Photos of the real and the artificial larvae.

<p>A) A fifth instar <i>Epirrita autumnata</i> larva on a branch. B) Larval feeding damage on mountain birch (<i>Betula pubescens</i> ssp. <i>czerepanovii</i>) leaves. C) A plasticine larva on a mountain birch branch. D). A beak marking on a plasticine larva indicating a predation attempt by an insectivorous bird.</p

Spearman's rank correlation coefficients (<i>r</i>_S) between individual volatile organic compound emissions in the first measurement (6 days after the start of defoliation) and the total sum of damaged plasticine larvae per tree (<i>n</i> = 28 trees) in both herbivore and control trees.

<p>Column ‘No.’ refers to the number of the compound in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002832#pone-0002832-g002" target="_blank">Figure 2</a>. Column ‘Group’ indicates into which group of VOCs the compound belongs. (^*: <i>p</i><0.05; ^**: <i>p</i><0.01).</p

Scatter plots of three volatile organic compounds (VOCs) and the total sum of damaged plasticine larvae in herbivore (black dots) and control (grey dots) trees (<i>n</i> = 28). A) (<i>E</i>)-DMNT, B) linalool and C) β-ocimene.

<p>Note the different x-axes in the panels.</p

The volatile organic compound (VOC) emissions from herbivore (black bars) and control (grey bars) birch branches (ls means+SE from statistical models are shown).

<p>A) six days, <i>n</i> = 14 in both control and herbivore trees, and B) 10–11 days since the start of defoliation by autumnal moth larvae, control: <i>n</i> = 7 and herbivore: <i>n</i> = 6. Compounds: (1) α-pinene, (2) β-myrcene, (3) limonene, (4) β-ocimene, (5) linalool, (6) (<i>E</i>)-DMNT, (7) α-copaene, (8) α-humulene, (9) caryophyllene oxide, (10) (<i>E</i>)-β-caryophyllene, (11) β-bourbonene, (12) cis-3-hexenyl acetate, (13) cis-3-hexen-1-ol+(<i>E</i>)-2-hexenal, (14) nonanal, (15) cis-3-hexenyl butyrate. (*: <i>p</i><0.05; **: <i>p</i><0.01; ***: <i>p</i><0.001).</p

The daily numbers of damaged plasticine larvae found from herbivore (black bars) and control (grey bars) birches.

<p>The X-axis shows the number of days since the start of defoliation by autumnal moth larvae in the herbivore trees. Solid and hatched arrows show the days when the volatile organic compounds (VOCs) and net photosynthesis rate, respectively, were measured.</p