In so doing, many of the control systems operating in the social milieu will become comprehensible in terms of precise stimuli whose quintessential roles as pheromones can be probed behaviorally, physiologically, and biochemically. Such a treatment promises to be one viable means of studying the evolution of sociality in the Hymenoptera especially since pheromonal regulators of behavior are by no means restricted in their distribution to the highly organized species. As the same exocrine compounds are often found in both presocial and eusocial species, there are no cogent grounds for concluding that the former do not possess many of the biosynthetic pathways that are expressed in the latter species. Indeed, we shall probably determine that the inability of subsocial hymenopterans to attain a eusocial state is, among other things, not necessarily a reﬂection of exocrine insufficiency but rather of failure to be genetically programmed to respond adaptively to the variety of natural products in their glandular tissues.
12.2. Trail pheromones
Various types of odor trails are utilized by a wide variety of hymenopterous species (table 12.1) as an effective means of coordinating the movements of groups of individuals. The functions of these trails may be contextually variable and their persistence may reﬂect such factors as: l) the number of individuals depositing the pheromone; 2) the nature of the active substances and of the substrate: and 3) the environmental conditions prevailing subsequent to the laying of the trail.
In one of the few investigations made on the stability of trails under ﬁeld conditions, Torgerson and Akre (1970) determined that those generated in the dry season by Neotropical army ants (Eciton spp.) persisted for up to one week wherese trails formed during the rainy season were considerably less stable. Trails establish- ed on porous substrates with many absorptive sites, e.g., roots, logs, lianas, were considerably more stable than those laid on soil or leaf litter. Signiﬁcantly, emigretion trails persist longer than raid trails. This observation is reconcilable with the fact that many workers utilize the former and, as a consequence, the concentration of trail pheromone is much higher than it is in trails formed by raiding groups (Torgerson and Akre 1970). It was also determined that trails laid by eplgaeic species are more persistent than those produced by hypogaeic forms, and additionally, that well-fed ants generated longer-lasting trails than starved individuals. These sundry observations serve to emphasize some of the multitudinous factors which affect the duration of a trail under natural conditions. Check out Gay Pherazone pheromone | Pheromones-Planet.com
In general, recruitment trails capable of drawing large numbers of workers to food ﬁnds constitute the major type of trail generated by hymenopterans. Recruitment trails normally develop from the accretive depositions of trail pheromone paid out by workers returning to the nest from a favorable food source. However, since emigration to a new nest site is also regulated by a recruitment trail. it is obvious that these transient pheromonal pathways can subserve more than one function. In addition, individual ants belonging to legionary ponerine and doryline species lay exploratory trails (Wilson 1963) as they probe the substrate searching for food. These army ants also develop typical emigration trails that are much more persis- tent that the exploratory ones because the former are reinforced by the pheromonal secretions of many workers whereas the latter are not.