Homozygotes and hemizygotes survive at all temperatures from 18oC to 29oC; complements the lethality of lethal alleles. The suppression of f is temperature-sensitive, but the sensitivity is of opposite sign from that of other temperature-sensitive alleles; f su(f)23 flies raised at 18oC have suppressed forked bristles, whereas those raised at 29oC are forked; the temperature-sensitive period sharply confined to the short interval at which bristle development is initiated. Does not appear to enhance RpS17.