Unlike subterranean termites that invade our homes from underground, drywood termites actually enter our home above ground through cracks, unscreened soffits and gable vents. They typically first infest exposed wood such as window and doorframes, trim boards, eaves, attics and crawl spaces. Drywood termites remain hidden in the wood on which they are feeding and are seldom seen. 
At certain times of the year, primarily spring and summer, king and queen drywood termites will emerge from the colony and take flight. The purpose of these flights is to establish new colonies. The swarming typically takes place at night, but can be quite substantial.
Evidence of swarming termites, termite wings and pellets are signs of an infestation.
Termite wings are often present after a swarm and are typically found in small piles near window ledges or other light sources.
Drywood termites excrete pellets of partially digested wood. These pellets are pushed out of areas where termites are feeding and often accumulate in piles on window sills, baseboards and other wooden objects. You may see little holes above where the pellets were found. These holes were created by the termites as they kicked the pellets out.
The best way to protect your home from a termite infestation is having a professional termite protection program and an annual inspection.