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 tha t the non-ball-rolling dung beetle Pachylomerus fem oralis (K irby) rolled the flesh-covered seeds from the fruit o f the spineless m onkey orange tree, Strychnos madagascariensis Poiret, an investigation into the chemical a ttrac tan ts o f this fruit was made. U sing headspace gas chrom atography with electroantennographic and flame ioni­ zation detection in parallel, followed by G C-M S analysis, 1-butanol, methyl bu tanoate , ethyl 2-m ethylpropanoate, ethyl bu tanoate , butyl ethanoate, ethyl 2-m ethylbutanoate, propyl b u ta ­ noate, butyl p ropanoate , m ethyl hexanoate, butyl 2-m ethylpropanoate, and butyl bu tanoate were identified as the constituents o f the attrac tan t. It was found that P. fem oralis beetles were a ttracted to a m ixture o f the synthetic com pounds about as strongly as to the fresh fruit. The beetles were also equally a ttrac ted to the fruit and to horse dung in areas where ripe fruit was not available. In areas perm eated with the smell o f the ripe fruit the horse dung retained its attractiveness, whereas no beetles were caught in traps baited with fruit.