The length of the central core of the arista is reduced in fry⁰²²⁴⁰/fry⁷ flies and the arista laterals are branched.

Mutant animals show branching of the arista laterals. Most often the branched laterals are derived from an elongating lateral which is normal initially and then splits at or near the distal tip. Both of the resulting arms continue to elongate and the location of the branch-point moves distally. Generally, the extent of branch-point movement is much greater than that of arm elongation, although this varies. The relative extent of elongation of each arm also varies. Branched laterals can also arise from the de novo formation of a new arm well proximal to the distal tip, probably due to fraying of a lateral. Again, both arms typically continue to elongate and the branch-point moves distally. There is also substantial variation in the relative extent of elongation.