Clasping Twig Gall Wasp

The life cycle of Disholcaspis prehensa alternates between an asexual (agamic) generation and a sexual generation, producing two different types of galls at different seasons of the year. In the spring, females from the previous sexual generation oviposit in young twig tissue, forming conspicuous mushroom-shaped galls which mature by early summer. The base of each gall has sharp edges and broadly wraps around the twig it rests on, giving rise to the common name, clasping twig gall wasp. The galls are 7–10 mm high and around 10 mm wide at the base. They tend to be more red in color on the sun-facing side, and more yellow on the shaded side, eventually browning with age. The larvae are housed in an elliptical chamber at the base of the gall, and they emerge from the sides as adults in late winter or early spring. The adults that emerge are all female, and they reproduce parthenogenetically, laying their eggs into the dormant leaf buds of the California scrub oak. The new galls develop the next spring as the oak's leaves begin to open. Unlike the galls of the asexual generation, these spring galls remain hidden within the bud. They are only 2.2–3.5 mm and oblong, with a light brown color. By late spring, the new sexual generation emerges from holes near the apices of their respective galls. At this stage, the adult males and females will mate to begin the cycle again.