Formosan subterranean termites are on the USDA’s National Invasive Species list due to their ability to cause structural damage to buildings and their competition with native termite species. In a throw down between native subterranean termites and Formosan subterranean termites, the Formosan termites outpace and outcompete native subterranean termites. While native subs cause structural damage over time, we have very effective means of controlling them. Formosan subterranean termites cause HUGE amounts of damage in very little time and control requires a multi-pronged approach over a long period of time.


Signs of Formosan subterranean termites include mud shelter tubes on slabs, foundations, or piers; tiny holes appearing in walls, ceilings, or hardwood floors; painted wood that appears bubbled; bulging walls; sagging floor; a chewing sound coming from the walls (yes, some people can detect this sound); and winged reproductive termites.


Formosan subterranean termite reproductives, or alates, look like a plump grain of brown rice with four long, narrow wings. The wings are at least two times the length of the body of the insect. The body does not have a narrow, or pinched, waist. The reproductives of all termite species in San Diego appear similar. It takes a trained professional to provide a definite identification. 

Winged Formosan subterranean termite side view La Mesa

Winged Formosan subterranean termite side view La Mesa 2018

Reproductive Formosan subterranean termite La Mesa

Reproductive Formosan subterranean termite La Mesa 2018


The behavior of Formosan subterranean termites is distinctive. Unlike native subterranean termites, Formosan subterranean termites are extremely active, don’t flee when disturbed, and the soldiers are particularly aggressive. Formosan subterranean termite soldiers will bite your finger if you get close enough, but they cannot break the skin and are harmless to humans and pets.

Formosan subterranean termites La Mesa Biting a finger

Formosan subterranean termites La Mesa Biting a finger 2018

Formosan termite damage follows the grain in structural lumber. Unlike native termites, Formosan termites feed on both the summer and spring wood leaving large hollow spaces. These hollows spaces are called galleries. Unlike native termites, Formosan termites clean out debris from their galleries leaving them practically soil free and covered in whitish spots.

In severe infestations, Formosan termites form nest-like structures in hollow spaces and wall voids with a combination of termite excrement, macerated wood, saliva and soil. These “carton” nests are constructed near a feeding site. A single Formosan termite colony may have several of these auxiliary nests containing secondary reproductives. One sign of these hidden nests is a bulging wall.

In addition to eating structural lumber, Formosan termites have been known to attack in over 50 species of living plants including citrus, pepper trees, wild cherry, cherry laurel, ash, sweet gum, cedar, willow, wax myrtle, Chinese elm, live oak, and white oak. Because Formosan termites survive in the yard as well as the house it is important to inspect and treat the area surrounding an infested house.

Formosan termites are aggressive eaters and have been known to chew through non-wood materials in their search for wood. They have attacked plastic, asphalt, plaster, rubber, and thin sheets of lead and copper metal. The creosote on utility poles does not deter Formosan termites and are at great risk of damage.