Identification and Bioassays of Sex-Specific Compounds From a Nuisance Net-Spinning Caddisfly Smicridea fasciatella (Trichoptera: Hydropsychidae).

Municipalities in Arizona and Nevada along the Colorado River are subject to seasonal mass emergences of a nuisance net-spinning caddisfly, Smicridea fasciatella McLachlan (Trichoptera: Hydropsychidae). Here, we describe the characterization and field testing of S. fasciatella extracts to evaluate their potential as lures in baited traps. Solvent extracts of external (i.e., full body-cuticular hydrocarbon, abdominal hexane washes) and internal (i.e., crushed abdomen) parts of adult S. fasciatella were prepared from both sexes, and analyzed by coupled gas chromatography-mass spectrometry (GCMS). Several sex-specific compounds were identified, including (6Z,9Z)-6,9-nonadecadiene and (3Z,6Z,9Z)-3,6,9-nonadecatriene from males, and 2-undecanone, 2-tridecanone, and a heptadecene isomer from females. Extracts from both sexes were also analyzed by coupled gas chromatography-electroantennographic detection (EAD) using antennae of males for detection. Antennae of males weakly responded to 2-undecanone and 2-tridecanone, and to their corresponding alcohols, 2-undecanol and 2-tridecanol, which were included in field tests. Extracts of adult males did not elicit a response from male antennae, suggesting that males do not produce aggregation pheromones attractive to other males. The synchronized, dense populations of lekking males and other possible mating signals (e.g., visual recognition) may have contributed to the minimal attraction seen to test lures deployed in PHEROCON 1C traps. Overall, our results suggest that for this species, attractant pheromones have minimal or no role in bringing the sexes together for mating.
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