Females carrying bcd^{A52-56.T:Ivir\HA1} produce defective embryos which can be divided into two classes according to the severity of the head defects; moderate (the head is recognisable, the mouthparts are formed but incorrectly positioned, sometimes being detached from the rest of the head skeleton, the dorsal bridge and posterior wall of the pharynx are often not formed and the Lateralgraten are reduced or missing) and severe (only a scrambled remnant of the head skeleton and mouth parts is present, or the entire anterior region is missing or the anterior has a hole). For both classes, the anteroposterior polarity is intact, filzkorper are detectable, but often reduced and the denticle belts are often fused or distorted, frequently lacking the entire A4-A7 region.