Pharmacophagy in green lacewings (Neuroptera: Chrysopidae: Chrysopa spp.)?

Jeffrey R Aldrich; Kamal Chauhan; Qing-He Zhang

doi:10.7717/peerj.1564

Pharmacophagy in green lacewings (Neuroptera: Chrysopidae: Chrysopa spp.)?

PeerJ. 2016 Jan 18:4:e1564. doi: 10.7717/peerj.1564. eCollection 2016.

Authors

Jeffrey R Aldrich¹, Kamal Chauhan², Qing-He Zhang³

Affiliations

¹ Associate, Department of Entomology & Nematology, University of California , Davis, CA , United States.
² Invasive Insect Biocontrol and Behavior Laboratory, United States Department of Agriculture-Agriculture Research Service , Beltsville, MD , United States.
³ Director of Research, Sterling International, Inc , Spokane, Washington , United States.

Abstract

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 oculata Say, which is released from thousands of microscopic dermal glands on the abdominal sterna. Iridodial-baited traps attract C. oculata and other Chrysopa spp. males into traps, while females come to the vicinity of, but do not usually enter traps. Despite their healthy appearance and normal fertility, laboratory-reared C. oculata males do not produce iridodial. Surprisingly, goldeneyed lacewing males caught alive in iridodial-baited traps attempt to eat the lure and, in Asia, males of other Chrysopa species reportedly eat the native plant, Actinidia polygama (Siebold & Zucc.) Maxim. (Actinidiaceae) to obtain the monoterpenoid, neomatatabiol. These observations suggest that Chrysopa males 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, although C. oculata males 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 wild C. oculata males collected in early spring contained traces of this dihydronepetalactone. These findings are consistent with the hypothesis that Chrysopa males feed on oviparae (the late-season pheromone producing stage of aphids) to obtain nepetalactol as a precursor to iridodial. In the spring, however, wild C. oculata males produce less iridodial than do males collected later in the season. Therefore, we further hypothesize that Asian Chrysopa eat A. polygama to obtain iridoid precursors in order to make their pheromone, and that other iridoid-producing plants elsewhere in the world must be similarly usurped by male Chrysopa species to sequester pheromone precursors.

Keywords: Aphid; Chrysopa; Chrysopidae; Green lacewings; Iridodial; Neuroptera; Pharmacophagy; Pheromone; Predator; Sequestration.

Grants and funding

Most of the research was performed at the USDA-ARS laboratory in Beltsville, MD, when Dr. Aldrich was a Research Entomologist with this agency. Dr. Qing-He Zhang was a postdoctoral Research Associate with Dr. Aldrich at this time (∼2002–2003). The USDA-ARS provided funding in the form of salaries, and laboratory space and supplies, but funders did not have a role in the research other than broad National Program guidelines. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.