In Vayikra (11:23) it says:
But all winged swarming things, which have four feet, are a detestable thing unto you.
On which Rashi (quoting the Sifra aka Toras Cohanim) says: Go and learn if there was 5 legsit is pure.
How about 6 legsNowadays, most flying insects have 6 legs, so are they also kosher (i.e. they have more than 4 legs)?