Insect olfaction

[2] For example, olfaction is essential for locating host plants and hunting prey in many species of insects, such as the moth Deilephila elpenor and the wasp Polybia sericea, respectively.

The two organs insects primarily use for detecting odors are the antennae and specialized mouth parts called the maxillary palps.

The evolutionary trade-offs involved require further study because as of 2016[update] most such research has been done under laboratory conditions with unrealistically reliable food.

[8] Sensory neurons in the antenna, maxillary palp, and labella generate odor-specific electrical signals called spikes (action potentials) in response to binding of odors to cell surface proteins like the olfactory receptors.

Specifically the process is as follows: first the odorant wafts towards an insect's antenna or maxillary palp which is covered with hair-like projections called sensilla.

The projection neurons send their axon terminals to a part of the insect brain called the mushroom bodies (important in regulating learned odor responses) and another part of the brain called the lateral horn (important in regulating innate odor responses[3]).

[5] In electroantenograms (EAG) and electropalpograms (EPG) the action potentials from the entire antenna or maxillary palp, respectively, is recorded.

Any of these methods can be combined with a high resolution gas chromatography to isolate volatile compounds from important animals or habitats.

[3] For some agricultural pests manufactured sex pheromones are placed in traps to capture adults before they can oviposit (lay their eggs) leading to the hatching of their destructive larvae.

[5] The art of finding an attractant or repellent for a particular insect of interest is complicated and a long, intensive process.

[5] While CO2 has been found to be an attractant in every arthropod studied[5] and it is very important in mosquito monitoring and control, even this stereotyped reaction can be plastic.