In which kolbolds have much to say but little to do

Opening description 
At the far end of the roughly dug tunnel stands a few kolblds, lounging by a door. They look startled by your sudden appearance. Two of them have crossbows which they begin loading with palpable nervousness. A third grabs his spear and turns into the door, calls out in kolbolden,"Intruders! Everyone arm yourselves!". The fourth resolutely grabs his spear and stands with a locked jaw.

The setup
The kobolds have dug a large pit trap in the tunnel. It has a search dc of 15, covers the entire width of the cavern and is about 15 feet long. It is 10 feet deep. Burrowed into a side of the pit is a Giant Bombardier Beetle. It is raised from a grub by the kolbolds and trained to attack anything in the pit. After the party uncovers the pit trap or falls into it, the remaining kolbolds turn tail and lock the door behind them.

Aftermath and Loot

the kolbolds have not left much in their entrance. Their are a few coins scattered in the pit, but everything else of value has been hoarded away. The door to their rooms as been locked and barred. It requires a dc 20 open lock check and a dc 13 strength check to open it.