... that mates while flying around; thus the love-bug nickname. They swarm for mating a couple of times per year across the South, in the spring and fall.
They are totally harmless to humans, and even kind of cute in a tickly way, but the chemicals that come from their little splattered bodies do unpleasant things to automobile paint. As they are also attracted to automobile exhaust fumes, they spend a lot of time hovering low over highways. Anyone planning to drive cross-country in the South during love-bug mating season should take protective measures, such as coating your vehicle with unbuffed paste-wax, applied rather thickly (this forms a barrier between the bugs and the paint), or putting a 'bra' on the vehicle to shield the front end (which still requires frequent washing.)
Oh, one other note: the exhaust-fume thing also explains why they are more numerous at WDW bus-stops; if you wait on the grass a little distance away from the shelter, you won't have as many lighting on you.