J Chem Ecol (2009) 35:1181–1187 DOI 10.1007/s10886-009-9701-x Prothoracic Gland Semiochemicals of Green Lacewings Jeffrey Richard Aldrich & Thanh C. Le & Qing-He Zhang & Jorge Torres & Shaun L. Winterton & Baoyu Han & Gary L. Miller & Kamlesh R. Chauhan Received: 26 June 2009 /Revised: 18 September 2009 /Accepted: 24 September 2009 /Published online: 22 October 2009 # U.S. Government 2009 Abstract Adult chrysopids have paired prothoracic glands oculata, Co. nigricornis, Co. incompleta, Co. quadripunc- (PG) that are thought to produce defensive secretions tata (USA), and Co. septempunctata (China); Chrysoperla (allomones). We analyzed PG extracts of the following green (= Cl.) rufilabris (USA) and Cl. sp. (Brazil); Plesiochrysa lacewings from North and South America, Australia, and ramburi and Mallada spp. (Australia). PG secretions are China: Ceraeochrysa cubana (Brazil); Chrysopa (=Co.) characteristic for species within a genus, except for Chrysopa spp. (Z)-4-Tridecene is ubiquitous, but (Z,Z)-4,7-tridecadiene is a major PG constituent in some Chrysopa spp. and in P. ramburi. Earlier reports that Co. oculata and Co. nigricornis Mention of commercial products does not constitute an endorsement produce 1-tridecene were shown to be in error. Chrysopa PG by the USDA secretions are distinguished by the presence or absence of N- J. R. Aldrich (*) : T. C. Le : K. R. Chauhan 3-methylbutylacetamide, plus skatole (3-methylindole). Ska- USDA-ARS Invasive Insect Biocontrol & Behavior Laboratory, tole is also identified for the first time from the Plesiochrysa 10300 Baltimore Avenue, Bldg. 007, rm301, BARC-West, and Ceraeochrysa. The PG secretion in Plesiochrysa Beltsville, MD 20705, USA e-mail: [email protected] ramburi is characterized by the presence of (Z)-4-undecene instead of (Z)-4-tridecene, and N-3-methylbutylpropanamide Q.-H. Zhang instead of the acetamide, resembling the PG secretions of Sterling International, Inc., Chrysopa nigricornis, Co. septempunctata and Co. incom- 3808 N. Sullivan Road, Bldg. 16P, Spokane, WA 99216, USA pleta. The chemotaxonomic value of PG semiochemicals is discussed, including evidence for subgroups within the genus J. Torres Chrysopa as it now stands. DEPA-Entomologia, Universidade Federal Rural de Pernambuco, Av. Dom Manoel de Medeiros, s/n - Dois Irmãos, . 52171-900 Recife, PE, Brasil Keywords Pheromone Allomone Tridecene Skatole Iridodial . Amide . Chemotaxonomy. Predator . S. L. Winterton Biosynthesis . Neuroptera . Chrysopidae Department of Primary Industries & Fisheries, Entomology Collection, 80 Meiers Road, Indooroopilly, Queensland 4068, Australia Introduction B. Han Tea Research Institute of Chinese Academy of Agricultural Sciences, Green lacewing larvae are voracious predators of small soft- Hangzhou 310008, People’s Republic of China bodied arthropods, such as aphids and mites, and are sold commercially, principally for aphid control in greenhouses G. L. Miller (Stelzl and Devetak 1999;McEwenetal.2001; Henry and USDA-ARS Systematic Entomology Laboratory, 10300 Baltimore Avenue, Bldg. 005, rm17, BARC-West, Wells 2007). In some chrysopid genera, the adults are also Beltsville, MD 20705, USA predacious (e.g., Chrysopa), but many adult green lacewings 1182 J Chem Ecol (2009) 35:1181–1187 (e.g., Chrysoperla) subsist on only nectar and pollen (Brooks Methods and Materials and Barnard 1990). Green lacewing adults have long been known to commu- Insects and Preparation of Extracts The sources, method of nicate intraspecifically via substrate vibrations (e.g., Henry sampling the adult insects, identity, and the specialists 1982), but only recently was it discovered that males in the responsible for identifying the lacewings are listed in genus Chrysopa produce aggregation pheromones from Table 1. Identifications were aided by reference to Penny thousands of elliptically shaped glands embedded in their et al. (2000) and Brooks and Barnard (1990). Traps used to abdominal cuticle (Chauhan et al. 2004; Zhang et al. 2004, catch live chrysopids were modeled after a previously 2006a, b). Interestingly, female goldeneyed lacewings described trap (Aldrich et al. 1984). Iridodial lures were [Neuroptera: Chrysopidae: Chrysopa (= Co.) oculata Say] prepared as described before (Chauhan et al. 2007), except do not enter traps baited with pheromone (1R,2S,5R,8R- that octane was used as solvent instead of heptane. The iridodial) (Chauhan et al. 2004; Zhang et al. 2004), plant volatile lure was prepared in an analogous manner presumably because females attract males via substrate- using β-caryophyllene/ 2-phenylethanol/ methyl salicylate borne vibrations at close range (Henry 1982). However, (1:1:1 by volume; total active ingredient=5 mg). Chemical Chauhan et al. (2007) showed that significant