Trail pheromones orientation

I review the role of trailing in these social activities, discuss how snakes orient to pheromone trails and describe some aspects of the evolution of trail pheromones. 

The term recruitment , like the term alarm has become diffuse as the diversity and complexity of social insect behavior has emerged. In this review we will take recruitment to mean the inducement of workers to move from one area to another, either to retrieve food or to move to new territory or a new nest site. The chemical signals involved are usually, but not always, deposited on the substratum, and may therefore also constitute an orientation signal. The two possible functions of trail pheromones , recruitment of nest mates and orientation to food or nest, need to be carefully separated to estimate the importance of these chemical signals in the ecology of each species. 

Compared to alarm pheromones, very few trail pheromones have been characterized chemically this reflects the extremely low levels of compound present in the trail secretions of most species investigated. The confirmed structures are shown in Fig. 15.10. In many cases only a single compound has been identified, usually one which stimulates both recruitment and orientation. These compounds are normally stored and applied in highly dilute aqueous solution, and... 

We believe these results support a false-trail-following theory for the mode of action of mating disruption. The fact that males were able to discern and orient to a strong releaser while in the center of areas treated for disruption, demonstrates that omnipresence of pheromone vapor per se is not always adequate to achieve mating disruption. Rather, the key factor appears to be the relative strength of the pheromone signals produced by trap-baits - or female moths - versus those produced by disruptant particles. 

It was originally reported that pheromone trails might guide rattlesnakes to their dens in the fall (Klauber, 1972). However, it now appears that only juveniles and yearlings use trails and that adults may rely on other orientation mechanisms. Brown and MacLean (1983) documented juvenile timber rattlesnakes (Crotalus horridus) following adult pheromone trails in the fall (Table 3), but King et al. (1983) found that adult prairie rattlesnakes ( viridis, would not trail conspecifics. Adult Crotalus apparently find dens by celestial cues (Landreth, 1973, Duvall et al., 1985) and... 

A). When the male encounters a trail, he chemosensorily assays these objects (TFs), detects more pheromone on the side in the direction the female went, and then uses chemotactic orientation to follow the substrate trail (Fig. 6, B). 

In these cases, orientation of scouts is probably achieved without the use of pheromones. However, recruitment by tandem-running in Camponotus sericeus is guided by an orientation trail previously laid by scouts from their hind-guts (HOlldobler et al., 1974). 

AGO methods provide efficient heuristic algorithms to solve TSP (see [4,3]). However, they also suffer from some intrinsic problems. On the one hand, let us note that this method lies in the idea that pheromone trails interact with each other in such a way that good paths are cooperatively constructed by ants. However, this characteristic is twofold. Sometimes paths may interfere and damage each other. For instance, local cycles involving only some nodes may be created and, even worse, be reinforced by subsequent ants. On the other hand, sometimes a local oriented method hke AGO may miss some simple graph peculiarities such that, if they were taken into account, then they would allow to easily find better paths. For instance, when a better path is found by ants, it takes a lot of subsequent ant movements to reinforce the new path until it is actually preferred to other older weU-estabhshed paths. 

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