P. occidentis feeds mainly in dead branches of Parkinsonia florida, the blue palo verde, while Marginitermes hubbardi, another species of drywood termite present in the Sonoran Desert, mainly feeds on the skeletal remains of saguaro. Dry timber being a very difficult food from which to extract nourishment, the termites accumulate an array of about forty symbiotic microorganisms in their gut to help them digest it. All colonies of P. occidentis have this wide range of gut symbionts, suggesting that the diversity is necessary for colony survival.
