Female genital dimorphism in a spider

Amer. Mus. Novitates, 2001;
http://dx.doi.org/10.1206/0003-0082(2001)329<0001:ANGOPS>2.0.CO;2; PDF
Journal of Zoology, London, 2001;
http://dx.doi.org/10.1017/S095283690100139X; PDF
Male Ciboneya antraia. The genus Ciboneya is endemic to Cuba, and this particular species is extremely rare among arthropods by showing female genitalic dimorphism: females come in two distinct morphs (below), and each female is able to produce offspring of both morphs.

Macrogyne (above) and microgyne (below) females of Ciboneya antraia.