Attractants

natural or synthetic substances that attract animals. Insects are especially sensitive to attractants. Three basic types of attractants are known: sexual attractants, which attract the way that members of the opposite sex do; food attractants, which attract the way food does; and attractants which attract like a substratum for egg-laying. The sexual attractants are the best known. It has been established that substances extracted from the females of some insect species in a concentration of 1 x 10^-14 mg per liter of air attract males of the same species, and sometimes those of other genetically close species. Cases have been observed in which butterflies are attracted from a distance of 3 to 9 km. The presence of attractants has been established in more than 300 insect species. For some of them the attractants have been extracted and their structures have been studied—for example, the attractant of the gypsy moth gyp-tol (formula 1).

In order to attract the gypsy moth, the synthetic product gyplur (formula 2) can also be used. It is a homologue of gyptol and trimedlur (tributyl ester 4- [or 5-] chlor-2- methyl-cyclohexane carbonic acid [formula 3]) from the eastern fruitfly.

Attractants are of practical use in fighting plant pests and animal parasites. Using the attractants as bait, one can exterminate the insects with a minimal waste of insecticides; it is also possible to disorient the males and thus reduce the numerical size of the following generations. Attractants are also used for determining which harmful insects have infected a crop.