Observations on the Association between Some Buprestid and Cerambycid Beetles and Black Frankincense Resin Inducement

Hilary Sommerlatte,Ben-Erik Van Wyk

doi:10.3390/d14010058

Abstract

Samburu resin harvesters in northern Kenya maintain that frankincense resin flow from Boswellia neglecta and Commiphora confusa is induced by insect larval activity. Observations on the insects’ larval behaviour support these claims. During the frankincense harvest, buprestid beetle larvae, identified as a Sphenoptera species, are found under B. neglecta resin, eating the monoterpene-rich inner bark, which apparently stimulates the trees to produce copious amounts of fresh resin. The same behaviour was observed with cerambycid beetle larvae, identified as Neoplocaederus benningseni Kolbe, on C. confusa trees. Remarkably, these insects have developed the capacity to digest the resin-saturated inner bark and overcome the toxic, repellent characteristics of oleo-monoterpenes. The frankincense resin also appears to act as a protective covering during the insects’ larval and pupal stages. Excessive tree damage was not noted from these insect invasions. Even though the tree species are from different genera, the resin produced by both is black, with a very similar aromatic chemical profile. The question thus arises as to whether the larval feeding behaviour of these beetle species has an influence, not only on the physical appearance but also on the chemical composition of the resins.

Highlights

There are two tree species in northern Kenya that produce monoterpenoid frankincense resins of commercial importance [1]
We examined 240 C. confusa trees in 6 different locations, during a resource assessment conducted by the first author
The buprestid beetle larva associated with B. neglecta was identified as a Sphenoptera species (Coleoptera: Buprestidae), and the cerambycid larva and adult beetle associated with C. confusa, as Neoplocaederus benningseni Kolbe (Coleoptera: Cerambycidae)

Summary

Introduction

There are two tree species in northern Kenya that produce monoterpenoid frankincense resins of commercial importance [1]. The second type of resin is black and resembles sticky tar It is produced in much bigger quantities and is harvested for commercial purposes [1]. The first type is similar to that of B. neglecta, whereby pale-yellow, aromatic frankincense resin droplets exude spontaneously from the surface of the bark, without there being any notable damage to the bark’s surface. This is used as a chewing gum by Samburu collectors and is harvested and sold as frankincense. The third type is an aromatic, black resin that is harvested and sold as frankincense [1] It contains α-pinene, α-thujene, β-pinene, terpinen-4-ol, and p-cymene as major volatile constituents [1]

Methods

Discussion

Conclusion