The Borer Beetle burrows by secreting a highly concentrated acetic acid, which quickly dissolves carbonate rock. The animal absorbs essential minerals and nutrients by drinking the neutralized slurry, which it then uses to secrete a protective exoskeleton of chitino-phosphatic plates. The beetle can go through several instars before reaching sexual maturity, each time shedding its old carapace before undergoing a growth stage and then secreting a new, larger exoskeleton. During the growth stage it is completely vulnerable, and unable to move or protect itself; it therefore ensconces itself in a deep burrow before undergoing ecdysis. Unlike other insects, Borer Beetles continue to molt and grow in their adult stage, and their upper size limit is unknown.
Borer Beetles are predaceous carnivores who ambush cavern-dwelling prey by undermining passage ways with a network of burrows. When the prey passes over the burrow network, the passage collapses and the beetles fall upon the stunned creature, spraying it with acid then dismembering it with powerful pincers.
Borer Beetles are superficially similar to the Fire Beetle, but can be distinguished by bright green mottling on the carapace and an accessory secretory organ on the dorsal surface.
Beetle, Giant Borer (No. Encountered: 1-3)
Armour Class: 4 Special: Acid spray
Hit Dice: 2 Move: 12 (1 when burrowing)
Attack: Bite HDE/XP: 3/60
The Borer Beetle can shoot acid from its accessory organ in a pressurized stream up to fifteen feet away, but can only do so once before needing to recharge its reservoir. This assumes a beetle that has just achieved sexual maturity. Older, larger beetles have much larger acid reservoirs and may be able to fire an acid stream several times. The acid deals 2d6 damage and continues to burn for 1 point of damage each round thereafter for 1d6 rounds. Armour does not protect against the spray; only shields and dexterity bonus can help prevent the target from being sprayed. While the acid will etch metal armour given time, if it is wiped off quickly it will not cause immediate damage.