Who's got the biggest testicles? Put your hands down, guys. Bragging rights belong to the bush cricket Platycleis affinis, according to a paper published online today in Biology Letters. The insect's testes (inset) average 70 mg a piece, together making up almost 14% of its body mass. (Human testes, by contrast, make up a mere 0.04% to 0.08% of body mass.) That gives the crickets the largest relative testicles of any known animal. The gift seems to help them score mates, but they don't release any more sperm than less endowed insects. That may be because species with big testicles often have notoriously promiscuous females as well, so the males don't want to spend all of their seed in one place.
See more ScienceShots.