If you want proof for how the emerald ash borer can leap across the landscape, check out the latest map from the Pennsylvania Department of Conservation and Natural Resources.

The small insect, an Asian invasive that was first detected in Michigan in 2002, kills ash trees. As it moved through Detroit, the streets became lined with dead or dying trees, and municipalities were strapped for funds as they realized they had to cut the trees down to avoid a public safety problem.

The insect spread quickly, and in 2002 it was first detected in Pennsylvania's Butler County -- not far from the turnpike. Because the insect seems to follow highways, often being found at or near rest stops, officials theorize the transport of firewood is a major route of expansion.

And then earlier this year, when it was found in Bucks County -- no where near any other spotting -- officials figured the only way it could have gotten there was by firewood transport.

They found the dreaded insect in one place -- at a Warrington apartment complex -- but they figure it won't be long before it spreads, or evidence it has already spread becomes apparent.

Meanwhile, look at the map: You can see how the insect spread from west to east, and then made that huge leap to Bucks. It's now in 28 Pennsylvania counties.

Other places it has recently spread to (note the highway and campground spots, indicating probable firewood transport):

• Along I-76 close to Willow Hill, Franklin County;

• Near Brookville, Jefferson County;

• At a campground near Liverpool, Perry County;

• Near the state hospital in Selinsgrove in Snyder County;

• At a campground close to Emlenton, Venango County.

As part of a national survey, crews from the Pennsylvania Department of Agriculture began hanging more than 750 triangular purple traps from ash trees in eastern Pennsylvania in May. The idea isn't to trap the insects to control them, but to detect them. The hope is that you put out the traps and catch nothing.  Crews will continue to monitor the traps and sites through August, officials said.