Pleasing fungus beetles living partly concealed in their fungal food source have devised a chemical arsenal that keeps predators and competitors at bay. Almost a dozen small, highly volatile compounds have been identified in glandular secretions near its front legs and reflex blood from its abdomen. Glandular secretions are thought to play predominantly antimicrobial functions whereas the malodorous reflex blood compounds deter competitors and predators, such as ants and rodents, while defending against microbial pathogens.
Sites of two types of secretions (left). Beetles living on fungus (right) Artist: Meghan Hanson || Copyright: All rights reserved by Biomimicry 3.8 Institute.
“First insights into the chemical defensive system of the erotylid beetle, Tritoma bipustulata reports the previously hardly known ability of abdominal reflex bleeding in this coleopteran family…The different secretions were dominated by aromatic compounds; in addition, we detected alkenes, ketones, organic acids as well as a single sesquiterpene. The majority of these detected compounds had strong antimicrobial properties in microbiological assays with entomopathogenic micro-organisms.” (Drilling and Dettner 2010: 243).
“Adults of Tritoma bipustulata responded to disturbance by emitting secretion from their pronotal glands. A clear, odourless fluid was released on disturbance; it spread over the pronotum and evaporated rapidly…when considerably disturbed directly at the abdominal tip, a clear, malodorous and highly volatile secretion was discharged from this body region.” (Drilling and Dettner 2010: 246)
“The pronotal secretion compounds, benzyl alcohol and benzothiazole, significantly deterred ants from feeding…indole as well as 3-methylindole were detected; both compounds significantly deterred ants from feeding…In agar diffusion tests, almost all tested compounds were significantly antimicrobial… 3-Methylindole, indole, p-cresol and benzothiazole had the strongest effects on the tested microorganisms.” (Drilling and Dettner 2010: 247)
“The volatile compounds identified from these defensive devices were shown to deter ants from feeding and to inhibit growth of entomopathogens” (Drilling and Dettner 2010: 248).
“The presence of such malodorous compounds in the abdominal reflex blood might also irritate fungus-feeding mammals, since in European forests many ground squirrels and microtine rodents are extensively mycophagous.” (Drilling and Dettner 2010: 251)