For much of my walk. I was tormented by a particularly persistent and malignant horsefly which seemed bent on following me wherever I went, despite my feeble attempts to out-run it, my random irritated flailing and the rich selection of curses that I rained upon it and all its ilk .
It has been suggested that the more clothes you have on, the more savage the bugs. If this is true, I dread to think what this one would have been like if I had encountered it while wearing a coat. Possibly I would have had to fight it off with a spear.
Anyway, in between the flailing, thwacking, etc, I considered this problem and came up with MANY THEORIES:
1) Insects identify their victims using infra red (Go with me on this, I read it on a website. Or possibly it was on the radio. Are you saying the BBC lies? It was probably on Radio 4. RADIO 4). Possibly, when you have bare legs and arms, your body is closer to the ambient temperature of the surroundings, whereas if it's cold enough for tights and coats, legs stand out in brillant crimson against the surrounding chill
2) You are more likely to feel the minute tickle of the landing fly on bare skin, and brush it away without realising, before it has time to bite deep. Clothing obfusticates your natural senses and defenses, giving the fly the advantage of stealth. If this one is correct the best costume for dog-walking would be nudity, but I am loath to try the practical experiment.
3) Perhaps flies have an attraction to darker colours? In evidence of this I cite Rosie Roo, whose bare pink chest and tummy should surely be a magnet for pests but never seems to get bitten, and Brythen, who is covered in dark patches and has to gallumph about at a steady 20mph minimum to avoid the attentions of flies.
4) Flies, which evolved primarily to feast on hairy things such as horses, cows, etc, find bare flesh weird and creepy and avoid it. Like sharks, which apparently never eat people, or not on purpose anyway (see note above about I probably read this on a website).
5) Flies are traditionalists. Over thousands of years, they have learned that bare skin signals the presence of a horny-handed son of toil, whereas delicately covered flesh conceals the more delicately tended flesh of the aristocrat. Even in fly terms, evolution is a slow process, so they have not yet caught up with the changes resulting from the sudden proliferation of cheap nylon, lycra, etc.