Bug pheromones

In the sections that follow, the various bug families are dealt with in their commonly accepted taxonomic order [3]. It should be noted that pheromones have been described from less than half of the bug families. Even for those families in which pheromones are known, pheromone identifications have been carried out for only a few species, leaving a vast number of semiochemicals still to be discovered. 

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More recently, solid phase microextraction (SPME) [22] has been applied to the analysis of bug pheromones, using two techniques. In the first, headspace volatiles are trapped on the SPME fiber, analogous to trapping on SuperQ [e.g., 23]. Alternatively, if the source of the pheromone is known, the SPME fiber can be wiped on the cuticle to directly adsorb the compounds [24]. In either case, the fiber is then thermally desorbed directly into a GC or GC-MS. Whereas this method is excellent for analysis, with good recoveries, it does not provide a sample that can be used for bioassays or for isolation of an active compound. 

Electroantennogram studies have also proven fruitless in the search for Lygus bug pheromones. Antennae from males and females respond to numerous compounds in extracts from both sexes, and although some sex-specific differences have been noted in the magnitudes of antennal responses, no obvious pheromone candidates have emerged [147,148]. Even with abundant evidence that females use a volatile sex attractant, Lygus spp. pheromones have resisted all attempts at identification for more than 30 years. 

I explained this category in the case of the German cockroach pheromone (104), and also discussed the spined citrus bug pheromone [(3/ ,4S)-74], whose opposite enantiomer was as active as the pheromone itself. Females of the maritime pine scale Matsucoccusfeytaudi) use (3.S ,7R)-118 as the sex pheromone. Its OR,1R )-isomcr also showed bioactivity similar to the natural pheromone, while M. feytaudi males responded very weakly to the two other stereoisomers. It therefore seems that only the stereochemistry at C-7 of 118 is important for the expression of pheromone activity.139... 

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