Olfactory aposematism

When disturbed or molested, these insects release small droplets of hemo-lymph from the tibio-femoral joints of their legs, and it is now well established that the deterrency exhibited by many species of coccinellids towards potential predators results from the presence of repellent and bitter alkaloids in that fluid [ 12,13]. In ladybirds, this unpalatability is associated with a bright aposematic coloration and a characteristic smell due to 3-alkyl-2-methoxypyrazines [14, 15]. The beetles use these molecules not only to reinforce the visual alerting signal on an olfactory level, but also as aggregation pheromones [16]. 

Olfactory aposematism (Eisner and Grant, 1981) means associating an odor by conditioning (experience) with an odorless toxin such as nicotine, morphine, or strychnine. This is probably widespread among mammals. First the animal tastes the plant and finds it either impalatable or suffers ill effects. After that. 

Two speculative possibilities relate to olfactory aposematism. The first is whether there are non-toxic plants that smell or taste like toxic ones. In other words, do plants practice Batesian mimicry. Such mimicry is unlikely, as mammalian herbivores constantly sample plants and thereby test for favorable and adverse effects of eating a particular species. Furthermore, given the keen sense of smell of mammals, two plant species would have to exactly smell alike for mimicry to work. Second, do two distasteful or toxic plant species smell or taste alike so that herbivores can more easily classify dangerous plants and avoid them (Mullerian mimicry) (Eisner and Grant, 1981 Lindroth, 1988 Augner and Bernays, 1998). 

Olfactory aposematism association of food toxicity with naturally occurring odor, journal of Chemical Ecology 11,1289-1295. 

Eisner, T. and Grant, R. P. (1981). Toxicity, odor aversion and olfactory aposematism. Science 213,213-476. 

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