189 BC, somewhere in present day Greece
The Roman Fulvius Nobilior stands outside the Aetolian colony Ambracia and commands his army to lay siege to the city. But each time the Roman battering rams fell a section of the wall, they are met by a repulsive force of Aetolians erecting a counter wall. After days of struggle, Fulvius opts for a more creative path and orders his men to begin digging. When the Aetolians notice the heaps of soil outside their wall, they commence digging themselves, making a deep trench along the interior of the wall. From the trench they listen. Using brass plates, they detect the faint sound of mining, along and underneath their wall. Where they hear it, they dig tunnels perpendicular to their trench, under the wall.
At first they meet the Romans with a clash of spears and shields, but the tunnels are such close quarters that neither side can do much damage. After some time, a few Aetolians approach the front lines carrying an earthenware jar riddled with holes and full of feathers. The feathers are aflame, and the men cover the space around the jar, so that only two holes are left through which they can shove spears toward their enemies. The Romans look on as the Aetolians stand behind the flaming jar and compress a blacksmith’s bellows. Flames and smoke come gusting towards Fulvius’s men, the noxious fumes driving them back into the open air outside the city’s wall once again. The siege will last another day at least.
2012, somewhere in present day New Jersey
A Southern Pine Beetle begins its siege on a pine tree by chewing and burrowing through a crevice in the bark and into the phloem of the tree. But the tree, like the city of Ambracia, sends forth its defense through the entry tunnel, exuding viscous and toxic oleoresin in hopes of repelling the attacking beetles. Many beetles are caught in the flow and entombed in crystallized resin, or pitch.
But the SPB, unlike the Romans, is ready for the toxic defense. Adult beetles can survive long periods swimming in resin, and they have developed a behavior called “working the pitch tube,” to combat the flow of resin. The beetle uses its legs and elytra (hardened forewings) to move resin from the phloem to the entrance. She (females begin gallery construction) is creating a pitch tube of resin at the entrance, a globule of pitch with a central passageway for entry into the tree.
But the war has many fronts
The pine tree may be able to survive a single beetle attack, and the Aetolians may be able to withstand the siege if they could concentrate their army in Ambracia. Unfortunately, the Aetolians are also under attack at their coast by the Illyrians and Achaeans, and at the city of Amphilochia, by the Macedonians. And the pine tree is subjected to a mass attack as well; the first beetle to chew into the tree releases pheromones that signal others to join the advance. If the local population is high enough, the tree is soon covered in pitch tubes. Strapped for resources and facing attack from all sides, the Aetolians negotiate with the Romans and give up control of the city, and the pine tree drops its now-reddened needles and dies.