Corps of Discovery: Expansion 1 – InsectaExpansion

From BoardGameGeek:

The Corps of Discovery ventures further westward only to find the woods teeming with giant insects. Only an airborne insecticide can put an end to the menacing masses that threaten to overrun the Corps. The ingredients needed to concoct such a poison are readily available from the land itself, but all of your precious scientific gear is back on your boat. In order for you to be able to shuttle resources back to the boat, you must first deal with the Ranidae–a monstrous, frog-like creature that lies in wait just beneath the surface of the river, somewhere between the shore and the ship. -description from the publisher