Concentration mean values (scatter) of root VOCs consistently released by oak roots.

<p>As measured in 10 cm distance to feeding-damaged oak roots in original soil.</p><p>As measured to be released by washed oak roots (undamaged, mechanically damaged, feeding-damaged).</p><p>As lowest concentration stimulating the white grub antenna.</p><p>As measured in the center of the choice-test arena within the first hour of experiment.</p>1<p>Purity checked by gas chromatography-mass spectrometry, deviations from label given in brackets.</p>2<p>Compounds released by <i>Quercus</i> spec. roots under special circumstances.</p>a<p>passive sampling by SPME (n = 3).</p>b<p>active sampling by TDS (n = 5).</p>c<p>active sampling by CLSA (n = 9).</p>d<p>calculated from vapour pressure based on Yaws CL (2007) The Yaws Handbook of Vapor Pressure. Houston: Gulf Publishing Company and based on SciFinder® database <a href="https://scifinder.cas.org" target="_blank">https://scifinder.cas.org</a>.</p><p>°Racemic Mixture;</p><p>n.d. not detected</p><p>Different letters indicate significant differences,</p>*<p>:P<0.05,</p>**<p>:P<0.01,</p>***<p>:P<0.001.</p

Dose-response curves of <i>M. hippocastani</i> to different odors.

<p>The selected test odors are released by oak-roots damaged by feeding larvae. Dose- response curves to anisol (N = 8), eucalyptol (N = 3), octan-3-one (N = 6), (1R)-camphor (N = 8), and furanoid trans-linalooloxide (N = 3); mean values of antennal responses (amplification factor 100). Lowest dilutions eliciting responses significantly different to baseline noise from at least 50% of all antennae are marked as full symbols.</p

GC-MS/EAD chromatograms of CLSA-samples from oak roots.

<p>A) undamaged oak roots The upper trace shows the electroantennographic response of a larval antenna (EAD), the lower trace shows the total ion current of the mass spectrometer (MSD). Compounds detected consistently (numbers as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045827#pone-0045827-t001" target="_blank">Table 1</a>): 4∶6-methyl-5-hepten-2-one, 7: furanoid trans-linalooloxide, 8: nonanal, 9/10: (R/S) camphor, 11: borneol, 12: decanal. Not consistently detected compounds are labeled by o. B) feeding damaged oak roots The upper trace shows the electroantennographic response of a larval antenna (EAD), the lower trace shows the total ion current of the mass spectrometer (MSD). Compounds detected consistently (numbers as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045827#pone-0045827-t001" target="_blank">Table 1</a>): 1: anisol, 3: octan-3-one, 5∶2-ethyl-hexan-1-ol, 6: eucalyptol, 7: furanoid trans-linalooloxide, 8: nonanal, 9/10: (R/S) camphor, 11: borneol. Not consistently detected compounds are labeled by o.</p

SEM pictures of <i>M. hippocastani</i> apical and subapical antennomere.

<p>A) Lateral view of the apical and sub-apical antennomere. B–D) Dorsal, apical, and ventral view of the apical antennomere, respectively. In B and D the multiporous olfactory sensilla (MOS) can easily be observed. In C the apical part of the antennomere is shown, with the dorsal (left) and ventral (right) MOS. E) MOS on the inner surface of the lateral protrusion of the subapical segment. F) Close up view of the MOS surface, pierced by numerous tiny cuticular pores. Bar scale: A, B, D: 200 µm; C:100 µm; E: 50 µm; F: 2 µm.</p

<i>M. hippocastani</i> apical antennomere.

<p>A) Light microscopy cross section showing the dorsal (DMOS) and ventral MOS (VMOS). B) TEM cross section at the level of the dorsal MOS, showing two bundles of outer dendritic segments (ODS). C, D, F) Details of the dendritic branches (DB) filling the space below the porous cuticle (PC), pore tubules (PT) can also be observed. E) Two bundles of four dendrites taken at the level of the ODS. Bar scale: A: 50 µm; B: 10 µm; C, E: 2 µm; D: 500 nm; F: 200 nm.</p

<i>M. hippocastani</i> brain including the antennal lobes (AL), frontal views.

<p>A) Maximum projection of 229 serial confocal images: Green codes for anti synapsin immunostaining, magenta for a dye (dextran) backfill from the antenna. B) 3D-reconstruction of A showing the brain outline (light gray) and selected brain areas: yellow, reconstructed from the antenna backfill; the other brain areas, including the contralateral AL (blue), the mushroom bodies (red), the central complex (darker green), the protocerebral bridge (lighter green), and remaining neuropil (gray) are reconstructed from the anti synapsin immunostaining which can be used to label neuropil areas in insects (see e.g. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045827#pone.0045827-Nordenhem1" target="_blank">[10]</a>). Arrowheads, projection to the subesophageal ganglion; arrows, cell bodies of two antennal motoneurons; star, projections to the lateral protocerebrum; AN, antennal nerve. C) Single confocal images of the image stack of the left antennal lobe in A, clearly showing many spheroidal structures, the so called olfactory glomeruli in the larval beetle brain. AL - labeled by the synapsin antibody (C1) and the backfill staining (C3). C2: Overlay of C1 and C3.</p