Insects From Eggs Without Fertilization

The sex of hymenopteran insects normally is determined by the number of sets of chromosomes. Unfertilized, haploid eggs have only their mother's set and develop as males. Fertilized, diploid eggs have chromosome sets from both their parents and develop as females. Mated females have control over when sperm is released from the spermatheca to fertilize eggs. Therefore, they can adjust their offsprings' sex ratio in response to a variety of cues. Hymenoptera are particularly susceptible to manipulation of sex determination by parasitic microbes. Wolbachia, for example, can alter sex determination so that haploid, and therefore unfertilized, eggs develop as females.

Aphids have complex life cycles that often include female forms that reproduce parthenogenetically, producing female clones of themselves. In such aphids, diploid oocytes form in the germarium and begin development without fertilization.

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