1961 August 17, New Scientist, volume 11, number 248, Reed Business Information, ISSN0262-4079, page 413:
In his Mantissa Plantarum (1767) and Mantissa Plantarum altera (1771), [Linnaeus] regularly used ♂, ♀ and ☿ for male, female and hermaphrodite flowers respectively.
1990, Charles S. Churcher, “Cranial Appendages of Giraffoidea”, George A. Bubenik, Anthony B. Bubenik, Horns, Pronghorns, and Antlers: Evolution, Morphology, Physiology, and Social Significance, New York: Springer-Verlag, ISBN 9781461389682, chapter 1.5, page 183:
Figure 2. Ossicones, secondary ossification, and sinuses of Giraffa: A Lateral aspect of skull showing courses of veins, areas of dense ossification (heavily stippled) and lesser secondary ossification (lightly stippled), and outlines of skull roofs of male (♂) and female (♀) adults. (After Spinage 1968b.)
2015 July 6, Andy Burns, “Re: C4 last leg”, in uk.tech.broadcast, Usenet:
I was quite surprised that a few of my friends found the male ♂ (mars) and female ♀ (venus) symbols on toilets in pubs/bars confusing ...