Posted on: 02 March, 2017
Author: Alexander P
When entomologists and chemists originally collaborated to tackle the problem of isolating the top pheromones, they assumed that they were searching for a single compound for each species. How wrong t... When entomologists and chemists originally collaborated to tackle the problem of isolating the top pheromones, they assumed that they were searching for a single compound for each species. How wrong they were! The first successful identication of scolytid pheromones in I. paraconfusus disclosed not one but three compounds (Silverstein et al. 1966) which act together to attract both sexes to a newly attacked host (Wood et al. 1968) (table 8.1). Moreover, it is now apparent that some pheromone compounds are shared by more than one species (table 8.1). Another exciting and fundamental discovery was that female Dendroctonus breviomis produce primarily one pheromone compound, brevicomin* (Silverstein et al. I968), while the responding males produce another, frontalin (Kinzer et al. 1969), both of which are active in the aggregation process (Vité and Pitman 1969). Finally, it was discovered that the host tree may also contribute volatile components to the chemical message (Bedard et al. 1969; Pitman 1969; Bedard et al. 1970). Thus, rather than to refer just to aggregating pheromones, it is more appropriate to speak about the top pheromones. The male brush-organs, hair-pencils and coremata originally evolved. Miriam Rothschild proposed the idea (quoted in Birch 1970c) that insect attractants and courtship pheromones evolved in connection with food plant odors according to http://thongchaimedical.org/understanding-female-sex-pheromones/ A character fulfilling the double function of linking owers and pollinators in time and space would have a much better chance of selection than one with a single benecial attribute. Their role as courtship pheromones would have subsequently diverged and developed from this and the odors strengthened to function both as courtship pheromones and possibly as deterrents to other species pheromones. Brower (1963) suggested that a complex male scent apparatus was more likely to develop in those species or groups where visual signals are reduced or confusing, such as Miillerian mimics, in order to overcome the potential difficulty of visual recognition between species pheromones. This may be one way in which selective pressures would encourage the development of scent-organs. However, Vane-Wright (1972) points out that many Miillerian groups lack a complex scent apparatus whereas several sex-limited mimics do have scent-organs. There is clearly no universal evolutionary route towards scent-organs and no simple connection between their presence or absence and the ability to become sexually dimorphic, polymorphic or mimetic in any particular fashion. Visual information might indeed be confused or minimal in the nocturnal Lepidoptera, though, as noted, scent-organs are certainly not universal for these families nor are they known to be involved in species recognition. It seems equally feasible that they should have been selected for as pheromone deterrents. The behavior in such a way that they are clearly within the category — aphrodisiac pheromones. There is a distinct group of pheromones which mediate behavior patterns immediately prior to copulation. They are sex pheromones, i.e., produced by either the male or the female, but in contrast to the female sex attractant pheromones, they are employed after the sexes have been brought together. Such close-range pheromones may evoke a direct copulatory attempt or they may initiate a different behavioral response, such as feeding or inhibition of locomotion, which itself facilitates copulation. Source: Free Articles from ArticlesFactory.com Alexander P is a blogger that studies pheromones and lives in Los Angeles, CA.