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Sequence of Pheromone Production

September 1, 2015

The relative proportion of the pheromonal components change during the production period. In analyses of the hindguts of numerous beetles, we have recorded a dis- tinct sequence of production from the time the male beetles land on a tree until pher- omone production ceases.

Methylbutenol and cis-verbenol are present in beetles when they initiate boring and fight resin flow. When the nuptial chamber is formed 2 or 3 days later, ipsdienol and ipsenol are produced. After the gallery is established and the females have started egg laying, the amounts of methylbutenol and cis-verbenol in the hindgut are reduced considerably, whereas ipsdienol and ipsenol are still being produced and verbenone occurs. After 8 to 10 days, all pheromone production ends. Check out human pheromones at http://turkcellgollercepte.com/use-of-human-sex-pheromones/.

Precursors of the Pheromone Components

Cis-verbenol is produced when male beetles are exposed to oleoresin or to oz-pinene. This has been demonstrated in several bark beetles, including Ips species."-3° The source for the biosynthesis of methylbutenol is not known. In I. cembrae, which pro- duce another isomer of methylbutenol,” Renwick and Dickens advanced the hypothe- sis that the precursor of this compound is present in the emerging beetles.“ The pro- duction of methylbutenol may be triggered by juvenile hormone release or by ingestion of a host constituent after feeding is initiated. lpsenol and ipsdienol were not formed in unfed or fed beetles which were exposed to myrcene.“ This differs from results of similar studies with other Ips species.”-33 Ipsdienol and ipsenol are not present in every individual male; the production seems to be limited to beetles exposed to certain un- known conditions.”

HOST-TREE VOLATILES

Host-tree components are assumed by many to provide flying pioneer bark beetles with their main orientation to a suitable habitat for brood production.“ Although beetles should theoretically be able to detect a potential host from a distance by olfactory means, Moeck found that host discrimination in most bark beetles associated with Pinus ponderosa occurs after the beetles have landed on a tree.” Learn about human pheromones at http://www.doniejnalezymyodniejzalezymy.eu/more-about-human-pheromones.html.

Host-tree monoterpenes act as synergists for the aggregating pheromone in several bark beetle species.“ In I. typographus, ozpinene and other monoterpenes attract the beetle,“ but repellent effects have also been reported." In a mixture of ipsdienol and the verbenol isomers, we found apinene to be synergistic.“ In the presence of methlylbutenol, however, both apinene and other host-tree components failed to enhance attraction.” Whether there are any synergistic host components or not remains unanswered.

Pheromones produced by bark beetles are utilized by predators and parasites to locate habitats of their prey and therefore are often kairomones.  The predator clerids, Thanasimu formicarius (L.) and T. femoralis (Zett.). are attracted to the syn- thetic pheromone components of I. typographus.“ lpsenol and ipsdienol are the main kairomones for T. formlcarius

Both females and males respond to the artificially produced pheromone. lt has not been possible to demonstrate a significant difference in attraction of the sexes to any combination of the pheromone components. The sex ratio varies among beetles trapped during the flight period and at different localities. Females predominate, with ratios generally between 1.5 and 3.0. Higher ratios have also been found.

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