Fig. 5. Antennal distribution of the sensillum types identified. (A) Frontal view of a Drosophila head. The olfactory organs, antennae (above) and maxillary palps (below), are marked in green. (B) Schematic drawing of the Drosophila third antennal segment's posterior and anterior face. LB, large s. basiconica region; A, arista; S, sacculus entrance; ST, s. trichodea region. The locations of the different sensillum types investigated are indicated by coloured circles (corresponding to the colours in Fig. 4). The total number of each sensillum type encountered is indicated in parentheses. Circles with a black dot in the centre represent investigation with GC—SC methodology, while open circles were characterised by stimulation with synthetic compounds.