Scientists have found a bushcricket species with testicles that account for up to 14% of its body weight.
It is the animal with the biggest testicles in relation to its body weight, they write in Biology Letters.
In a study of their mating strategies, the team found they release only small amounts of sperm at each mating.
That suggests the big testes are for mating with many females, not producing competitive volumes of sperm for each encounter.
Significant research across the animal kingdom has shown that male testicle size is correlated to the degree of promiscuity within a given species.