There is such a thing as a free lunch. And a free breakfast. And a free dinner.

And a free snack.

That is, if you're a freeloader fly.

If you've ever watched a spider snare a bee or other insect in its web, and wrap it like a fit-to-be-tied holiday present,  you've probably seen tiny little freeloader flies dining on the prey.

They are so tiny--usually 1 to 3 mm in length--that it takes a keen eye to spot them if they're not moving. The eyes are often red though "this need not be obvious because many species of the flies are small and dusky."

The close-up below is a hand-held photo taken with a Canon EOS 7D with a MPE-65mm lens.

Freeloader flies belong to the family Milichiidae. The close-up below may be in the genus Desmometopa, but it's difficult to tell by the image, says Martin Hauser, senior insect biosystematist
 with the
 Plant Pest Diagnostics, California Department of Food and Agriculture.

As it turned out, the spider dropped its prey and the freeloaders flies didn't have to leave the table.