Citronellic acid

Alkaline bleach treatment of mixed-stage animals yielded a sterile egg suspension, which was rocked overnight in 3 mL M9 solution to yield synchronized, starved L1 larvae⁵⁵ . Approximately 100,000 synchronized L1 larvae were added to 125 mL Erlenmeyer flasks containing 10 mL M9 media and 300 μM citronellic acid (Sigma-Aldrich 303429), phytanic acid (Sigma-Aldrich P4060), retinoic acid (Sigma-Aldrich R2625), geranic acid (Aldrich 427764), or an equivalent volume of methanol only (vehicle control) and were incubated at 20 °C with shaking at 180 RPM for 24 h. Cultures were transferred to 15 mL conical tubes and centrifuged (500×g, 22 °C, 1 min), and the resulting supernatant (exo-metabolome) was transferred to a fresh conical tube and snap frozen. Remaining L1 pellet was washed three times with M9 before snap freezing in liquid nitrogen.

High purity essential oil components carvacrol, geraniol, eugenol, methyl eugenol, trans-cinnamaldehyde, citronellic acid, (±)-citronellal, α-pinene, linalool, R (+)-limonene, eucalyptol, (−)-terpinen-4-ol, and menthone were obtained from Sigma-Aldrich (St. Louis, MO), whereas thymol and (±)-camphor were obtained from Alfa Aesar (Hill, MA) (Table S1). These active constituents are found in various aromatic plants (Table S1). All fifteen essential oil components (Table S1) were selected based upon the previous toxicity literature on different urban and agricultural pests^{22 (link)–31 (link)}. The positive controls dichlorvos (≤100% purity) and bifenthrin (98% purity) were obtained from Sigma Aldrich and Chem Service Inc. (West Chester, PA), respectively. Analytical grade solvents such as acetone, ethanol and dimethyl sulfoxide (DMSO) were purchased from Fisher Scientific (Pittsburgh, PA). Buffer salts and other reagents used for preparation of HEPES (4-(2-hydroxyethyl)−1-piperazineethanesulfonic acid)-buffered physiological saline were purchased from Sigma-Aldrich, Fisher Scientific and Avantor Performance Materials, LLC (Center Valley, PA).

1,8-Cineole, citronellal, citronellic acid, citronellol, linalool, (R)-limonene, (R)-α-pinene, (S)-β-pinene, (R)-pulegone, α-terpinene, γ-terpinene, thymol and PBO used in the bioassays or as chromatographic standards were purchased from Sigma-Aldrich (St. Louis, MO, United States). HPLC grade acetone was purchased from Merck (Darmstadt, Germany).