Pharmacophagy in green lacewings (Neuroptera: Chrysopidae:Chrysopaspp.)?

Green lacewings (Neuroptera: Chrysopidae) are voracious predators of aphids and other small, soft-bodied insects and mites. Earlier, we identified (1R,2S,5R,8R)-iridodial from wild males of the goldeneyed lacewing,Chrysopa oculataSay, which is released from thousands of microscopic dermal glands on the abdominal sterna. Iridodial-baited traps attractC. oculataand otherChrysopaspp. males into traps, while females come to the vicinity of, but do not usually enter traps. Despite their healthy appearance and normal fertility, laboratory-rearedC. oculatamales do not produce iridodial. Surprisingly, goldeneyed lacewing males caught alive in iridodial-baited traps attempt to eat the lure and, in Asia, males of otherChrysopaspecies reportedly eat the native plant,Actinidia polygama(Siebold & Zucc.) Maxim. (Actinidiaceae) to obtain the monoterpenoid, neomatatabiol. These observations suggest thatChrysopamales must sequester exogenous natural iridoids in order to produce iridodial; we investigated this phenomenon in laboratory feeding studies. Lacewing adult males fed various monoterpenes reduced carbonyls to alcohols and saturated double bonds, but did not convert these compounds to iridodial. Only males fed the common aphid sex pheromone component, (1R,4aS,7S,7aR)-nepetalactol, produced (1R,2S,5R,8R)-iridodial. Furthermore, althoughC. oculatamales fed the second common aphid sex pheromone component, (4aS,7S,7aR)-nepetalactone, did not produce iridodial, they did convert ∾75% of this compound to the corresponding dihydronepetalactone, and wildC. oculatamales collected in early spring contained traces of this dihydronepetalactone. These findings are consistent with the hypothesis thatChrysopamales feed on oviparae (the late-season pheromone producing stage of aphids) to obtain nepetalactol as a precursor to iridodial. In the spring, however, wildC. oculatamales produce less iridodial than do males collected later in the season. Therefore, we further hypothesize that AsianChrysopaeatA. polygamato obtain iridoid precursors in order to make their pheromone, and that other iridoid-producing plants elsewhere in the world must be similarly usurped by maleChrysopaspecies to sequester pheromone precursors.