numbers of wild extracts were prepared in ca. 50 μl of methylene chloride Co. oculata females are attracted to the vicinity of iridodial (EMD Chemicals Inc., Gibbstown, NJ, USA) by either dispensers in the field, and observed that the attracted females extracting the whole thorax (earlier samples) or by excising laid eggs on soybean leaves near the dispensers. Thus, the the glands from the prothorax (later samples). The paired judicious application of Chrysopa pheromones may provide a prothoracic glands were easily removed by fastening a practical means to conserve and augment these lacewings in lacewing, dorsal side up, under water in a dissecting dish, the field for biological control of pests. transversely cutting the dorsal intersegmental membrane All adult chrysopids possess paired prothoracic glands between the prothorax and mesothorax, and making a (PG) thought to produce defensive secretions (allomones) dorso-medial incision in the prothorax exposing the bluish- (Güsten and Dettner 1991; Szentkirályi 2001). In the course colored glands in each side of the prothorax. Each gland, of ongoing research efforts to find aggregation pheromones attached to a small piece of cuticle, was then removed with for other chrysopid species, we have investigated or fine forceps, gently dried with tissue paper, and extracted in reinvestigated the PG secretions of ten species from five about 20 μl of solvent (CH2Cl2 or hexane) for analysis. genera in the tribe Chrysopini. Blum et al. (1973)identified skatole (3-methylindole) as the compound responsible for the Chemical Standards The following commercially available stench of adult goldeneyed lacewings (Co. oculata), with the standards were used: 1-tridecene, hexanoic acid, octanoic acid, major non-odorous (to humans) component of the secretion skatole, 3-hexanol, 2-hexanol, tridecanol, benzaldehye, 2- (93%) reportedly being 1-tridecene. The presence of skatole phenylethanol, methyl salicylate (Aldrich Chemical Co., in PG secretions of Chrysopa spp. was verified by Güsten Milwaukee, WI, USA); nonanoic acid (Emery Industries, and Dettner (1991), but these authors found (Z)-4- Cincinnati, OH, USA); nonanal, decanal, and β- tridecene in species representing five genera of Chrys- caryophyllene (Bedoukian Research, Danbury, CT, USA). N- opini, including six Chrysopa species. However, Güsten 3-Methylbutylacetamide and N-3-methylbutylpropanamide and Dettner (1991) did not include spectral data or were prepared by reactions of 3-methylbutylamine with acetyl chemical details as to how the double bond position and and propanyl chlorides, respectively, at 0°C in the presence of geometry of tridecene were determined. More recently, triethylamine (Heath and Landolt 1988). (Z,Z)-4,7-Trideca- Zhu et al. (2000) identified (Z)-4-tridecene as the sole diene was synthesized starting with a −78°C suspension of major constituent of the PG secretion in Cl. carnea,but hexyltriphenylphosphonium bromide (1.04 g, 2.44 mmol) in they also described the secretion as “offensive-smelling”, 20 ml of THF to which a 1M THF solution of lithium bis which is enigmatic since skatole was not present and (trimethylsilyl)amide (2.3 ml, 2.3 mmol) was added. The tridecenes are not strong or foul smelling. reaction mixture was warmed to −30°C over 30 min, kept at Here, we report on analyses of PG secretions for the this temperature for 1 h, and then cooled to −78°C. To this following green lacewings from North and South clear orange ylide solution, a 0.5 ml THF solution of (Z)-3- America, Australia, and China: Ceraeochrysa (= Ce.) hepten-1-al [112 mg, 1 mmol; prepared by Swern oxidation cubana (Hagen) (Brazil); Chrysopa (=Co.) oculata Say, (Chauhan et al. 1994)of(Z)-3-heptene-1-ol] was added. The Co. nigricornis Burmeister, Co. incompleta Banks, Co. reaction mixture was warmed to −30°C over 1 h, maintained quadripunctata Burmeister (USA), and Co. septempunc- at this temperature for 3 h, then quenched with 5 ml of a 25% tata Wesmael (China); Chrysoperla (= Cl.) rufilabris ammonium acetate solution. The mixture was extracted with (Burmeister) (USA) and Cl. sp. (Brazil); Plesiochrysa hexane (3×15 ml), and the combined extracts were washed ramburi (Schneider) and Mallada spp. (Australia). with water (2×10 ml) and brine (10 ml), and then dried. All J Chem Ecol (2009) 35:1181–1187 1183 Table 1 Chrysopids used for analyses of prothoracic gland secretions Speciesa Sex No. Dateb Location Collection/Sampling Method Chrysopa oculata M 5 5 July Beltsville, MD Iridodial trap/Gland dissection M 4 27 Sept. Beltsville, MD Iridodial trap/Gland dissection Chrysopa nigricornis M 2 12 June Spokane, WA Iridodial lure/Gland dissection M 10 7 August Spokane, WA Fluorescent lightc/Gland dissection Chrysopa incompleta M 8 24 Sept. Byron,