The adult posterior midguts of bftΔ263a/bft24 transheterozygotes display a significant increase in the number of mitotic cells at 14 days post eclosion, as compared to controls.
45% of the expected number of homozygotes survive. Mutant adults lack 50-90% of the interommatidial bristles and in most cases, severely defective structures are seen where the interommatidial bristles normally form. The sockets may be abnormal. Third instar mutant larvae often have abnormal trichoid sensilla in which the shaft is missing.