Insect communication is directed by a number of different pheromones. There are two types of pheromones commonly used by stored product insects and other urban pests: sex pheromones and aggregation pheromones.
Another broad category of chemical attractants are kairomones. These are chemicals produced by one species (insect or plant) that will attract a different species. It has a benefit for the receiving insect but will often disadvantage the organism releasing the attractant.
Sex pheromones are nearly always produced by the female to attract mates. These pheromones comprise specific compounds or a highly specific combination (blend) of compounds. Sex pheromones are usually produced by adults with short life spans of only a few weeks (e.g., stored food moths, cigarette beetle and warehouse beetles). The result of this short lifespan is that sex pheromones are highly active and attractive to male insects.
Male insects can be so sensitive to these pheromones that only a few nanograms (1 billion nanograms = 1 gram) can result in the male searching for the female. These pheromones can be active over a long distance and can draw moths with a plume of pheromone from several hundred feet away.
Aggregation pheromones are typically released by males and attract male and female individuals. They are produced in species with long adult life spans of several months to years (like most stored food beetles). Certain compounds of some aggregation pheromones are not species specific (e.g., flour beetles) and there is cross attraction, especially among closely related species (e.g., red and confused flour beetles).
The attraction distance of these types of pheromones are also much shorter than with sex pheromones (less than 15 feet). In most cases, foods synergize the effect of aggregation pheromones. Although aggregation pheromones increase the likelihood that an individual will find a mate, the roles of these substances as mating pheromones is not necessarily obvious. Aggregation pheromones attract insects to locations where mating occurs and where females find egg-laying sites on favorable food surfaces.
FOOD ATTRACTANTS & KAIROMONES.
Many food-based odors will enhance the attractiveness of pheromones when used together. Many economically important pests exist for which no sex or aggregation pheromone has been identified. In the absence of a pheromone, it is useful to substitute a preferred food source.
Imagine if a merchant grain beetle that was eating wheat all day and then detected odors from oat or carob oil. There would be a sudden rush to this new food source. Other obscure insects, like the Dermestid odd beetle, would quickly switch from consuming 100-year-old lambskin in old books to fresh, dry fishmeal.
In the absence of an available pheromone, offering a preferred food attractant instead, placed inside a pitfall style or sticky trap, can yield excellent results. In a few cases, food attractants have had better attraction than aggregation pheromones. Food attractants also can supplement captures by attracting the females that produce the pheromones.
Kairomones are chemicals that are produced by one species that attracts a different species and usually is for its own advantage. Recent investigations into bed bug attractants have shown several kairomones that are present in the sweat of humans, which would help with future bed bug lures.
David Mueller is a BCE with 35 years of experience. E-mail him at firstname.lastname@example.org.
Are Museums Drawing Insects Into Their Collections?
It’s a terrible day when a museum staff member finds evidence of an insect eating away at invaluable and irreplaceable material from their museum collection. Emotions can run high and panic can set in as they try to decide how large the infestation is and where it may be coming from. It is at this critical point, though, that it is best to remain calm and scientifically look at the problem.
Sex pheromones can prove to be a very valuable tool to pinpoint infestation sources in the situation above if the identified pest has a commercially available lure. Unfortunately, I have seen many institutions shy away from using pheromones only because they do not have all of the facts about them or they have been misinformed. Pheromone traps, when used correctly, will not draw unwanted pests into an area being monitored. Here are some facts about pheromones: The sex pheromone of common museum pests like,cigarette beetles, clothes moths and carpet beetles, will only attract the adult male insect. Sex pheromones that mimic the female insect will never attract a reproductive pair, the damaging larval stage or a female insect with eggs. The strength of the pheromone is generally not strong enough to pull from outside of the space that you are monitoring. Use the following guidelines to help you use pheromones to monitor and locate sources of damaging insect pests:
- First identify the insect that you would like to monitor.
- Make sure that the pest you want to monitor for has a viable, commercially available sex pheromone lure.
- During the monitoring period, keep the doors shut in the storage area that is being monitored. This will keep any and all pests from adjacent storage areas or outdoors from entering.
- Keep the pheromone lures at least 5 m (15 feet) away from any door that is being opened on a regular basis.
- Set up the traps in a grid pattern and once you start receiving numbers in the traps, adjust their locations to help you pinpoint the source.
- After pinpointing an area of infestation, use your eyes and other resources to locate the specific source.
Patrick Kelley is vice president of Insects Limited, Westfield, Ind. The firm develops, manufactures and distributes insect pheromones. Visit the firm’s website at www.insectslimited.com.