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| Life cycle of a cockroach |
By:
Snigdha |
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when sexually mature, the male and female ccckroaches pair, generally during night, from March to September. The process of copulation lasts an hour or more, during which the tip of the abdomen of the male is inserted into the genital pouch of the female and their hook-like gonapophyses get interlocked. The spermatozoa, enclosed in a spermatophore, are laid into the genital pouch and passed into the spermatheca. to be stored until the time for egg laying.
The ova are generated in the upper parts of’ the ovarian tubules. During their descent, yolk is deposited in them so that the ova increase very much in size. Sixteen ova, one from each ovarible, usually descend together into the genital pouch, where they are fertilized by the sperms ejected from the spermatheca. Each egg is enclosed in an oval shell with several minute pores, called micropyles, through one of which a sperm enters to fertilize the egg.
Ten days or about a fortnight after copulation oviposition starts. In the genital pouch the fertilized eggs are surrounded by the secretion of the colleterial
glands, which hardens into a handbag or purse-shaped egg-case or ootheca. Sixteen eggs are packed together in an ootheca in two rows, very much like cigarettes in a cigarette-case. The female cockroach carries the egg-case protruding from the tip of the abdomen for several days till it is deposited in a warm, sheltered and dark place. The mother takes no care of the eggs or progeny. The eggs are rich in yolk, which provides enough food to enable the young to develop sufficiently to be able to feed.
The freshly-hatched cockroach is called a nymph. It is a delicate, semi-transparent and almost colourless creature with black eyes. The nymph bears nearly all the adult characters but differs in size, in being sexually immature, and in lacking wings. As the nymph grows, its exoskeleton, being non-living and therefore unable to grow, becomes too small and at intervals it is cast off by a rupture on the back. This process of shedding of the exoskeleton is termed ecdysis or moulting. The nymph undergoes six or seven moults in about thirteen Months to grow to the adult stage. Wings and all the adult characters appear fully developed at the last moult which also marks the end of the growth.
The life history of the cockroach is much simpler to that of many insects, such as butterfly, housefly, mosquito etc., in which the young hatches in a form very unlikely
Adult and, in order to become the adult, it passes through changes of form and habit that are collectively known metamorphosis. The development of cockroach is directly showing little or incomplete metamorphosis or hemimetab as contrasted to indirect development of butterfly, show complete metamorphosis or holometaboly. |
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