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Figure 1. 

Phytohormone (auxins and cytokinins) and defense-related jasmonate and salicylate levels in insect frass. (a) Auxins in superworm (SW) and mealworm (MW) frass under five diet treatments: Bran (control), PE + bran (polyethylene + bran), PE + bran + Suc (polyethylene + bran + sucrose), PS + bran (polystyrene + bran), and PS + bran + Suc (polystyrene + bran + sucrose). From left to right: Indole-3-acetic acid (IAA), IAA–L-leucine (IAA-L-LEU), indole-3-lactic acid (I3LA), 3-indoleacrylic acid (IA), IAA–L-phenylalanine (IAA-L-PHE), IAA–L-valine (IAA-L-VAL), and 3-indoleacetonitrile (3IAN). Frass from plastic-fed superworms had higher IAA compounds than bran-fed controls (note the prominent peaks in the blue bars for the PE and PS diets), whereas mealworm frass auxin levels remained similar. Sucrose added to the plastic diet (striped bars) attenuated the auxin levels in superworms. (b) Cytokinins in the same frass samples: Trans-zeatin (tZ), ortho-topolin (oT), and trans-zeatin riboside (tZR). Cytokinins are lower than auxins (note the y-axis in ng/g). Superworm frass had more cytokinins than mealworm frass, especially under the PE diet (green bars), but differences among diets were minor. All cytokinin levels were in the ng/g range or below. (c) Jasmonate levels in superworm (left) and mealworm (right) frass across diets. Jasmonic acid (JA) and jasmonoyl-L-isoleucine (JA-Ile) are shown. Plastic-fed mealworm frass (especially the PS + Suc treatment, dark pink striped bar) had elevated JA (~2 to 3 µg/g) compared with bran-fed mealworms (~0.5 µg/g). Superworm frass showed a smaller increase in JA under plastic diets (~1 µg/g at most). JA-Ile exhibited parallel trends at lower concentrations (tens of ng/g). Sucrose addition in mealworm diets enhanced JA and JA-Ile accumulation (compare solid vs. striped pink bars), whereas in superworms, sucrose had a minimal effect. (d) Salicylate levels in frass: Salicylic acid (SA) and its glucose conjugate, salicylic acid 2-O-β-glucoside (SAG). Superworm frass contained higher SA than mealworm frass under all diets. Plastic feeding increased SA levels in superworms (peaking at around 5 µg/g under the PS diet, brown bar) relative to bran controls (~1.5 µg/g), whereas mealworm SA increased modestly (~2 to 3 µg/g). SAG was present at much lower levels (≤ 0.05 µg/g). For the full panel of phytohormones and chemicals tested, see the Supplementary Table S5. Note that the data in the Supplementary Table S5 are shown in nmol/g, but we used µg/g here for better comparisons. Data shown here are averaged from the replicates. All values represent the mean ± standard deviation (SD) of biological replicates; the significance of differences relative to the bran controls is indicated by * = p < 0.05, ** = p < 0.01, and *** = p < 0.001.