While snakes have them on the roof of their mouths.
Insects have olfactory sensors on their
wings
feet
O antennae
tongue

The majority of olfactory receptor neurons typically reside in the antenna. These neurons can be very abundant, for example Drosophila flies have 2,600 olfactory sensory neurons. Insects are capable of smelling and differentiating between thousands of volatile compounds both sensitively and selectively.

Here’s a link to where I found the information if I wasn’t helpful — https://en.m.wikipedia.org/wiki/Insect_olfaction

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