The Christmas season brings to our attention stories related to religious events. The Christian Christmas story includes the tale of Wisemen bearing gifts for Baby Jesus that include olibanum, described in the Bible as, Frankincense. Frankincense was named after the Franks who introduced it to Western Europe upon return from the crusades. Frankincense is a resin produced by trees in the genus, Boswellia, that are found in East Africa and other parts of the Middle East. The resin has been traded by humans for over 5000 years. The resin produces a fragrant odor when burned as incense. Charred Frankincense (Kohl) was historically used by Egyptians as an eyeliner.
At least 8 species of Boswellia are considered endangered and this has an effect on Frankincense production. There are several stresses on the habitat for Boswellia that are leading to its decline. These include livestock grazing, fire and methods of resin collection that damage the tree. In some areas, the longhorn beetle, Idactus spinipennis, is associated with death of Boswellia. Idactus spinipennis was first described in an 1890 survey of African beetles by Charles J Gahan. Gahan described the taxonomic characteristics of this handsome longhorn beetle, but had little to say about its biology. em>Idactus spinipennis will lay eggs and feed on living Boswellia trees.
Attacks by beetles and other wood boring insects are a major reason why trees produce resins. Healthy trees use the resins for defense. As a beetle bores a hole in a tree to establish a feeding site, secretion of resin by the tree can immobilize the beetle, kill it or pitch it out of the tree. We can probably blame wood boring beetles in general (though not specifically, Idactus spinipennis) as the reason for resin production by these trees. Absent the history of attack by beetles, the trees would have little reason to produce resin and thus, we would not have Frankincense. Thus, it is fair to blame the beetles that resin production and Frankincense exists.
It may be less fair to blame the beetles for the decline in the tree population. When trees are stressed by drought or overwhelmed with damage, they may not be able to produce enough resin to mount an effective defense. Do beetles damage and kill healthy trees? Or do beetles only successfully attack and kill trees that are stress and dying? If the beetles are killing otherwise healthy trees, then efforts to manage beetle populations could help preserve trees. If however, the beetles are only attacking trees that are in decline, then managing the beetles would have little effect. Efforts would be better devoted to other factors that stress the trees.
Like many endangered species, preservation of habitat, in this case limiting grazing by animals and suppressing fire may be necessary to maintain a healthy Boswellia population for incense production. It is premature to Blame the Beetle for the decline.