Phasmids spend most of their time hidden among their food plants, remaining absolutely motionless. They become active at night to feed and locate mates. Stick insects are sometimes found perching on walls and window screens with their fore legs extended forward. Since most species are colored in various shades of greens and browns, camouflage and remaining still are their first lines of defense. Some species are able to change their colors to better match their backgrounds. Many pretend to be dead when threatened and fall to the ground, where they become lost among the leaves, grasses, and other vegetation. They might even voluntarily break off a leg to distract a predator (PREH-duh-ter) or animal that hunts other animals for food. Several species have bright, contrasting colors to warn predators that they will spray a foul-smelling, milky defensive fluid from glands in the thorax or midsection. This fluid can cause temporary blindness if it gets in the eyes. Winged species will suddenly open their colorful wings and begin to rattle them in an attempt to startle a potential predator.
Males transfer the sperm packet directly into the reproductive organs of the females during mating. After mating the male will remain clinging to the female for several hours or days. In fact, male timemas spend most of their adult lives riding around on the back of adult females. This behavior prevents other males from mating with her. If males are not available, some species of phasmids can reproduce by parthenogenesis (PAR-thuh-no-JEH-nuh-sihs). Parthenogenesis does not require sperm from a male to produce healthy eggs. All parthenogenetic eggs hatch into females. In a few species, males are completely unknown, and reproduction is entirely by parthenogenesis.
Females lay between one hundred and two thousand eggs. Some species drop or flick their eggs to the ground, while others glue them singly or in batches to leaves and branches. A few actually place them inside leaf tissues. Phasmid eggs are very distinctive in shape, size, and color. Seedlike eggs often have a caplike handle that makes it easy for ants to carry them back to their nests. This actually benefits the eggs by keeping them out of reach of other predators. The ants eat only the cap, leaving the rest of the egg intact.
Depending on the species, the eggs will hatch anywhere from about a month to more than a year. The larvae (LAR-vee), or young of the animal that must change form before they become adults, strongly resemble the adults but lack wings (if present) and are not able to reproduce. Phasmid larvae usually molt, or shed their exoskeleton or hard outer covering, six to seven times and can replace lost or damaged limbs as they grow. Adults may live for several months, although some species may live up to three years.
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