Literal translation
he makes a horsefly out of a fly
Meaning
he makes a mountain out of a molehill
Explanation
This expression describes a wildly disproportionate exaggeration, the tendency to inflate a minor fact into a considerable affair. The literal image plays on the kinship and the difference between two insects of the same order: the fly, small, almost harmless, merely annoying, and the horsefly, bigger, whose bite is genuinely painful and leaves a mark. Turning one into the other means subjecting a trivial incident to an inflation of seriousness with no basis in reality, while keeping the two creatures within the same family: a small nuisance simply gets inflated into a bigger one, within that same register. The phrase closely mirrors its French counterpart involving an elephant, but stays within a coherent entomological register, more rural and more modest on the scale of exaggeration. The register is familiar, used to gently mock someone who dramatises, or to laugh at oneself after the fact.