Chemical signals species recognition

Optical fiber detectors (OFD) are devices that measure electromagnetic radiation transmitted through optical fibers to produce a quantitative signal in response to the chemical or biochemical recognition of a specific analyte. Ideally, an OFD should produce a specific and accurate measurement, continuously and reversibly, of the presence of a particular molecular species in a given sample medium. Additionally, OFD should pro vide maximum sensitivity and minimal interferences fromsuperfluous ions or molecules to obtain low detection limits. Other attractive features include the miniaturization of the fiber s tip to accommodate single-cell analysis and portable instrumentation to allow in situ analysis. 

The external cuticle of insects is covered by a waxy layer composed of mixtures of hydro-phobic lipids that include long-chain alkanes, alkenes, wax esters, fatty acids, alcohols, aldehydes, and sterols. The primary purpose of this layer is to maintain water balance and prevent desiccation, as described in Chapter 6, but many of the cuticular lipid components have important secondary roles as intraspecific contact chemical signals (pheromones). These roles include species and sex recognition during reproductive interactions, and nestmate recognition and other colony organization functions in social insects. Thus, these compounds are essential mediators of insect behaviors. Cuticular compounds are also exploited by parasitoids and predators as interspecific contact cues (kairomones) to aid in host location. 

Some individual or social behavioural patterns other than sexual phenomena, in marine animals belonging to the same species, are regulated by chemical signals, e.g. alarm, social recognition, tracking and migration. 

The coordination and integration of colony activities, in particular recruitment for foraging and defence, has been an essential contribution to the success of social insects the road to sociality was paved with pheromones (Blum, 1974). Pheromones play a central role in these activities and in other ftinctions such as recognition (of caste, sex, kin, colony, and species), caste determination, trophallaxis (mouth-to-mouth transfer of food), nest entrance marking and colony reproduction (Winston, 1992). Termites show convergent evolution of chemical signaling with the eusocial Hymenoptera. 

Atta sexdens, all attack intruders from alien colonies or species, but recognition at the species level takes place when the ants are separated by 0.5-1.5 cm, whereas the corresponding range for intraspecies recognition is 0-0.8 cm (Jutsum, 1979). This implies a difference in the chemical signals involved. 

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