Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 17, 2001
Publication Date: N/A
Interpretive Summary: The red imported fire ant is a significant pest in the southern United States. Despite efforts to control this pest both the population and its range is expanding. This is due in part to the reproductive biology of the insect because females mate in flight and mated queens, that have the capacity of produce thousands of offspring, can travel many miles in wind currents before landing to start new colonies. Knowledge of the reproductive biology and physiology of the red imported fire ant is critical for development of novel methods to inhibit mating and establishment of new colonies. Scientists at the Center for Medical, Agricultural and Veterinary Entomology USDA-ARS, Gainesville FL. and Biological Control and Mass Rearing Research Unit, USDA-ARS. Mississippi State, MS have been studying the physiological mechanisms that regulate reproductive behavior and mating in these ants. They identified a hormone, juvenile hormone III , that acts to induce females to shed their wings. This hormone causes virgin females to shed their wings without leaving the mother colony and, thus, these females are unable to mate or start new colonies. This research may have considerable practical value for control of these dangerous ant pests because it may now be possible to inhibit mating and stop the establishment of new colonies by treating colonies with this hormone.
Technical Abstract: Analysis of extracts of hemolymph obtained from sexually mature alate females of Solenopsis invicta from monogyne colonies resulted in identification of juvenile hormone III (JH III). The average amount of JH III was 0.32 pmol/u of hemolymph. Topical application of 0.038 pmol of JH III was sufficient to stimulate alates to shed their wings in the presence of the queen. The time in which alates were induced to dealate decreased linearly with increasing concentrations of JH III from 0.038 to 3.8 pmol. However, higher JH III concentrations deviated from linearity and did not reach dealation times comparable with those that occur after mating flights. Thus, it appears that the mechanism of dealation that occurs when female alates are out of the influence of their queen is different from the one associated with mating flights. Application of 0.42 umol of precocene II inhibited dealation of alates in queenless colonies. However, this inhibition was reversed after applying 38 pmol JH III to precocene-treated alates. The sizes of corpora allata (CA) from sexuals treated with JH III did not differ from controls. However, the sizes of CA were reduced in alates treated with precocene II. The results indicated that JH was important to dealation.