What are those orange balls found on some telephone wires? What purpose do they serve?
Near an airport, perhaps?
oops, hit reply too soon.
Usually the orange balls are near airports, or private airstrips in order to make them more visible.
The wires, that is.
an they’re not telephone but power lines
I’ve seen Orange Balls on telephone lines that are WAY out in the country, no where near an airport.
They are at the entrance to a state forest park (Tar Hollow State Forest, in Ohio).
I can only guess it’s in case a helicopter needs to land, or if they’re driving some big truck thru the park.
Cecil has covered this:
I hear a lot of people say this, but speaking as someone who sees these things from the air rather than the ground, I have to say that almost always these things are near an airstrip of some sort.
The misunderstanding comes in with the question “what is an airport”? I’ve seen landing strips as short as 800 feet (or even less, if used by ultralights), turf-surfaced which, if located on the other side of a treeline from an ground observer are more or less invisible.
Helicopter landing areas are even smaller, but still have the “orange balls” in the vicinity. A national park that occassionally has to helicoptor clumsy tourists to medical care might have a designated landing area(s) decorated with “orange balls”.
A place that is genuinely not a landing area that you’ll see them is around field that get crop-dusted, where you have agricultural pilots flying at extremely low altitudes.
Another circumstance might be over pipelines that are checked from the air - this also requires low altitude flying and if specified routes are followed then “orange balls” can make low obstacles much more visible and thus the whole operation safer.
Who is this Cecil character, and why is he cribbing my answers? 
I saw an airfield in the middle of nowhere in the Lousiana swampland this past summer. On reflection, I concluded that it was to provide landing strips for the mosquitos. 
Since I moved to my present location, I have passed a set of orange balls about once a week. Every time I did, I thought it was funny becuase there was no airport nearby. Then one day a few months ago I saw an airplane parked by the house on the other side of the road. All this time I thought it was just a really big front lawn when it was really a landing strip.