|
The desert locust (''Schistocerca gregaria'') is a species of locust. Plagues of desert locusts have threatened agricultural production in Africa, the Middle East, and Asia for centuries. The livelihood of at least one-tenth of the world’s human population can be affected by this voracious insect. The desert locust is potentially the most dangerous of the locust pests because of the ability of swarms to fly rapidly across great distances. It has two to five generations per year. The last major desert locust upsurge in 2004–05 caused significant crop losses in West Africa and had a negative impact on food security in the region. While the desert locust alone is not responsible for famines, it can be an important contributing factor. ==Life cycle== The life cycle of the desert locust consists of three stages, the egg, the larva known as a hopper and the winged adult. Copulation takes place when a mature male hops onto the back of a mature female and grips her body with his legs. Sperm is transferred from the tip of his abdomen to the tip of hers, where it is stored. The process takes several hours and one insemination is sufficient for a number of batches of eggs. The female then seeks suitable soft soil in which to lay her eggs. It needs to be the right temperature and degree of dampness and be in close proximity to other egg-laying females. She probes the soil with her abdomen and digs a hole into which an eggpod containing up to a hundred eggs is deposited. The eggpod is long and the lower end is about below the surface of the ground. The eggs are surrounded by foam and this hardens into a membrane and plugs the hole above the egg pod. The eggs absorb moisture from the surrounding soil. The incubation period before the eggs hatch may be two weeks or much longer, depending on the temperature.〔 The newly hatched nymph is known as a hopper. It soon begins to feed and is attracted to other hoppers and they group together. As it grows it needs to moult; its hard cuticle splits and its body expands while the new skin is soft. The stages between moulting are called instars and the desert locust nymph undergoes five moults before becoming a winged adult. Hoppers are gregarious and form bands which feed, bask and move as cohesive units.〔 After the fifth moult the insect is said to have fledged but it is not yet mature. It is at first soft and pink with drooping wings, but over the course of a few days, the cuticle hardens and haemolymph is pumped into the wings which stiffen them. Maturation can occur in two to four weeks when the food supply and weather conditions are suitable, but may take as long as six months when they are less ideal. Males start maturing first and give off an odour which stimulates maturation in the females. On maturing the insects turn yellow and the abdomens of the females start swelling with developing eggs.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「desert locust」の詳細全文を読む スポンサード リンク
|