Repellents, identification

In Alloxysta victrix, 6-methylhept-5-en-2-one 16, which is produced by both males and females, was identified as potentially attractive to the males and slightly repellent to the females in Y-tube olfactometer assays [60]. In this study, the activity was also dependent on prior exposure of the insects to the compound. Naive insects responded more strongly than previously exposed ones. This underscores a second difficulty in the bioassay-guided identification of parasitoid hymenopteran pheromones the responses are very dependent on the context and on prior exposure. Learning has been demonstrated in several species of parasitic hymenoptera [61-65]. 

Although many queen-produced pheromones are actively being studied in ants, particularly in the fire ant (Solenopsis invicta) [10,105-110], chemical identifications remain elusive. However, there have been a few recent advances in ants. The queen of the slave-making species Polyergus rufescens produces de-cyl butanoate 60 that repels host workers when upsurping a colony [111]. Males of Formica lugubris are attracted to alate queens by undecane 61, tridecane 62 and (4Z)-tridec-4-ene 63 [112]. 

Tiedman, G. T., Oh, J. H., Oita, K., and Christoffers, G. W. (1976). Wildlife damage control II partial identification of the active ingredients in big game repellents derived from... 

An ISI is used with less polar effluents and is the workhorse for standard HPLC systems since it can take flow rates up to 2mL/min. It is most commonly used to produce intact molecular ions for molecular weight determinations, but it can be set up with an ion repeller to cause fragmentation that can provide preliminary compound identification and structural information. 

S. Auriola, T. Naaranlahti, R. Kostiainen, S.P. Lapinjoki, Identification of indole alkaloids of Catharanthus roseus with LC-MS using CID with the TSP ion repeller, Biomed. Environ. Mass Spectrom., 19 (1990) 400. 

The two examples discussed show the bioanalytical applicability of LC/MS, both in qualitative analysis and in target compound analysis. Although the moving belt interface owing to its El capabilities is ideally suited for the identification of unknown compounds and is used often for that purpose, identification problems can sometimes also be solved with thermospray LC/MS, for instance by applying repeller-induced fragmentation, and LC/MS/MS. The PSS approach is an example that indicates that LC/MS still can be improved. A more elaborate discussion on the so-called multidimensional approaches in LC/MS is given elsewhere (14). 

To illustrate the approach to the identification of unknown materials by using infrared spectroscopy, we will work through an example. Citronellal is the terpenoid responsible for the characteristic aroma of lemon oil, and is used in perfumes and also as a mosquito repellent. The infrared spectrum of citronellal is shown in Figure 4.5a. We can use this spectrum to determine the molecular structure of this compound. 

Many of the contributions in this book are concerned with pheromones, i.e., chemical stimuli that are employed by crustaceans to attract conspecifics. However, chemical communication also includes substances that are used to repel other organisms. These repellents could be especially useful in the aquaculture context, e.g., to repel parasites or fouling organisms. Many crustaceans are parasites of commercially important fish species (e.g., salmon) and both traps and repellents could be used in controlling infection levels (e.g., Mordue and Birkett 2009). Similarly, barnacles are abundant fouling organisms in suspended structures or seawater systems and developing techniques to suppress their recruitment is one of the main motivations behind the identification of settlement factors (Clare, Chap. 22). 

The first section. Bioregulation of Insect Behavior and Development, includes chapters on arthropod and insect repellents, the identification of a beetle pheromone, nonparalyzing factors fi om hymenoptera, endogenous regulation of pheromone biosynthesis and mating, and systems for controlled release of pheromones. 

Honey bee queens produce a rectal secretion which repels aggressive workers in the colony as an example of an intraspecific repellent (1 6). If such pheromonal repellents are commonly produced by social insects, a cornucopia of deterrent natural products awaits identification in the exocrine secretions of these arthropods. 

Wimalaratne, R Slessor, K Borden, J. Chong, L. and Abate, T. (1996). Isolation and identification of house fly, Musca domestica L., repellents from pepper tree, Schinus molle L. /. Chem. EcoL, 22,49-59. 

Utilizing the continuous mass spectrometric techniques developed by Arnot and co-workers and Hornbeck and Molnar in which reaction identification is made from considerations of the appearance potentials of the product ions and from the effects of electron energy, pressure, and repeller potential on product-ion intensity, homonuclear associative ionization reactions have been reported in helium, " in neon, "- " " i46A9,5o,52-si,62) krypton,< " " - " > in... 

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