This insect ["Bucculatrix fusicola" (misapplied here to B. simulans Braun 1963)] produces the so-called spindle gall on the stems of sunflowers....In the region of Austin, Texas, the gall has been collected only on the sunflower, H. annuus...
Most frequently the galls produced by this lepidopteron are found on the main axis of the plant, but they also occur on the secondary branches. The shape of the gall is apparently greatly dependent upon the size of the stem upon which it is formed. On small stems, galls are usually spindle-shaped and symmetrical, and resemble the original description as given by Braun. However, if the gall develops on a stem more than a centimeter in diameter, it generally appears as a small bump or swelling on only one side of the stem. Galls in this area are from one to two centimeters in length with an average of about one and a half centimeters. They average somewhat shorter than those originally described by Braun which averaged approximately two centimeters in length, and many have a greater diameter. Braun's galls had a maximum width of one-half a centimeter, but in this region, some are as much as one centimeter in diameter. Variations in the size and shape of the galls are indicated in plate III. Galls were first obtained in the field in late July, but they occur only in small numbers until somewhat later than this.

The life history of this species is described and the galls and cocoons figured by Breland and Schmitt under the name Bucculatrix fusicola Braun. The galls are somewhat variable in shape (as figured) often appearing as a swelling on the side of the stem. The larvae become full-fed in the fall passing the winter in the larval state within the gall, leaving the gall to spin and pupate in the spring; a raised ring may encircle the exit hole of the larva.