As far as humans are concerned, sexually-transmitted infections are things to avoid. But imagine if these infections didn't cause death and disease, but gave you superpowers instead. It may sound like a bizarre fantasy, but it's just part of life for aphids.
Aphids mostly reproduce without sex
They only have sex once in autumn,
Why then would a female aphid choose to have sex at all?
They may be trying to receive sexually-transmitted infections from other aphids
Aphids carry various strains of bacteria inside their bodies. These 'symbionts', far from causing disease, actually provide the aphids with useful abilities
allow them to feed off a greater variety of plants
ability to withstand higher temperatures
Aphids are commonly targeted by parasitic wasps
aphids that carry the symbiont Hamiltona defensa avoid this cruel fate
If other insects trade in sexually-transmitted bacteria, we could potentially use these exchanges to our advantage
reduce the spread of sleeping sickness
clipped from: scienceblogs.com 
