Fig. 1. Selective ablation of sensory neurones. (A-D) Dorsal is upwards and anterior towards the right. (A) Detail of the sensory neurones revealed by GAL4 line C161 driving expression of UAS-CD8GFP in a living third instar larva. Eleven sensory neurones of the dorsal and lateral clusters in the mesothorax. The two clusters are separated by the dorsal bipolar dendrite neurone (dbd). The lateral group, ventral to dbd, consists of four multidendritic neurones (ldaA, ldaB, ldaC and ldaD). The dorsal cluster, dorsal to dbd, consists of six neurones, including two chordotonal neurones (dch1 and dch2), and four multidendritic neurones (ddaA, ddaB, ddaC, ddaD). (B) Detail of the lateral cluster and dbd in a live specimen prior to laser ablation. (C) The same neurones as shown in B 12 hours after laser ablation of the four neurones ventral to dbd. One of the neurones is missing (*) and the other three neurones exhibit a condensed cell body, loss of dendrites and blebbing. (D) The same neurones 30 hours after ablation, only 2 neurones are visible and exhibit shrunken morphology and no dendritic structures. (E) Central projections of the neurones in line C161 revealed immunocytochemically with anti-GFP. The panel shows a dorsal view of the mesothoracic neuromere of the ventral nerve cord of a pupa 48 hours after unilateral laser ablation of the neurones in the dorsal and lateral cluster neurones. On the intact (right-hand) side the normal pattern of central projections is seen in which it is possible to identify three major axon pathways (med, lt and dpt). On the ablated (left-hand) side there are no central projections evident (arrow). (F) Dorsal view of the mesothoracic neuromere 48 hours after ablation of only the lateral cluster neurones. On the intact (right-hand) side the normal pattern of axons is present. On the ablated (left-hand) side only the med projection is evident. Scale bar: 50 µm.