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.

Response of Aphidius colemani to aphid sex pheromone varies depending on plant synergy and prior experience

A critical stage in the success of a parasitoid is the ability to locate a host within its habitat. It is hypothesized that a series of olfactory cues may be involved in altering the parasitoid's movement patterns at this stage of foraging. This paper focuses specifically on host habitat location and host location and the olfactory stimuli necessary to mediate the transition between these stages. Firstly, we confirm the ability of the parasitoid Aphidius colemani to detect the aphid sex pheromone at an electrophysiological level. Following this we investigate the effect of the sex pheromone component (4aS,7S,7aR)-nepetalactone on the movement patterns of A. colemani and its retention within an area. The key findings of this work are that A. colemani is able to detect the sex pheromone components, that parasitoid retention is increased by a synergy of nepetalactone and other host-associated cues and that foraging patterns are augmented by the presence of nepetalactone or experience associated with nepetalactone.

Do asexual morphs of the peach-potato aphid, Myzus persicae, utilise the aphid sex pheromone? Behavioural and electrophysiological responses of M. persicae virginoparae to (4aS,7S,7aR)-nepetalactone and its effect on aphid performance

The aphid sex pheromone component (4aS,7S,7aR)-nepetalactone is considered to be a potential tool for enhancing biological control of aphids. Studies have confirmed its potential to attract parasitoids, increase parasitism rates in the field and also alter the spatial distribution of parasitoids. An important aspect that has been overlooked is the impact that the introduction of nepetalactone may have on aphid populations already present in field or glasshouse environments. The most prevalent pest aphid populations in glasshouse and field environments are the asexual morphs, which are capable of exponential growth if populations are not controlled. The short-term implications of the sex pheromone on asexual aphids were observed through their behavioural response. Using Y-tube olfactometry, it is shown that virginoparae of the peach-potato aphid, Myzus persicae, are repelled by high concentrations of nepetalactone. Long-term effects of the pheromone which may span the aphid's life, or even generations, were assessed via mean relative growth rate (MRGR) and the intrinsic rate of natural increase (rm). Electroantennography also demonstrated that asexual female aphids are able to detect aphid sex pheromone components. To our knowledge, this is the first time it has been reported that M. persicae virginoparae are able to detect aphid sex pheromone components or that their behavioural response and/or performance has been studied. The implications of these results and their significance in understanding semiochemical communication are discussed.