---

Tony is right.
Moreover, I think you used a flash, which enhanched the effect.

The larger facets are not only larger, but their lenses have a longer focal distance as well. In plain English, they work as small telescopes.
The male horsefly sees the world enlarged, though grainy (because there are fewer facets there are fewer 'pixels' projected).
Males with large enhanched facets, as far as I know of, are 'sitters':
they sit and wait all day on a leave on the lookout.
Species with more active males (like hovering) tends to have smaller facets.

Theo Zeegers