Insect pheromones

In the pheromone receptors of the sensory cells of the recipient, they produce a nerve stimulus even in very low concentrations, which ultimately leads to a behavioral response.

Male butterflies use a wide range of chemicals as sex pheromones, for example pyrrolizidine alkaloids, terpenes and aromatic compounds such as benzaldehyde.

For example, beekeepers use an artificially produced Nasanov pheromone containing terpenes such as geraniol and citral to attract bees to an unused hive.

It is expected that insect pheromones can also contribute in this way to the control of insect-borne infectious diseases such as malaria, dengue fever or African trypanosomiasis.

[3]The word pheromone consists of the ancient Greek parts of speech φέρειν phérein, überbringen, melden, and ὁρμᾶν hormān, antreiben, erregen.

As early as 1690, Sir John Ray suspected that peppered moths attracted male conspecifics by means of a scent:"It emerged out of a stick-shaped geometer caterpillar: it was a female and came out from its chrysalis shut up in my cage: the windows were open in the room or closet where it was kept, and two male moths flying round were caught by my wife who by a lucky chance were into the room in the night: they were attracted, as it seems to me, by the scent of the female and came in from outside."

– John Ray[17]The French entomologist Jean-Henri Fabre also reported in the mid-19th century on experiments with Saturnia and oak eggar in which females trapped in wire cages attracted hundreds of males within a few days at specific times.

[20] In 1932, the neurophysiologist Albrecht Bethe, who at that time headed the Institute of Animal Physiology at the Goethe University Frankfurt, published an article on an expanded hormone concept in which he distinguished between endohormones and ectohormones.

As an example, Bethe cited the effect of the lactation hormone, which is released by a fetus to its mother and causes the growth of the mammary gland and subsequently the secretion of milk.

"In bees, for example, the workers (i.e. not the mothers) are able to raise a sexually capable queen from an egg or a young larva [...] by special food and transfer of secretions of their salivary glands.

[6] Adolf Butenandt also suspected that communication among insects was based on neurotransmitters, and in the 1940s he began a project to identify the sexual attractant of the domestic silk moth (Bombyx mori).

Using methods common at the time, such as catalytic hydrogenation, melting point determination, and oxidative degradation by potassium permanganate, Butenandt showed that the substance sought was an unsaturated fatty alcohol, (10E,12Z)-10,12-Hexadecadien-1-ol.

"By extraction and condensation experiments, however, it has been convincingly shown that a material principle must be present which is secreted by the female butterflies from scent organs of the last abdominal segments and perceived by the males with their antennae."

– Adolf Butenandt[23]Towards the end of the 1950s, Edward O. Wilson defined substances that trigger the alarm and burrowing behavior of ants as chemical releaser.

To optimize these, the scent-binding proteins in the antennae of females, which play a critical role in detecting oviposition sites, are being intensively studied.

For example, the abdominal glands of the female silkmoth release traces of the (E,E)-isomer of alcohol as well as the analogous (E,Z)-aldehyde bombycal, in addition to the sex pheromone bombycol.

[35] Honey bees possess 15 glands with which they produce and release a number of different substances, thus maintaining a complex communication system based on pheromones.

[38] Biosynthesis of insect pheromones occurs either de novo following the scheme of fatty acid synthesis by successive addition of malonyl-CoA to an initial acetyl or by uptake of precursors from the diet.

[47] Moths such as Utetheisa ornatrix and Tirumala limniace ingest pyrrolizidine alkaloids from food plants such as crotalaria, heliotropium, or Achillea ageratum in the caterpillar, which the adult male converts by oxidation into pheromones such as hydroxydanaidal.

As in the fire beetle, the alkaloids, which are potent feeding poisons and act against predators such as spiders, ants, or net-winged insects, are transferred to females and eggs.

[56] Insect pheromones have a highly species-specific effect, meaning that they elicit the desired behavioral response only in biological specificity but not in individuals of other species.

To ensure specific perception, the pheromone chemical must either be so complex that it does not occur more than once in nature, or the correct ratio of several individual components must trigger the stimulus.

Periplanon B, the sex pheromone of the American cockroach, is an example of a complex single substance to which males respond at extremely low levels of 10−5 nanograms.

The alarm pheromone cocktail of the bedbug contains unsaturated witch and octenaldehydes, which are perceived as a characteristic sweetish odor in bedbug-infested rooms.

[76] Trace pheromones are mainly known in insects living in colonies, which mark their paths with low-volatile substances such as higher molecular weight hydrocarbons.

[83] Brood recognition pheromones are emitted by larvae and pupae and discourage worker bees from leaving the hive while there are still offspring to be cared for.

As early as 1898, Edward Forbush and Charles Fernald made attempts to control the population of the gypsy moth by luring males into traps set with attractant females.

[88] The United States Department of Agriculture continued these attempts in the 1930s, using extracts of female abdominal spikes to attract male moths.

[95] Application of the oviposition-preventing marking pheromone of Rhagoletis cerasi, which cannot be controlled with yellow boards, for example, reduced infestations of cherries by 90%.

A health hazard cannot be generally assessed due to the large chemical diversity of pheromones, but is usually excluded because only small amounts are emitted.