whats the difference between horse flys and regular flys? do horse fly have big larvae?

Answer 1

Well they aren't in the same family to begin with. Horse flies being in the Tabanidae family and house flies usually being Muscidae. They have very different biologies, as stated before adult female horseflies are blood feeders, the males on the other hand feed on nectar and pollen. Their larvae are aquatic predators which actually have poison glands to help them subdue prey. Another characteristic is that many species eyes many with very attractive colour patterns (not all) .http://bugguide.net/node/view/30613 .
House flies tend to have smaller eyes, the larvae are usually in decaying organic matter (dung, flesh, etc) others are plant pests and eat all sorts of vegetable matter, only a hand few are blood feeders, the best known would be the stable fly which looks like a regular house fly except it bites (usually goes for the ankles...)

There are a number of characteristics that are useful to Id both but are hard to look at without a microscope.
Take a look at these 2 pages should give you an idea of the general differences.
House flies http://bugguide.net/node/view/7266/bgimage?from=24
Horse flies http://bugguide.net/node/view/117/bgimage

Answer 2

Horseflies are huge and will bite the crap out of you. And unlike mosquitoes or fleas or anything else like that, they don't have the common decency to have a small enough mouth that the bites don't bleed.... and it itches like mad... and welts up horribly..... GAH!! I HATE HORSEFLIES!!!!!

Answer 3

The size, horseflies are huge.