Chemical mimicry (or molecular mimicry) is a type of biological mimicry involving the use of chemicals to dupe an operator. 
A chemical mimic dupes an operator (e.g. a predator) by showing an adaptive chemical resemblance to an object of its environment and as a consequence receives selective advantage. In all cases of chemical mimicry it has been found that the mimicking species is the only species to benefit from the reaction with either costs or no effect on the duped species. 
This is by adapting to produce chemicals (ex: allomones, pheromones, odours, etc.) that will cause a desirable behavioural reaction in the species being deceived and a selective advantage to the mimic, as in ant mimicry. Chemical mimicry exists within many of the different forms of mimicry such as aggressive, protective, Batesian, and Müllerian mimicry and can involve a number of different senses. 
Mimicking semiochemicals make up some of the most widely used forms of chemical mimicry, but is less apparent than more visual forms. As a result, this topic has been relatively neglected in research and literature. 
Two examples of organisms displaying chemical mimicry are the mimicking of Noctuid pheromones by bolas spiders to lure prey and the duping of insects within their own nests by mimicking their odours in order to enter and hide within the nest undetected.