Millipede Defensive Compounds Are a Double-Edged Sword: Natural History of the Millipede-Parasitic Genus Myriophora Brown (Diptera: Phoridae)

Toxic defensive secretions produced by millipedes in the orders Julida, Spirobolida, Spirostreptida, and Polydesmida are highly repellent to most vertebrate and invertebrate natural enemies, but a few insects have evolved mechanisms to overcome these defenses. We demonstrate that highly specialized parasitic phorid flies in the species-rich genus Myriophora use volatile millipede defensive compounds as kairomones for host location. Of the two predominant quinone components in the defensive blend of juliform millipedes, 2-methoxy-3-methyl-1,4-benzoquinone alone was sufficient to attract adult flies of both sexes; however, a combination of 2-methoxy-3-methyl-1,4-benzoquinone and 2-methyl-1,4-benzoquinone increased attractiveness nearly threefold. We further discuss oviposition behavior, adult and larval feeding habits, life history parameters, and the potential competitive interactions between phorid flies in the genus Myriophora and other millipede-associated insects.