Why would this influence the widths of the city streets?
I could see them doing this if, say, woods or stagnant water were on one side of the street and houses on the other, and they wanted to keep the mosquitos on their side of the street (assuming that this belief in limited flight ability is true). But a city is made up of lots of things all over the place. Was the idea that mosquitos couldn’t fly over 60 feet supposed to mean that the outer ring of streets acted as a cordon sanitaire, with mosquitos dropping dead before they crossed this cobblestone desert?
If so, then you don’t need more than one such wide street ringing the city.
I’ve never heard or read anything like this. Certainly people didn’t think flies were of limited range. I never heard or read one thing or the other about mosquitos, so I can’t definitely rule it out. But as an excuse for wide streets everywhere, I can’t even see the logic.
edited to add: One good wind-gust would blow mosquitos over your cordon sanitaire, thus getting around yopur clever scheme. Just another argument against it being true.
But did they make the connection between mosquitoes and malaria and other diseases back in the 1700s? IIRC, it was though “bad air” (hence the name, malaria) caused diseases, in which case the width of the street would have meant nothing.
A possible reason for wide streets. Narrow streets would tend to be damper and darker. They might rarely dry out properly like a wide open street would. The narrower street would shield more of the wind as well.
As a Deep South denizen, it certainly seems to me that there is some correlation to places being dark, damp, and protected from the wind and having more skeeters.
They definitely did not. But the OP isn’t suggesting they were preventing disease-bearing mosquitos from crossing the street. The implication seems to be that you would simply avoid the numerous bites from the mosquitos – a laudable goal in itself.
New Hampshire Dept. of Health and Human Servicessays mosquitoes can smell humans up to 60 ft. away. Other websites say that is about detecting CO2 from our breath. Doesn’t sound like knowledge available in the 18th century anyway. Probably some creative mixing of factoids and fictionoids.