## 4 Materials and Methods
### Quantification of Volatile Compounds  
Terpenoid compounds present in the gut of _D. rhizplugus_ males and females were sampled and quantified in: (1) unfed pre-emerged insect; (2) solitary fed males and (3) solitary fed females; (4) fed males paired with females; and (5) fed females paired with males. The unfed pre-emerged insects were immediately processed for analysis by gas chromatography--mass spectrometry (GC-MS). The insects used in the other treatments (2-5) were confined during 18 and 24 h into uninfested _Pinus leiophylla_ fresh logs. These times were selected because a preliminary analysis demonstrated that in this period, in laboratory conditions, the production of volatiles by insects is better than in shorter times (<15 h). In addition, to follow up the production of volatiles, these were also recorded and quantified at 43 h. For insects in pairs, females were first introduced alone into the bark during 4 h, and afterwards, a male was introduced with each female and both stayed inside for another 18, 24, and 43 h. Twelve replicates were collected for each treatment and feeding time. All insects were set individually into 0.25 mL glass inserts (SUPELCO, Sigma-Aldrich Corp., Milwaukee, WI, USA) containing \(\sim\)0.3 mg of the adsorbent Porapak Q, during 24 h in dark conditions at room temperature in a stream of purified air, in order to collect the volatiles released by them [40; 108]. Later, each insect was removed from its vial and dissected to obtain the gut. Volatiles were extracted from the Porapak Q and from the gut tissue with 100 mL of hexane spiked with 3.8 ng/mL of cycloheptanone (99 purity, Sigma-Aldrich Corp.) as an internal quantitative standard. The tissue was gently macerated against the glass insert wall and reserved for 15 min for passive extraction at room temperature. Later, the total extract was transferred into a clean glass insert and kept at \(-20\)\({}^{\circ}\)C. Negative control extracts were also collected from glass inserts in which no beetles were introduced.  
One microliter of each extract was analyzed by GC-MS (7820A GC System-5975 Series MSD Agilent Technologies, Santa Clara, CA, USA) in splitless mode with a (5%-Phenyl)-methylpolysiloxane column (Agilent J&W HP-5 ms 30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m). The temperature program of the GC oven was 50 \({}^{\circ}\)C for 1 min, 2 \({}^{\circ}\)C/min to 100 \({}^{\circ}\)C, then 16 \({}^{\circ}\)C/min to 200 \({}^{\circ}\)C. The quantification of each compound was made by internal standardization method and converted to nanograms based on the relative responses obtained from serial dilutions of synthetic standards [fenchyl alcohol (96% purity, Sigma-Aldrich Corp., Milwaukee, WI, USA), myrtrenal (98% purity, Sigma-Aldrich Corp.), myrtenol (95% purity, Sigma-Aldrich Corp.), cis-verbenol (95% purity, Sigma-Aldrich Corp.), trans-verbenol (95% purity, PheroTech, Delta, BC, Canada), and verbenone (99% purity, Sigma-Aldrich Corp.). The identification of each compound from the extracts was accomplished by matching the retention times of synthetic standards and mass spectra searches with the NIST Mass Spectral Search Program (version 2.2) for the NIST/NIH/EPA Mass Spectral Library.