Abd-BCst/Abd-BStP16 show an extreme transformation of A6-A7 to A5, including a large abdominal segment 7. In females this transformation can only be observed in A7, which is larger than normal, having a sternite which exhibits the A3-A6 bristle pattern.
Group 1 allele according to classification of Sanchez-Herrero and Crosby (FBrf0047933).