A 5.6kb PstI-HindIII fragment from the Abd-B gene (50,504 to 44,912, coordinates according to FBrf0083285) which includes the Abd-B m promoter region, the initiation site of the Abd-B m (or A) transcript and the sequence encoding the first 5 amino acids of the Abd-B m protein is fused to lacZ. In addition, a HindIII fragment from the Abd-B 3' regulatory region (64,580 to 59,073) which includes the iab-8 regulatory region and the Fab-8 boundary is fused upstream of the Abd-B promoter sequences.