Ecology Of Eggs

Eggs, the first life stage of insects, can be important ecologically. For example, eggs are the diapausing stage in many insects, with embryogenesis stopping at a species-specific point. Eggs of silkworms (Bombyx mori) have an obligatory diapause that coincides with winter under natural conditions. Embryonic diapause has been studied extensively in silkworms because delayed development can be a nuisance from an industrial perspective. Gypsy moth eggs also diapause during winter, but they arrest development at a later stage. Embryos complete embryogenesis and overwinter as unhatched larvae.

Daylength is the most common cue for inducing diapause, but moisture, temperature, and food quality can also be important. The environmental cues that cause eggs to stop developing can be detected by females and then passed on to signal the eggs. Alternatively, the cues can be detected directly by the eggs and embryos. Later, eggs must break diapause in response to another environmental combination of daylength, temperature, and moisture.

Eggs are rich sources of nutrients and therefore pose a great "temptation" to parasitoids, parasites, and predators. Insects protect their eggs in a variety of ways. For example, eggshells can be thick and protective, or cryptic (difficult to detect). Eggs can be laid in protected places. Primarily females, but sometimes males, can contribute chemical repellents or toxins to eggs to deter attacks. A variety of insects stay with their egg masses and actively protect them.

See Also the Following Articles

Diapause • Ovarioles • Parthenogenesis • Spermatheca • Symbionts • Vitellogenesis

Further Reading

Chapman, R. F. (1998). "The Insects: Structure and Function," pp. 298—312.

Cambridge University Press, Cambridge, U.K. Hinton, H. E. (1981). "Biology of Insect Eggs," Vols. 1 and 2. Pergamon Press, Oxford, U.K.

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