Do you catch more flies with sugar than you do with, ah, fecal matter?
Dear Straight Dope:
One of the more annoying folks with whom I work has taken to proclaiming, "It's like I've always said, you catch more flies with sugar than you do with shit" in a Gomer Pylesque falsetto. Having grown up on a cattle farm and observed flies' affinity for feces (interestingly, they seem to prefer bullshit over cowshit--go figure), I doubt this very seriously. Are you aware of any empirical evidence to support either side of this debate?
Your instincts are correct. Of the 100,000 species of flies, far more would head for a cowflop than a sugarcube, so in terms of diversity of flies attracted, the feces wins. The same would hold for absolute numbers; droppings are a rather ephemeral resource, and competition for them is fierce, so natural selection favors flies (and beetles, etc.) that can find the stuff quickly before it loses its . . . um . . .desirable qualities. Flies gather fast and thick on a prime piece of poo.
That being said, this clearcut difference would diminish if your colleague used a more familiar variant of the phrase, and specified "honey" or "syrup" as the alternative attractant. Those would give off odors of fermentation, unlike refined sugar, and a lot of flies go ga-ga over fermenting sweets. The results of that particular side-by-side contest would be less predictable, and under certain conditions (like holding the test in an orchard), the honey/syrup might be expected to attract more flies (most about 3 mm long). Of course, the version I'm most familiar with involves vinegar, and that doesn't draw flies at all.
However you look at it, he needs to adopt a new saying, as you suspected.