Pheromone-Specific Processing System in the Female American Cockroach

macroglomerular complex; PN: projection neuron. H.N. and M.I. contributed equally to this work. 2 Many animals depend on pheromone communication for successful mating. Sex pheromone in insects is usually released by females to attract males. In American cockroaches, the largest glomerulus (B-glomerulus) in the male antennal lobe (first-order olfactory centre) processes the major component of sex pheromone. Using intracellular recordings combined with fine neuroanatomical techniques, we provide evidence that the female homolog of the male B-glomerulus also acts as a sex pheromone-specific detector. Whereas ordinary glomeruli that process normal environmental odours are innervated by single PNs, the B-glomerulus in both sexes is innervated by multiple PNs, one of which possesses a thicker axon, termed here B-PN. Both soma size and axon diameter were smaller on B-PNs from females compared to B-PNs from males. The female B-PNs also produce fewer terminal arborisations in th