Coleopterous pheromones

Some interesting relationships within groups of coleopterous species, based on subtle differences in structures or mixtures, have been unraveled in the last few years. These and the variety of structures comprising coleopterous pheromones provide a challenging opportunity for the natural products chemist. 

There are more species of Coleoptera than of any other order of insects. It has been estimated that over 350,000 species of beetles have been described, and this order represents about half of the total number of species (l). Thus it is somewhat surprising to discover from recent surveys of the literature (2,3) that pheromones have been identified for only about 50 to 75 species of Coleoptera. In contrast, sex pheromones or sex attractants (most of the latter discovered by screening procedures) are available for over 500 species of Lepidoptera. Furthermore, over half of the known coleopterous pheromones have been isolated and identified from species in the family scolytidae. 

In at least some cases where single component pheromones have been identified the pheromone identification probably can be labeled incomplete. As more research is conducted on the behavior of these species and their interactions with other species, particularly those in the same family and genus, more compounds will undoubtedly be identified that are active in mediating the behavior of these species. At this time I can only reiterate that considerably more research is needed on coleopterous pheromones before we can begin to understand these complex interactive systems. For natural products chemists this should be a fruitful area for investigation for some time. 

Pheromones of insect species in the order Coleoptera are characterized by considerable structural diversity. Unlike the lepidopterous sex pheromones, which are nearly all tatty acid derivatives, coleopterous sex pheromone structures range in complexity from the relatively simple 3,5-tetradecadienoic acid of the black carpet beetle to the tricyclic terpenoid, lineatin, of the striped ambrosia beetle. While the sex pheromones of many beetles consist of mixtures of compounds that act synergistically to elicit a behavioral response, other Coleoptera species appear to use only a single compound for chemical communication between the sexes. In the latter case the compound usually has at least one chiral center and chirality plays a major role in determining pheromone specificity. 

Bark beetles are of great economic importance, which is one of the reasons more research has been done on the pheromones of the Scolytidae than on those of any other family of Coleoptera. Their pheromone systems also seem to be typical of the Coleoptera in that while there is considerable diversity in pheromone structure within this family, there also seems to be a pattern of structures, particularly within a genus. The first pheromone identified from a coleopterous species was from Ips paraconfusus Lanier (then I. confusus) by Silverstein et al. (13). Three compounds — ipsenol (I), ipsdienol (II), and cis-verbenol (III)... 

In this very large coleopterous family the sex pheromone of only two species have been identified. Dlabrotlca vlrglfera vlrgjfera LeConte, the western corn rootworm (VCR), produces and responds to... 

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