The Walking Stick-Insects (Phasmida) (Phasmatoidea,
Phasmatidae)
Introduction
Stick Insects or Phasmids (Phasmatoidea,
Phasmatidae) encompass about 2,700 known Insect species. With their long
bodies that give them a twig-like appearance, Phasmids are almost invisible
among the leaves of trees. When They are disturbed, Phasmids will lay
motionless for hours pretending to be a stick. Sometimes, They will sway to
mimic a twig blowing in the wind.
To avoid being eaten,
Phasmids have many unique defenses. Although Most rely on passive camouflage
to avoid predators, many large Phasmids have large spines on their hind legs
for self-defense. Other Phasmids will discourage their attackers by
regurgitating food at them or by squirting them with poison. American Walking
Stick (Anisomorpha bupestiordes) sprays his intruder with a chemical
spray that causes blindness.
Female Phasmids can
reproduce without mating. Some populations consist entirely of mature Females
and their Offspring. The Young are identical to their Mother. Sometimes Mother
Phasmid will search for a rare Male to mate with. She will either find Him
with his Friends or will attract Him by emitting a seductive scent.
Unlike other Insects,
many people like to have Phasmids as pets. Usually all They require is
blackberry leaves and water to thrive. However, They do prefer to have their
leaves in their cages lightly misted.
Phasmids teach about
having as many choices as possible. For example, people call Them by many
names--Walking Stick, Stick Insect, or Stick Bug. Female Phasmids can
reproduce with or without a mate. Phasmids defend Themselves in various ways.
Some simply become still, while Others will squirt a poison. In life, it is
important to have many options available to you.
Ecology
Stick-Insect eggs
come in 2 main forms depending on whether they are dropped on the ground or
placed in some less accessible spot. Those that are just dropped to the ground
have a relatively large 'capitulum' this generally contains lipids and other
substances attractive to ants, the ants take the eggs back to their nests, cut
off the capitulum and feed it to their brood, the rest of the egg is then
thrown into a garbage dump. The Stick-Insect eggs gain protection from birds
and many other predators by being in the ant nest, and hatch quite happily
inside the nest or buried in the garbage. In some species of Stick-Insect the
newly hatched nymphs are 'ant mimics' i.e. Extatosoma tiaratum. This
whole process is a remarkable example of plant mimicry on behalf of the
Stick-Insects as many plants in similar habitats attach food bodies called 'eliasomes'
to their seeds in order that ants should take them back to their nests.
It is known that
seeds that germinate inside ants nests tend to grow stronger and produce more
seeds themselves than seeds of the same plant that germinate away from ants
nests. Apart from protection from predators and parasites both eggs and seeds
in ants nests are offered some degree of dispersal as well as some protection
from fire. Other species of Stick-Insect lay their eggs in the soil (Aretaon
Asperrimus), into hollow parts of plants (Graeffea crouanii), or
glue them to parts of the plant such as leaves or the bark (Timema
californica) and these tend to lack the capitulam or have it greatly
reduced.
The eggs take
anywhere from 3 months to over 18 months to hatch into miniature versions of
the adult, accept that they have no wings. They are generally active and run
around a lot, they climb to the top of, or to the end of a limb of the nearset
vegetation. Most Stick-Insects have 5 larval instars in the male and 6 in the
female, and take from about 3 months to over 12 months to reach maturity. The
females are generally far larger than the males except in those species where
the males actively compete for females as in Eurycantha calcarata where
the males are nearly as big as the females, and Oncotophasma martini
where they are slightly bigger. This is because the females produce the eggs
which are relatively large and she needs a larger abdomen to make them in and
a larger mouth to eat more food and a thus the rest of her body has to be
larger too. The males in many species fly and have longer antennae to help
them find the females. In a number of species of Stick-Insects the males guard
the females after and some times before mating with them This is particularly
evident in species such as, the American Walking Stick Anisomorpha
bupestroides, Anisomorpha monstrosa and The Small Spiney
Stick-Insect Aretaon Asperrimus, males of which will, in captivity at
least, guard anything that looks remotely like a female of their species, such
as a juvenile female of a different and larger species with which they can not
possibly have mated. The life span of many species is about 1 year, however in
many of the larger and slower growing species this may rise to more than two
years after hatching.
Though most
Stick-Insects rely on passive camouflage in order to avoid predators some of
the larger species such as Eurycantha horrida have large spines on
their hind legs which can serve as aggressive tools of self defence against
predators, as well as in competition with other males. While the American
Walking Stick Anisomorpha bupestroides and to a lesser extent Pink
Wings Sipyloidea sipylus have a defensive chemical spray emitted from a
special metathoracic gland, which in the case of American Walking Stick
Anisomorpha bupestroides can cause temporary blindness and considerable
pain to an adult.
