FlyBase curator comment: this entry is used to capture phenotypic information when the particular allele (or allele combination) used by the author could not be determined but the context of the experiment suggests that the phenotype being described is some kind of loss of function.
Homozygous clones in the wing induced by using Scer\FLP1Scer\UAS.cCa expressed under the control of Scer\GAL4vg.int2.1 result in ectopic veins between L3 and L4 and fusion of veins L3 and L4.
Flies often have a vein segment running between wing veins L3 and L4.