Semiochemicals of the Scarabaeinae, III: Identification of the Attractant for the Dung Beetle Pachylomerus femoralis in the Fruit of the Spineless Monkey Orange Tree, Strychnos madagascariensis

Following the observation that the non-ball-rolling dung beetle Pachylomerus femoralis (Kirby) rolled the flesh-covered seeds from the fruit of the spineless monkey orange tree, Strychnos madagascariensis Poiret, an investigation into the chemical attractants of this fruit was made. Using headspace gas chromatography with electroantennographic and flame ionization detection in parallel, followed by GC-MS analysis, 1-butanol, methyl butanoate, ethyl 2-methylpropanoate, ethyl butanoate, butyl ethanoate, ethyl 2-methylbutanoate, propyl butanoate, butyl propanoate, methyl hexanoate, butyl 2-methylpropanoate, and butyl butanoate were identified as the constituents of the attractant. It was found that P. femoralis beetles were attracted to a mixture of the synthetic compounds about as strongly as to the fresh fruit. The beetles were also equally attracted to the fruit and to horse dung in areas where ripe fruit was not available. In areas permeated with the smell of the ripe fruit the horse dung retained its attractiveness, whereas no beetles were caught in traps baited with fruit.