Well if you guessed Drywood termites pellets, you guessed right? Those little brownish colored things at the bottom of the picture are the fecal remains of wood eaten by Drywood termites. Subterranean termites mix their fecal material with the mud/soil and construct mud tunnels or tubes while Drywood termite fecal pellets are kicked out of their colony. These little pellets have little ridges and are fairly easy to identify. Drywood termites which are located within structures are often tented and just a side-note not usually a very big deal in Arizona but we do have them here. The more water we bring in, such as flood or drip irrigation helps to increase the humidity level and allow these termites to gain a strong-hold here. Even after a fumigation takes place, those pellets will continue to fall out – so the only real way to know that you still have them is by an actual swarm. Just one more thing to keep you from sleeping!
By the way this is generally not a “Do It Yourself” project, unless you are able to remove all the wood. In the case above it was a small shed, which I would just remove and rebuild. Which by the way falls into my model of IPM.