The antennal lobe is the primary (first order) olfactory brain area in insects.
The antennal lobe is a sphere-shaped deutocerebral neuropil in the brain that receives input from the olfactory sensory neurons in the antennae and mouthparts.
In insects, the olfactory pathway starts at the antennae (though in some insects like Drosophila there are olfactory sensory neurons in other parts of the body) from where the sensory neurons carry the information about the odorant molecules impinging on the antenna to the antennal lobe.
[2] Each olfactory sensory neuron expresses a single odorant receptor type and targets the same glomeruli as other olfactory sensory neurons expressing that receptor type, such that each glomeruli houses all or the majority of sensory neurons of a given receptor type.
[5] The local neurons, which are primarily inhibitory, have their neurites restricted to the antennal lobe.