What Are Aggregation Pheromones?

In insects, aggregation pheromones are chemicals released by an individual that induce conspecifics to aggregate. Chemically, aggregation pheromones are often structurally related to alarm pheromones. In general, the terms "alarm pheromone" and "aggregation pheromone" can be used interchangeably. The two terms are usually associated with different behaviors in different species of insects. For example, in cockroaches, the aggregation pheromone (2-methyl furan) elicits aggregation behavior, while in termites, the alarm pheromone (4-methyl thiophenol) elicits both aggregation and avoidance behaviors. However, there are exceptions to this rule; for instance, in the American cockroach Periplaneta americana, both 4-methyl thiophenol and 2-methyl furan elicit only aggregation behavior.

How Do Aggregation Pheromones Work?

When an individual insect detects aggregation pheromones, it will change its behavior in order to join the group. The mechanism by which this occurs is not fully understood, but it is thought that aggregation pheromones stimulate a change in the brain that leads to alterations in walking speed and changes in surface substratum preference. Additionally, some evidence suggests that aggregation pheromones may also increase the likelihood of an insect encountering other conspecifics by altering their attraction to certain areas. It is important to note that not all insects respond to all types of aggregation pheromones; for example, moths of the same species may use different types of aggregation pheromones depending on the time of year.

What Are Some Examples of Aggregation Pheromones?

One well-studied example of an insect that emits aggregation pheromones is the German cockroach Blattella germanica. This cockroach produces a variety of compounds that function as both alarm and aggregation pheromones. These include long-chain alkenes such as geranial and neral, short-chain alkanes such as tricosane and heptacosane, and terpenes such as limonene and 3-carene. Another example of an insect that uses aggregation pheromones is the black house ant Monomorium minimum; this ant produces 2-ethylphenol as its primary aggregation pheromone component.

Insects use a variety of chemicals—known as pheromones—to communicate with one another. One type of pheromone that has been studied extensively is the aggregation pheromone. Insects release these chemical signals in order to induce conspecifics to aggregate, or come together in groups. There are many different examples of insects that use various types of aggregation p her om ones; some well-known examples include German cockroaches and black house ants. While the exact mechanisms by which these chemicals alter behavior are not fully understood, scientists believe they play an important role in social interactions among insects.