This one is actually about my research on the very, very promiscuous red flour beetles. In this paper we explored different explanations as to why they mate so darn much. Access the article here.
Summary: Males transfer more than just sperm when mating and some of those transferred substances can be beneficial to females. We found that in red flour beetles, an insect that lives in dry grain storage sites and does not drink, females benefit by receiving moisture from mating. Additionally, we found that providing moisture to females reduces male life span. We suggest that these sex-specific effects of mating have influenced the evolution of other reproductive traits in this species.