Dimorphism is the presence of two different forms of an organism in a population.
Many species exhibit sexual dimorphism whereby males and females have a different appearance. For example, males of the beetle Oedemera nobilis have swollen femurs whereas the females have slender femurs.
Another example of sexual dimorphism can be seen in Madagascan hissing cockroaches. Adult males have large lumps on their pronotums whereas females have a smooth pronotum.
Madagascan hissing cockroaches (Gromphadorhina portentosa) exhibit sexual dimorphism. The male is on the left and has large bumps on his pronotum, the female is on the right and has a smooth pronotum.
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