On H. microcephalum the gall [attributed to Asphondylia autumnalis in this work] is formed of the enlarged, but scarcely thickened corolla of the disk flower.
The top of the flower is united as in the bud. No injured ray flowers were observed. The color is yellow, darker at the top; only slightly protruding from the surface of the tops of the other disk flowers. The galls are three or four times the width of normal flowers. Only a single flower is changed in each gall and one larva is in each.

Adults emerged December 10 to 19; seven of undetermined sex and twenty-five males and seven females. Although this weed is common, the gall is very local in distribution, and not at all common.

- RH Painter: (1935) The Biology of some Dipterous Gall-makers from Texas^©