P{GawB} excision line.
Many hemisegments show loss of serotonin neuron: a few abdominal segments exhibit the mitotic pair of serotonin cells but a large number have single cells, no serotonin cells are present in the thoracic segments. nub and zfh2 staining reveals the more medial serotonin cell of the mitotic pair is lost: the EW1 neuron.