Convergent evolution: What do cats, catnip, aphids, and mosquitoes have in common?

The well-known English naturalist John Ray wrote more than 200 years ago about the curious reaction of cats to a plant in the mint or Lamiaceae family, the catnip plant . Ray even wrote a short verse about the relationship between cats and catnip: 'If you set it the cats will eat it; If you sow it the cats can't know it' (Considine 2016). When leaves of this plant are bruised and release their volatiles, cats react by attempting to rub and roll over on the leaves, seeming to be in a state of ecstasy. The movements are stereotyped and usually culminate in the cats rubbing their faces on the plant, licking their fur, and rolling on the plant. Not only household felines but even lions tested by McElvain at the Wisconsin Zoo showed the same stereotyped reaction (McElvain et al. 1942). Samuel McElvain and Jerry Meinwald demonstrated that the active constituent of was nepetalactone, an iridoid alkaloid (Tucker and Tucker 1988). Thomas Eisner (1964) suggested that nepetalactone and related compounds might be anti-herbivory compounds in plants since his experiments with several insect species suggested a strong aversive reaction to them. Eisner (1964) also noted that several insects produce the same or similar iridoid alkaloids and remarked on possible convergent evolution. Todd (1962) did a survey of cats in Boston and determined that the responsiveness to nepetalactone was inherited as autosomal dominant. Hart and Leedy (1985) determined that the feline reaction was through the olfactory pathway and not the vomeronasal pathway, unlike cat and lion pheromones, which activate the vomeronasal organ (VMO) and elicit the very characteristic and stereotyped 'flehmen' response, which consists of a wrinkled nose and a gaping mouth to ensure that the pheromone molecules enter theVMOwhose openings are in the mouth. The catnip response has certainly evoked much unconventional research.