Insect dormancy and diapause (two conditions of arrested growth and development)

There are actually two situations when insects stop growing and developing: one is dormancy, which is often directly caused by adverse environmental conditions. As the temperature drops, a series of physiological changes will occur in the insects, such as the accumulation of stored substances such as fat and sugar in the body, the reduction of water content, slow breathing, changes in behavior, etc. If the adverse conditions are removed, growth and development can be restored. For example, in autumn and winter in temperate or cold temperate areas, the temperature drops and food becomes scarce, so some insects enter a dormant state. Some insects hibernate in specific insect states, while others can hibernate in any insect state. If these insects are raised under conditions of suitable temperature and humidity and given sufficient food, they can reproduce all year round.

Another situation is diapause. Diapause is often not directly caused by adverse environmental conditions, but the insect itself has a certain degree of genetic stability. When an insect enters diapause, it cannot resume growth immediately even if it is given optimal conditions. development. Diapause generally has a fixed insect state. According to research, changes in photoperiod are the main factors that cause diapause. Generally, insects that diapause in winter use short days as information to cause diapause. Usually, if the photoperiod is longer than 12-16 hours, they can continue to develop without diapause. , such insects belong to the short-day diapause type. Some insects that enter diapause in summer use long daylight as diapause information. Generally, if the photoperiod is less than 12 hours, they can continue to develop without entering diapause. Such insects belong to the long-day diapause type.

In addition, there are some insects that belong to the intermediate type, which can cause diapause when the photoperiod is too short or too long, and will not diapause only within a very narrow photoperiod range. The insect state in which insects feel the photoperiod is often the previous state of the diapausing insect state. For example, the corn borer diapauses as mature larvae, and its critical light state is the third and fourth instar larvae. How to relieve diapause? It is very simple. When the insect undergoes diapause metabolism for a period of time, it can automatically relieve diapause.

In fact, photoperiod, temperature and humidity are external factors of diapause; hormones are internal factors that cause and resolve diapause. The nutrients and water content in food also affect diapause of insects. For the same insect, if the nutrition is good, there will be very few diapause individuals, but if the nutrition is poor, most diapause will occur. At the same time, the same kind of food has different water content, which also affects the change of diapause phenomenon.

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