|Behavior and Semiochemicals|
Dr. Vander Meer used a queen produced worker attractant pheromone, invictolide, as a model for the use of attractants in fire ant baits. The following were determined: 1. monogyne and polygyne fire ant workers respond equally well to queen-produced attractant pheromones. 2. Significant attraction was obtained when the racemic queen pheromone (invictolide) was dissolved in the bait phagostimulant, soybean oil and absorbed in carrier grit particles. 3. Fire ants discover pheromone enhanced baits significantly faster than non-enhanced baits, and in paired tests enhanced baits are discovered first up to 75% of the time. 4. Paired single mound treatments demonstrated that pheromone enhanced baits gave more rapid control then non-enhanced baits. This research demonstrated the concept and benefits of attractant-enhanced baits. While invictolide is difficult to synthesize and is therefore expense, we later discovered and patented a natural attractant, 2,4-heptadienal, which is commercially available. We anticipate that this compound will enhance fire ant baits.
Vander Meer, R.K. and Lofgren, C.S. 1999. "Attractant for Social Pest Insects". United States Patent No. 5,897,859.
View the slide show Attractants for Social Insects
Dr. Vander Meer and colleagues discovered a number of effective fire ant repellents. A patent application was filed and four patents have issued covering several classes of compounds. The repellents are generally volatile compounds that will require a slow release formulation in order to extend the active life of the repellents. Controlled release formulations of the volatile repellents are now being pursued through a Cooperative Research and Development Agreement with BioGuard, Research and Development, Inc., who have available proprietary sustained release technology. While these compounds do not kill fire ants, they do provide the opportunity to exclude ants from areas where they are not wanted without the use of insecticides. Potential applications include urban picnic areas, high human use places in parks and recreational areas, plant nurseries, hospitals, electrical equipment, interstate commerce, etc. Additional commercial interactions are being sought to develop controlled release formulations of these volatile compounds.
Nestmate recognition is a key element in the organization of social insects. We have made many discoveries that have been important to the understanding of nestmate recognition in ants. Recognition of intruders (other ants, pathogens, parasites, predators) as non-nestmate, triggers colony defenses that protect the colony from invasion. Knowledge of nestmate recognition enabled us to decipher how two fire ant parasites are able to integrate into the highly aggressive fire ant colonies. This work has had a major impact on hymenopteran nestmate recognition research. "Cracking" the nestmate recognition code for the fire ant will help us to more effectively introduce parasite, pathogen, and/or predator biological control agents, as well as biologically-based population suppression technologies.
BSF Grant No. 1999089 (1999-2003):
A co-principal investigator in Israel and Dr. Vander Meer have started to investigate the effect of social environment and biogenic amines (neurotransmitters) on conspecific aggression. We have developed a novel method for the analysis of biogenic amines that utilizes gas chromatography and mass spectrometry. The method will be used to determine the role of biogenic amines in modulating fire ant nestmate recognition abilities. The results of this work will bring our understanding of nestmate recognition to a new level, and in addition, modification of nestmate recognition behavior in the fire ant or other pest ants could provide novel biologically-based control alternatives and aid classical biocontrol. Regulation of biogenic amines could be the key to how the queen influences/controls worker behavior through primer pheromones.
NRI Grant No. 98-35302-6983 (1998-2002): Behavioral Mechanisms Underlying Polygyny in Fire Ants.
The origin of polygyne fire ant populations is unknown, but is important because they have multiple queens per colony, ca. three times the worker density compared to monogyne populations, and are thought to be more difficult to control. We previously demonstrated that orphaned workers from monogyne or polygyne colonies readily adopt newly mated queens, and that this adoption phenomenon could be part of a mechanism leading to the development of polygyne colonies. Another mechanism could be effected through claustral colony foundation of several queens of both polygyne and monogyne origin. We discovered that polygyne-derived queens have a significantly lower success rate in founding colonies. The final results are still being monitored.
Phorid flies represent a sustainable biological control agent against fire ants but are labor intensive to rear in the laboratory; therefore, increasing phorid fly rearing efficiency is very desirable. Drs. Vander Meer and Porter have investigated how the parasitic fly interacts with its fire ant host. We previously discovered that fire ant workers release exocrine gland products that attract phorid fly parasites and we now have determined that the active compounds are fire ant alarm pheromones released from their mandibular glands. Once the active compounds are isolated formulations can be developed to increase rearing efficiency, and to devise effective detection traps.
We have used electrical stimulation of fire ant workers (releases phorid fly attractants) to determine if this will increase P. tricuspis rearing productivity. This method had the following effect on phorid fly rearing: Mean of 30% more attacking flies; Mean of 15% fewer resting flies; Mean of 20% increase in parasite pupae production. Isolation of the active compounds will provide an easier route to these rearing benefits.
Isolation of the active comopunds is also important to the development of phorid fly traps. Traps have the following potential benefit: Detection of incipient fly populations; Focus flies to a desired area; Biotype selection in South America; Collection of "wild" flies for rearing enhancement; and Research.