Pheromone extraction procedure

Chemical investigations have surpassed studies which use chemicals or glandular extracts in behavioral studies. Field testing of compounds is slow and difficult. Although it is relatively easy to trap Southern pine beetles with pheromone, similar procedures employing standard compounds found in the exocrine extracts of bees have not been successful. The identiflcation of compounds has little value unless their significance to the biology of the bees can be determined with quantitative behavioral assays. 

Fig. 4 Gas chromatographic traces of extracts from females of the pale brown chafer Phyl-lopertha diversa monitored by a conventional detector, flame-ionization detector (FID), and a biosensor, electroantennographic detector (EAD), using a male antenna as the sensing element. Although the peak of the sex pheromone (arrow) is hardly seen in the FID trace, its pheromonal activity was initially indicated by the strong EAD peak. Structural elucidation, followed by synthesis and behavioral studies lead to the identification of an unusual sex pheromone, l,3-dimethyl-2,4-(lff,3ff)-quinazolinedione [124]. It is unlikely that this minor compound would be fished out by a bioassay-oriented isolation procedure...

To exclude the possibility of response toward tactile cues delivered from silk, silk has been extracted with various solvents and then retested in behavioral experiments (marked W in Table 4.1). This procedure implies pheromone usage but is not conclusive. The experimentum crucis, abehavioral test of the extract for pheromonal activity, often was not performed, particularly in older studies. A complicated issue is that solvent extraction of silk can alter its physical characteristics, as shown in... 

The behavior of the males was used in a bioassay-guided identification of the pheromone, which was extractable by polar solvents such as water or methanol. The bioassay apparatus consisted of a cardboard channel with silk samples treated with different extracts. A positive response consisted of a male producing a typical drumming behavior upon contact with a stimulus. Because males responded to some extent to silk without pheromone, individual spiders were tested first with inactive silk, followed by extract-treated silk (Tichy et al, 2001). GC-MS analyses of the active silk extracts were not successful, even using several derivatization procedures. However, the pheromone structure was deduced by NMR spectroscopy... 

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