δD of organic matter and extracted water of plant and insect tissues are linearly correlated to δD of irrigation water.

<p>(a) The δD values of the organic matter of plants (solid triangles, dotted line), caterpillars (plus ‘+’ signs, barred-dotted line), and moths (open circles, barred line) increased linearly with the δD value of irrigation water (y_plant = 0.59x−107.5, r² = 0.74; y_caterpillar = 0.59x−81.2, r² = 0.90; y_moth = 0.59x−67.8, r² = 0.90). These relationships had a common slope that was significantly less than 1. Note that the δD value of soil (open squares) did not differ from that of irrigation water (y = x, solid line). Plant, caterpillar, and moth tissues are significantly depleted in deuterium relative to irrigation water. (b) The δD value of water extracted from plants (solid triangles, dotted line), caterpillars (plus ‘+’ signs, barred-dotted line), and moths (open circles, barred line) was also linearly related to that of irrigation water (y_{plants H2O} = 0.73x+34.7, r² = 0.86; y_{caterpillar H2O} = 0.85x+46.8, r² = 0.94; y_{moth H2O} = 0.41x−19.2, r² = 0.44). Extracted water samples from plants, caterpillars and moths were enriched in deuterium relative to irrigation water. The slope of the relationships of the δD value of irrigation water to water extracted from plants and caterpillars did not differ significantly. The slope of the relationship between the δD value of irrigation and that of water extracted from moths was significantly shallower.