Oak bullet galls arise from twigs and branches. They are produced under the direction of several species of cynipid wasps (family Cynipidae) in the genus Disholcaspis; thus, there are several types of bullet galls. All are more or less rounded and measure about 1/2" in diameter. Colors vary from light green, to reddish-green, to light brown. Some bullet galls are covered in very fine, short hairs, while others are completely smooth. They cause no appreciable harm to their oak hosts because they do not disrupt vascular flow.
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