The ants get in through a gap between the Ethernet port block and the opening it sits in. Attached is a pic of 3 brand new F200's . On the first radio you could drive a truck through the gap, on the the second radio there is no gap, I can't even get a small flat zip tie into it, on the third radio it's not as bad as the first but even a large zip tie easily goes into the gap. So radios 1 and 3 are ant friendly.
Note that as far as I can tell the Ethernet port opening and the Ethernet port on all the other epmp radios (I don't have any 190's handy to look at) do not have this problem. On those radios the fit between the Ethernet port and the opening is very tight only the F200 seems to have this problem.
So I guess now we add "silicone gap around eathernet port" to the set up process of F200's right after "check F200 for chain imbalance"