Pheromone plume

A third important characteristic of a female moth s sex-pheromone plume is its nonuniformity. Simulation of odor plumes using ionized air has shown clearly that a plume is not a simple concentration gradient but instead is distinctly filamentous and discontinuous (47,48). Furthermore,... 

Polkinghorne, C., Olson, J. M., Gallaher, D. G., and Sorensen, P. W. (2001). Larval sea lamprey release two unique bile acids to the water of a rate sufficient to produce detectable riverine pheromone plumes. Fish Physiology and Biochemistry 24, 15-30. 

Mafra-Neto, A. and R. T. Cardd. Fine-scale structure of pheromone plumes modulates upwind orientation of flying moths. Nature 369, 142-144 (1994). 

A widely held assumption is that there should be substantial competition among males to be the first to locate a calling female, and, therefore, there should be strong selection for behavioral traits in males that promote rapid location of calling females. These behaviors include (i) efficient ranging movements, that is, flight patterns (timed to coordinate with the females rhythm of calling) that sweep a wide area for the presence of a pheromone plume (ii) a low threshold for detection... 

As in most Lepidoptera, spruce budworm males locate conspecific females by flying upwind along a pheromone plume. The blends and release rates of these pheromone components form an important part of a specific communication system for the species. Once the communication system of an insect is understood, especially the pheromone chemistry as it relates to male behavior, it can be used in a variety of ways. For example, pheromones can be used to detect the presence of an insect in an area, to remove males from a population by trapping or poisoning and in air-permeation techniques in which the controlled and continuous release of pheromone components in the forest can disrupt mating. The latter use of pheromones appears to alter the normal male behavioral responses to the natural pheromone (16). 

Baker T. C. and Haynes K. F. (1987) Maneuvers used by flying male oriental fruit moths to relocate a sex pheromone plume in an experimentally shifted wind-field. Physiol. Entomol. 12, 263-279. 

Murlis J., Willis M. A. and Carde R. T. (2000) Spatial and temporal structures of pheromone plumes in fields and forests. Physiol. Entomol. 25, 211-222. 

If odor-evoked slow temporal patterns actually provide higher brain centers with information about the odor quality, identification and discrimination cannot be instantaneous as many of the temporal features in the response profiles appear late or even after offset of odor exposure. Honeybees need 500 ms for a response to (non-sexual pheromone) odors but at least 1 second of stimulation is required for a correct discrimination (J. Klein, unpublished, cited in Galizia el al., 2000a). Thus, it appears that time is an important factor in discrimination tasks involving non-pheromonal odors and the slow temporal patterns could theoretically contribute to an olfactory code. In contrast, these temporal patterns would be too slow to encode information about sexual pheromones. Male moths, for example, must be able to respond to rapid changes in stimulus intermittency when moving upwind in pheromone plumes in search of a calling female. 

Like many other insects, moths attract mates by long-distance pheromones. Females produce these pheromones in specialized abdominal glands. Chemically, they are acetates, often active in precise mixtures of geometric isomers. Males fly upwind, following the females pheromone plume to the somce, and mating ensues. In a typical experiment, a female moth, or just the pheromone, serves as odor source. An air current from that source helps to attract males who fly upwind to the pheromone source and attempt to mate. With this technique, we can compare the effects of known pheromones from different, related species on one species (species specificity). We can also test the attractiveness of different compounds that are stracturally similar to a known pheromone. In the laboratory, a wind tunnel, where available, is ideal, for this experience. 

Specifically designed olfactometers and wind tunnels have been widely used to measure orientation in a pheromone plume [280]. All these methods require sophisticated and expensive equipment and/or demand a large number of insects to achieve quantification of behaviour. 

Figure 7. a) Typical flight behaviour of a male moth tracking a pheromone plume released by a female moth, b) Trace of a typical pheromone search compared to the structure of the pheromone plume. (Image on top by Ishida Morizumi 2002 [40] bottom image by J.Hildebrand). 

Using both sensory systems, the male moth flies slowly upwind in the direction of the source when it finds a pheromone plume, performing a number of turns in a quite regular structure when the plume filaments are lost. 

In the MGC of M. sexta a small group of PNs has been found that appear to discriminate the duration and inter pulse of pheromone plumes at moderate frequency rates (10 Hz) [61]. 

K. A. Justus Bau and R.T. Carde, Antennal resolution of pheromone plumes in three moth species, J. Insect Physiol. 48 (2002) 422-433. 

JUSTUS, K.A., SCHOHELD, S.W., MURLIS, J., CARDE, R.T., Flight behaviour of Cadra cautella males in rapidly pulsed pheromone plumes. Phys. EntomoL, 2002, 27, 58-66. 

FADAMIRO, H.Y., BAKER, T.C., Helicoverpa zea males (Lepidoptera Noctuidae) respond to the intermittent fine structure of their sex pheromone plume and an antagonist in a flight tunnel. Physiol. EntomoL, 1997, 22, 316-324. 

Fig. 24.5 Field investigation of the sea lamprey sex pheromone to develop management application. (a) Researchers measure sea lamprey pheromones for a field trial, (b) A fluorescent dye (asterisk) is applied to measure a pheromone plume in the stream, (c) An ovulatory female sea lamprey is attracted to the source of the male pheromone (double asterisk tube opening hidden under the rocks), (d) Traps baited with sea lamprey pheromones (photos provided by Dr. Nicholas S.Johnson)...

Some differences in orientation behavior between crustaceans and flying insects are due to the slower ambulatory speeds of some of the animals that have been researched thus far (lobsters and crabs). In addition, the narrowness of close-range food-odor plumes that crustaceans respond to along the ocean bottom creates opportunities for left-right chemotaxis decisions that do not exist for tiny insects flying in very wide and fast-shifting pheromone plumes far from the source. 

THE EFFECTS OF CHEMICAL AND PHYSICAL FEATURES OF PHEROMONE PLUMES UPON THE BEHAVIORAL RESPONSES OF MOTHS... 

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