The book has 29 families of flies. (He includes mosquitoes and midges.
"The most distinguishing characteristic for these insects is a pair of well-developed forewings and hindwings (halteres) reduced to stubs.")Most of us probably can distinguish 'flies' from 'mosquitoes', but now we have 27 more different specific families. And then each family can be broken down - though he doesn't do that for most. You can see, though, how the more you know, the more you realize how much you don't know. And if you're honest with yourself, you'll realize that what you don't know dwarfs what you do know. And this should lead to humility.
Going through the pictures, I decided the deer fly seemed the most likely. Especially this:
"These . . . flies have gold and green metallic eyes . . ."So I googled deer fly (family Tabanidae).
Bugguide offers a lot more detail. [my comments in brackets below]
"Medium to large flies, females take blood, and some are pests. Typical characteristics:
stoutly built flies with large squamae (scales above the halteres, also called calypters);
[It is stout. I'm not positive about the squamae. If you click the links to halteres it tells you
"calypter noun - a small membranous flap at the base of the hind edge of the wing in some flies; it covers the halteres."but I can't tell from the pictures they provide and this one I took. There is a lump at about where the wing comes in.]
feet with 3 pads (as opposed to 2); [My picture doesn't show the foot pads]
3rd antennal segment elongated, clearly made up of several fused parts; [???]
3rd antennal segment with a prominent tooth at base in some groups [????]
wing veins R4 and R5 fork to form a large 'Y' across the wing tip." [Yes! you can see the Y pattern of the veins on the wing. Look at the tip of the wing on the left.]
So, I'm not certain, but at this point I'm tentatively identifying this as a deer fly until I get more evidence one way or the other.