Faa

428 identical to the cuticular hydrocarbons, enables returning foragers to locate the nest under the low light conditions of the cavity (Steinmetz et al., 2002, 2003).

Among non-social insects, trail-marking pheromones are well known in cockroaches and gregarious caterpillars. For example, the trail-marking pheromone of P. americana serves to aggregate both adults and juveniles. Among Lepidoptera, trail-marking pheromones are released by gregarious caterpillars in diverse families, for example, the forest tent caterpillar (Malacosoma disstria) (Lasiocampidae), the pine processionary caterpillar (Thaumetopoea pityocampa) (Notodontidae), and Hylesia lineata (Saturniidae) (Fitzgerald, 2003). Trail pheromones are also produced by the gregarious larvae of the redheaded pine sawfly (Neodiprion lecontei) (Flowers and Costa, 2003). In these examples, the trail pheromones are used to recruit conspecifics to a feeding site, to enable foragers to return to the colony, and to maintain colony integrity, especially when the colony as a whole moves to a new location.

Knowledge of the chemistry of trail-marking pheromones is almost entirely confined to those of social insects. In termites and many ants they appear to be mixtures oflong-chain fatty acids, alcohols, aldehydes, esters, or hydrocarbons (Figure 13.7E). However, within these mixtures one or two compounds are typically the major component. For example, of the 10 components identified in the trail pheromone of the ant Mayriella overbecki only one, methyl 6-methylsalicylate elicited trail following (Kohl et al., 2000). Varying degrees of species specificity are observed. For example, species of Solenopsis (fire ants) have a common pheromone, and among leafcutting ants (Atta spp.), species will follow the trails of congenerics. In contrast, the Argentine ant, Iridomyrmex humilis, follows a trail of (Z)-9-hexadecenal but not of its geometric isomer, (E)-9-hexadecenal.

4.1.6. Spacing (Epideictic) Pheromones

A relatively new discovery in pheromone research are those pheromones that stimulate insects to spread out so as to maintain an optimal population density. They may be produced by immature and adult insects and may be olfactory or tactile. Spacing pheromones have been best studied in relation to oviposition. For example, after laying, the female apple maggot fly, Rhagoletis pomonella, releases a pheromone that deters oviposition on the fruit by other females (Prokopy, 1981). The pheromone appears to be released from the hindgut as the ovipositor is dragged over the fruit. It appears to be a water-soluble peptide that remains biologically active for several days after deposition.

Several Lepidoptera also produce oviposition-deterring pheromones that limit the number of eggs laid on a given plant (Schoonhoven, 1990); further, the presence of feeding larvae of Pieris brassicae inhibits egg laying, suggesting that the larvae also produce a pheromone. In the case of the flour moth, Anagasta k├╝hniella, meetings between larvae result in the release of pheromone from their mandibular glands. Above a certain level of pheromone, reflecting the number of encounters and hence the density of larvae in the medium, adult females will not oviposit. However, oviposition is stimulated at low pheromone concentrations which are indicative of a medium suitable for larval development but not overcrowded.

As noted in Section 4.1.3, bark beetles produce an aggregation pheromone to ensure a "collective effort" when initially attacking new host trees. However, resident females subsequently release a spacing pheromone (verbenone) whose function is to reduce conspecific competition for egg-laying sites so that the output of each female is not compromised (Borden, 1982).

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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