Semiochemistry of the Goldeneyed Lacewing Chrysopa oculata: Attraction of Males to a Male-Produced Pheromone

Abstract

Gas chromatographic-electroantennographic detection (G3C-EAD) experiments showed that antennae of males and females of the goldeneyed lacewing, Chrysopa oculata Say (Co. = Chrysopa), consistently responded to four compounds extracted from the abdominal cuticle of males:nonanal, nonanol, nonanoic acid, and (1R*,2S*,5R*,8R*)-iridodial. These compounds were not detected from abdominal cuticle of females. Thoracic extracts of both sexes contained antennal-stimulatory 1-tridecene and EAD-inactive skatole. Chrysopa oculata adults were most sensitive to (1R,2S,5R,8R)-iridodial standard at an EAD-response threshold between 0.1 and 1 pg, which was 10-100 times lower than thresholds for nonanal and nonanoic acid, and up to 10,000 times lower than thresholds for other compounds tested. A similar EAD response pattern was also found in another Chrysopa sp. (Co. quadripunctata Burmeister). In field-trapping experiments, (1R,2S,5R,8R)-iridodial was the only male-specific compound that attracted Co. oculata males. Males also were weakly attracted to (1R,4aS,7S,7aR)-nepetalactol (an aphid sex pheromone component), probably due to the 5% (1R,2S,5R,8R)-iridodial present in the synthetic sample as an impurity. A herbivore-induced plant volatile, methyl salicylate, increased attraction of males to (1R,2S,5R,8R)-iridodial, whereas 1-tridecene was antagonistic. No females were caught in the entire study. Scanning electron micrographs revealed numerous male-specific, elliptical epidermal glands on the 3rd-8th abdominal sternites of Co. oculata, which are likely the pheromone glands. Another lacewing species, Chrysoperla rufilabris (Burmeister) (Cl. = Chrysoperla), did not produce male-specific volatiles or possess the type of gland presumed to produce pheromone in Co. oculata males, but (Z)-4-tridecene was identified as a major antennal-stimulatory compound from thoracic extracts of both sexes of Cl. rufilabris. Thus, (1R,2S,5R,8R)-iridodial (or its enantiomer) is now identified as a male-produced male aggregation pheromone for Co. oculata, the first pheromone identified for lacewings.

Prothoracic Gland Semiochemicals of Green Lacewings

“…is skatole (3-methylindole) (Blum et al 1973;Güsten and Dettner 1991), and extended the known distribution of this foul-smelling PG compound to two additional genera of green lacewings, Plesiochrysa and Ceraeochrysa. However, earlier reports of 1-tridecene in the prothoracic gland secretions of Chrysopa oculata (Blum et al 1973;Zhang et al 2004) and Co. nigrispinus (Zhang et al 2006a) are here shown to be in error. Synthetic 1-tridecene did not coelute with the tridecene found in the PG secretions of these Chrysopa spp., whereas synthetic (Z)-4-tridecene did coelute with the natural products.…”

“…Green lacewing adults have long been known to communicate intraspecifically via substrate vibrations (e.g., Henry 1982), but only recently was it discovered that males in the genus Chrysopa produce aggregation pheromones from thousands of elliptically shaped glands embedded in their abdominal cuticle Zhang et al 2004Zhang et al , 2006a. Interestingly, female goldeneyed lacewings [Neuroptera: Chrysopidae: Chrysopa (= Co.) oculata Say] do not enter traps baited with pheromone (1R,2S,5R,8R-iridodial) Zhang et al 2004), presumably because females attract males via substrateborne vibrations at close range (Henry 1982).…”

“…Interestingly, female goldeneyed lacewings [Neuroptera: Chrysopidae: Chrysopa (= Co.) oculata Say] do not enter traps baited with pheromone (1R,2S,5R,8R-iridodial) Zhang et al 2004), presumably because females attract males via substrateborne vibrations at close range (Henry 1982). However, Chauhan et al (2007) showed that significant numbers of wild Co. oculata females are attracted to the vicinity of iridodial dispensers in the field, and observed that the attracted females laid eggs on soybean leaves near the dispensers.…”

Structure, function and context : the impact of morphometry and ecology on olfactory sensitivity

“…The highly specific relationships of insect predators, herbivores, parasites and pollinators provide simple, readily testable models for olfactory specialization, and both behavioral methods and electro-anetennogram detection have shown that thresholds are lowered for ecologically relevant compounds. This kind of specificity is well known for conspecific pheromone components (Cabrera et al, 2001, Jintong et al, 2001, Kalinova et al, 2003, Yamamoto et al, 1999, Zhang et al, 2004, and others) Other important compounds identifying preferred prey, forage plants, oviposition sites and other important resources are also detected with higher sensitivity (Backman et al, 2000, Bichao et al, 2001, Costantini et al, 2001, Rostelian et al, 2000. Antennal detection is highly selective, discriminating very slight changes in odorant compound structure (carbon chain length, functional group, stereochemistry) that in turn reflect prey or host specificity that is in some cases very narrow, famously in the case of the human-specializing malaria vector Anopheles gambiae (Costantini et al, 2001).…”

Detection of oviposition-deterring larval tracks in Chrysopa oculata and Chrysopa perla (Neuroptera: Chrysopidae)

“…In gas chromatographic-electroantennographic detection (GC-EAD) experiments, males and females of C. oculata reacted to four compounds from the abdominal cuticle of males that are absent in females Zhang et al, 2004). Both males and females were strongly attracted to iridodial, a malespecific compound of C. oculata, and aggregated near lures of this compound in nature, suggesting the possibility it could be used to increase oviposition in targeted fields (Chauhan et al, 2007).…”