Eggs that hatch too early produce nymphs at a
time when prey are scarce. Nymphs can
consume pollen to prolong their survival until suitable prey can be
found, but
still only less than ten percent of individuals survive to adulthood. The rate of development is highly dependent
on temperature and season length, which determine whether or not the
individual
will mature and reproduce before a killing frost. To
a lesser extent, rate of development is
dependent on food supply, but food limitation reduces fecundity.
Chinese mantids are
opportunistic, generalist predators, taking virtually anything they can
overpower, mostly other insects. In the
entomological literature, there are at least two believable reports of
Chinese
mantids capturing and consuming vertebrates in captivity (soft-shelled
turtle)
and in the more natural setting of a flower garden (whitefooted
mouse).
In the latter case, a 3.0 to 3.5 inch mouse was captured by a mantid,
which
then began to consume the living mouse, starting at the nose and
working back,
eating hair, bones, and other tissues along the way. In
the ornithological literature there are a
least two reports of mantids, presumably Chinese mantids, capturing
hummingbirds. Chinese
mantids are well
camouflaged and probably invisible to visually-oriented prey.
Studies
have shown that sexual
behavior in the male can be enhanced by decapitation, and the general
public
has become fascinated with the concept of sexual cannibalism in mantids. It is true that females sometimes consume
their mates, but how frequently this happens is unknown.
Mate consumption probably allows the female
to mature eggs late in the season when other prey are scarce. Females that perch on asters and goldenrods
have flower-loving insects at their disposal late in the season, and
therefore
they are at a reproductive advantage over individuals perched elsewhere.
|