Question

How does temperature have an effect on the growth of insect eggs and larvae?

Answer 1

Insects are cold-blooded animals and cannot generate their own body heat like warm blooded animals, so has to depend on the surrounding environment to get warmth. Thus temperature is a crucial aspect in the growth and development of insect eggs or larvae. An optimum temperature is a prerequisite for complete development at a certain stage of the life cycle of insects. The growth rate of the insect eggs or larvae is controlled by three factors:namely, (i) the growth rate of the last instar larvae that determines the body size, which is strongly dependent on temperature. (ii) a temperature independent relation between the mass at which juvenile hormone secretion stops. (iii) With increasing temperature, there is a decrease in the interval to cessation of growth after attaining the critical weight.

Generally there is a linear relationship between growth rate and temperature with an optimum temperature at which the growth of eggs or larvae develops at a fastest rate. This temperature is called threshold temperature and can vary at each stage of the life cycle of an insect. Below and above this temperature threshold, the growth will come to a halt, but will not be killed until a lethal temperature is attained. Normally, the minimum and maximum temperature threshold for an insect is 10⁰C and 35⁰C respectively. The growth in body size may also be attributed to the fact to the cell size and cell number. The ecdysone hormone regulates the cell size and thus terminates the growth phase of development which is temperature dependent.