Bestoutwest":3gtiftg0 said:
Do you have empirical evidence to back this up? How about you get a $1,000,000 grant from the US government to actually settle this.
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.