The adult antennal lobe is a bilaterally paired synaptic neuropil domain of the deuterocerebrum lying in front of the protocerebral synaptic neuropil domains. It is divided into approximately 50 glomeruli and is clearly separated from adjacent neuropil domains by an extensive glial sheath. The two antennal lobes are connected by the antennal commissure and receive olfactory receptor neuron axons from the antennal nerve and subesophageal tract. It is also connected to the antenno-cerebral tracts and the broad root.