Monday, October 18, 2010

Camouflage Masters - Stick Insects

Image :

Look is that a stick walking? No it is not the stick that is walking it is an insect which is called as "Stick Insect" by the scientists. Stick insects are habitually termed as "Walking Sticks". They belong to the Phylum-Arthropoda, Class- Insecta, Order- Phasmatodea. The insects belonging to this order may range from minuscule to giant size. The stick insects resemble with the leaves or twigs and are green or brown in color. They tend to remain motionless for a long time and hang from the plants, shrubs or trees. Their camouflage is a powerful weapon for their protection from their foes. They are herbivorous and feed on leaves only preferably the broader leaves. Females are larger in size as compared to that of males and are incompetent for flight while the males can fly swiftly. Females have only capability for gliding.

There are two families of stick insects: Phylliidae and Phasmatidae, in Australia. Most of the stick insects belong to the family Phasmatidae and only one species is recognized in Phylliidae. Female stick insects are larger in size. The head is gifted with two large compound eyes and antennae measuring 20mm in length. The thorax is 30mm long with some black dots. Fore-wings 15mm long, hind-wings 30mm long that covers two and a half of the abdominal segments. The thoracic legs possess spiny extensions. Abdomen bears ten segments of which the last bears two cerci of 10mm. Females are brown to pale green in coloration with brown tegmina. Males are smaller in size with antenna 35mm and hind-wings 40mm long huge in comparison to that of females. Tegmina 10mm long, thorax 15mm abdomen with ten segments 60mm in length. Fore-legs are deficient of spines while the mid and the hind legs have well organized spines. Cerci same as that of females. Males may be green or brown in coloration.

The mating process of stick insects is fascinating. The mating pairs are seen joined by their anal ends. They restore their mating posture for many hours. After copulation the male stick insect dies two days later. The females lays about 150-200 eggs and then dies within a week after laying eggs. Eggs are 3mm long, dark brown to black in color. The stick insect drops the eggs to the ground during summer and hatch in august to September. Eggs have a tough hard shell bearing capitulum which is pushed by the baby while coming out. the eggs resemble the seeds. The hatched larvae are 13-15mm in length and are very active. They resemble their mothers except wings with very short antenna. They also resemble their mother in sitting position. They undergo various moulting stages before becoming adult. Stick insects are confronted with the phrase-"Camouflage Masters". Their this adaptive strategy is an efficient tool that guards them from their opponents.

Their body shape and dynamic color which resembles the parts of the plants. When they stay motionless they keep their front legs in front of their head making them look like the twigs or branch. they preferably feed at night while during the day time they remain motionless on the plants. They usually consume whole plant leaf without leaving even a single part. They are often blown by the wind. their eggs resemble seeds thus providing an effective means from protection from the enemies. The Goliath Stick Insect drops its scat at such a distance that it remains unnoticed by the Predator. When molested by the foes they sometimes drop to the ground and act as they are dead a phenomenon called "catalepsy". After each moult they eat their shedded skin as it is enriched with nutrients, and can also prevent them fro predators. Every insect is well adapted to its environment that helps it to be well protected from its enemies. Nature provides the insects an protective shield that is responsible for the presence of an insects in many typical habitats. The defensive strategies of insects provides them to be successful taxa.

Navodita Maurice

No comments:

Post a Comment