What is an insect pheromone?  -->  It is one of the "languages" of insects.

Many insects communicate with each other using chemical substances called "pheromones", whereas human beings communicate mainly with languages. In the sense, insect pheromones may be regarded as insect language. To understand this insect language, we must translate the pheromones into human language.

II. Pheromones and the monitoring of insects

In trying to understand the meaning of pheromones as language, we can use the pheromones to get information on an insect species. If a pheromone means "come here", it could be used to call together many individuals. A sticky device using this pheromone could capture many individuals attracted by the pheromone. The number of catches would be provide much information about the insects.

III. Pheromone to call together: Come here!

Many insect pheromones have been identified and classified into numerous groups on the basis of their meaning as language. In many cases, the sex pheromone and the aggregation pheromone mean "come here". Thus, these two pheromones are suitable for use in a monitor.

IV. The sex pheromone and the aggregation pheromone

Both the sex pheromone and the aggregation pheromone work as a language to call individuals together. However, the use of the sex pheromone as language is subtly different from that of the aggregation pheromone. Stored-product insects using a sex pheromone have a high activity to that pheromone, whereas stored-product insects using an aggregation pheromone have a low activity to that pheromone.  This difference depends mainly on biology and behavior. For example, adult male tobacco beetles feed nothing under storage conditions and so their longevity is at most two weeks. During this time, they fly actively in search of females and are strongly attracted to the sex pheromone in order to mate with females during the limited time available. In contract, adult red flour beetles stay in the same habitat as when they were larvae, feed adequate food and have relatively long lives of over 200days. Aggregating in the habitat, males can find females and mate easily. Their aggregation pheromone works within the habitat, so its effectiveness as an attractant is not very high.

Table 1. Relationship between pheromone types and behavior and biology of stored-product insects

Type of   pheromone Activity to the pheromone Behavior Adult feeding Adult longevity Typical insects   Sex   pheromone High Fly NO short Tobacco beetle   Aggregation   pheromone Low Crawl YES long Red flour beetle

Nakakita (1998) "Shokubustu boueki kouza (3rd edition)" P. 345 - 346

V. Attractancy of pheromones

When many individuals are captured by a pheromone, can we say that the pheromone had high attractancy? Many individuals could be captured by a device placed near them, even though the pheromone had low attractant activity. When a monitoring device captures individual insects originating far from the device, this confirms that the pheromone has high attractancy. Therefore, the attractancy is not the number of captures, but rather the effective distance from which individuals could be attracted.

VI. Monitoring by the sex pheromone and the aggregation pheromone

Many sex pheromones have high attractancy and so have a long effective distance (r) and/or a wide effective area. However, aggregation pheromones have low attractancy and so have a short effective distance and/or a limited effective area. When we use these two pheromones as attractants for monitoring devices, we have to develop different usage on the basis of the different attractancy levels of each pheromone.

VII. Effective monitor with aggregation pheromone

Monitor with pheromone is typically used to estimate the number of individuals, or to determine the source of infestation for a whole area. The aggregation pheromone has lower attractancy than the sex pheromone, and therefore, when monitor with aggregation pheromone, special techniques are required to realize a monitoring accuracy similar to that achieved for monitor with sex pheromone.

1. Increase the number of devices placed in an area
	A Monitor with pheromone is just like a radar site. If each "radar" has a limited searching area, many radars are required in order to search the whole area for insects. This is because when the number of radars is not sufficient in an area, many insects will pass through the radar network undetected.
2. Reinforce of the monitor with aggregation pheromone
	The limited attractancy of the aggregation pheromone means that an insect voice using this "language" reaches a limited area. In a similar situation, a man can use a loudspeaker to expand his voice to cover the whole area. What kind of substances would work like a loudspeaker? Food attractants are promising candidates as loudspeakers, because insects tend to be attracted to food. Then, the aggregation pheromone is often used together with a food attractant in a monitoring device.

VIII. Future development of monitoring devices with pheromone

We have developed various kinds of monitoring devices with pheromone based on an analysis of each pheromone as "insect language". Furthermore, by taking insect behavior and biology into account, we have developed many specially designed monitoring devices with pheromone. We believe that pheromones are suitable for use in monitoring devices as "radar" sites or as a tool for communication with insects. We are continuing to develop new monitoring devices with pheromone based on a detailed understanding of pheromones as "insect language".