General: Creosote Gall Midges (Asphondylia auripila) are one of about 15 species of gall-forming midges that use creosote bush as a host plant. The 15 species divide up the habitat (stems, leaves, flowers) and the timing (rainy periods during spring, summer, fall, and winter). This and four other species use the stems, and these photos were taken during fall.

The various species of midges all look similar, but each species produces a uniquely shaped gall. Asphondylia auripila produces stem galls that form a green ball when the midges are developing, but they turn brown after the midges emerge. These galls do not seem to harm the plant.

Adult female midges oviposits (inserts eggs) into the part of the plant her species prefers, then adds a fungal spore. The fungus induces the plant to produce the gall, and the fungus grows inside the gall, lining the inside of the egg chamber. The eggs eventually hatch, and the larva feeds on the fungus. Looking at these photos, however, it looks as though the larvae might also eat the tips of gall "leaves."

Adults emerge during periods of plant growth associated with winter, spring, or summer rain fall. Interestingly, the evolution of new species in the A. auripila group seems to result from colonizing new parts of the same plant and colonizing different seasons. Learn more about this species on Wikipedia.