Wasps Choose the Sex of Their Young—but Climate Can Foil Them

It's a good thing human sex isn't determined the same way a parasitoid wasp's is, because "sugar and spice and everything nice" is much easier to rhyme than "sperm and moderate temperatures." But that's what little wasp girls are made of. A mother wasp can choose the sex of each egg she lays by deciding whether or not to fertilize it. Depending on the temperature of her environment, though, she may not get her way. Whether you are biologically male or female isn't really determined by spices, snips or snails, of course, but by the genes you receive from your parents. Outside of the mammal world, things get more interesting. In reptiles such as turtles or alligators, the sex of a developing egg may depend on the temperature of its nest. In certain insects, every fertilized egg becomes a female, while every unfertilized egg becomes a male (who has half ...