There are many similarities and differences between drywood termites and subterranean termites. The important difference when it comes to treatment is nesting habits. Subterranean termites nest in the soil and drywood termites nest directly in the wood they are eating. Treatment of subterranean termites vs. drywood termites differs because of this basic difference. In order to control Subterranean termites you must treat the soil at the probably entry points to the structure and eliminate as many conducive conditions as possible. Subterranean termites must move back and forth between the nest and food source using shelter tubes in order to survive. When they pass through treated zones in the soil they become contaminated and die. In order to control drywood termites, you either fumigate the entire structure or perform some type of substandard localized structural treatment.
“Evidence” of termites as described in most termite reports is usually a polite word for termite poop! If you have six sided hard pellets that sometimes look like grains of sand, you probably have drywood termites. If you have dirt-like tunnels (composed of soil, saliva and feces), you probably have subterranean termites. These tunnels serve as protection against the environment and predators, as well as help hold in much needed moisture.
If the wood damage you see appears to be packed with dirt, be limited to the soft wood (not hard rings), and follows the grain of the wood, it’s likely from subterranean termites.
If the wood damage you see has hard fecal pellets, is both with and across the grain of the wood and has smooth gallery walls, it’s likely from drywood termites.
Keep in mind that these are general guidelines and that I have seen both subterranean termites and drywood termites in the same wood, apparently living in harmony. If you suspect that your home has infestations like I have described, please do not wait to call for an inspection by an expert. Termites are not likely to be one of those projects that a “Do-It-Yourself” approach will work.