Pheromone deterrents

Additional compounds found in the pheromone gland of female cigarette beetles are (2S,3R,l R)-2,3-dihyro-2-ethyl-3,5-dimethyl-6-(r-methyl-2 -oxo-butyl)-4ff-pyran-4-one 121 (P-serricorone), its (rs)-epimer (a-serricorone), and its reduction product, serricorole, 122 which shows (l/S,2/S)-configuration [245-247]. These compounds showed only weak attractivity [245], however, they obviously act as oviposition deterrents [248,249]. 

When disturbed or molested, these insects release small droplets of hemo-lymph from the tibio-femoral joints of their legs, and it is now well established that the deterrency exhibited by many species of coccinellids towards potential predators results from the presence of repellent and bitter alkaloids in that fluid [ 12,13]. In ladybirds, this unpalatability is associated with a bright aposematic coloration and a characteristic smell due to 3-alkyl-2-methoxypyrazines [14, 15]. The beetles use these molecules not only to reinforce the visual alerting signal on an olfactory level, but also as aggregation pheromones [16]. 

Only a few compounds or mixtures of compounds have been shown beyond doubt to be mammalian pheromones. This is the main reason why the subject matter of this chapter is not restricted to pheromones and why exocrine secretions and other mammalian excretions in general will be discussed as possible sources of pheromones, even though their role in the chemical communication of the species under discussion has not yet been established. Feeding deterrents are not discussed. In general defensive secretions are also not discussed, but the anal sac secretions of the mustelids are included, because it is possible that these secretions could also fulfill a semiochemical role, in addition to being used for defense. 

Key words alkaloids, attraction, case smdy, deterrence, ecology, food, MEC, micro-evolution, pheromones, quinolizidine alkaloids, selective toxicity, sexual life... 

Alkaloids are generally bitter, which suggests that these compounds could be utilized as either animal deterrents or in intra- or interspecific competition of plant species. In some cases repellent alkaloids (e.g., pyrrolizidine alkaloids) are sequestered by herbivores and converted to compounds that function as sex pheromones while still possessing deterrent activities. The insect derivation of sex pheromones from known repellent alkaloids that accompany the ingested nutrients... 

The presence of pyrrolizidine alkaloids in arctiid moths that had been reared on Senecio and Crotalaria species has been established by Rothschild et al.4S These alkaloids are stored in the moths, and serve as a deterrent to vertebrate predators and as precursors for insect sex pheromones. A pyrrolizidine alkaloid metabolite from the Cinnabar moth (Tyria jacobaea L.), named callimorphine, has been shown to have the structure (49) on the basis of mass-spectral and degradative evidence.46 The structure (49) was confirmed by synthesis of callimorphine and a diastereo-isomer by treatment of 9-chlororetronecine with the sodium salt of ( )-2-acetoxy-2-methylbutanoic acid. 

Alarm pheromone defensive agent Formica, ants) [toxic] Feeding deterrents (through generation of reactive isothiocyanates, R=N=C=S)... 

There has been considerable progress in isolating and identifying compounds that affect Insect behaviour. A recent review contains more than 800 references to the literature and lists over 300 compounds as insect attractants, attractant pheromones and related compounds together with the corresponding insect species (26). Other pheromones (trail pheromones, hair pencil secretions, etc.), feeding deterrents, ovipositlon deterrents, an other types of behavioural compounds are not included in this comprehensive review, but the volume of Information on behavioural compounds is constantly being expanded as new compounds are identified. 

Monarch butterflies t.g., Danaus plexipus) combine two sets of natural compounds. Larvae feed on plants rich in cardiac glycosides and use them as chemical defense compounds. Adult butterflies visit plants with PAs, where they collect PAs that are converted to pheromones or transferred to their eggs 4,17,31,33,361,515). A similar PA utilization scheme was observed with larvae of the moth Utetheisa ornatrix 367,516), where the compounds were shown to be deterrent for spiders and birds 225, 525). The chrysomelid beetle Oreina feeds on PA-containing plants, such as Adenostyles, and stores the dieUuy PAs in the defense fluid 463,524). 

Although much is known about the crustacean endocrine system, there remains a paucity of information concerning the use of hormones as other chemical messengers, such as pheromones or allelochemicals. Most of the work in this area (pleiotropic effects of crustacean hormones) has focused on the molting hormones (ecdysteroids). Due to the lack of species-specificity, it is unlikely that ecdysteroids are sex recognition pheromones. Strong evidence has been published, however, that ecdysteroids act as feeding deterrents, both within and between species. Ecdysteroids also appear to be... 

Similar to reports from fishes, the crustacean molting hormone 20-hydroxyecdysone (also known as crustecdy sone) had also been proposed to function as a sex pheromone in several decapod species (Kittredge et al. 1971). However, later studies have shown that crustecdysone does not play a role as sex pheromone in crab species such as Callinectes sapidus and C. maenas (Gleeson et al. 1984 Hardege et al. 2002) but rather appears to function as feeding deterrent (Chang, Chap. 21). 

Chemical ecology The amines are components of the plants chemical defence systems. They have antifee-dant or deterrent effects on many animds. Adapted insects of various taxa (Lepidoptera, grasshoppers, beetles, and greenflies) are able to store and utilize the plant P. a. They use them as protective substances against insect-eating predators and display their inedibility through conspicuous warning colors (aposema-tis). Some Lepidoptera also use plant P. a. as precursors for their pheromones. ... 

The use of single semiochemicals in the field is not usually sufficient for pest control, but by combining semi-ocheinicals, substantial protection can be achieved using an integrated approach called the push-pull system. The push is located in the crop and may comprise antifeedants, nonhost semiochemicals, attraction of predators or parasitoids, oviposition deterrents, or epideictic pheromones. The pull component comprises lures or trap areas away from the crop containing the sex pheromone, host odors, oviposition... 

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. 

In the present report, we present results of very recent investigations on the chemistry and deterrent activities to ants of the diverse compotinds identified as exocrine compounds of thrips. In addition, we evaluate the repellency of some honey bee natural products to honey bee workers as an example of how pheromones themselves can be candidates as deterrents... 

Young honey bee queens produce a repellent pheromone that effectively tranquilizes workers that may interact antagonistically with these virgin females (16). The active compoimd, o-aminoacetophenone, is a minor component in the anal exudate that is discharged by the molested queens ( ). This compound is also a defensive allomone of an ant species (34), raising the possibility that it may possess general deterrent activity for arthropods. 

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