LONG-TERM STUDIES OF THE BLACK IMPORTED FIRE ANT (HYMENOPTERA, FORMICIDAE) INFECTED WITH A MICROSPORIDIUM

For 4 yr, we studied the host-pathogen relationship of the microsporidium Thelohania solenopsae Knell, Allen, and Hazard within field populations of the black imported fire ant, Solenopsis richteri Forel, in Argentina. We established and monitored 6 field plots having a high density of fire ant colonies, many infected with the microsporidium. The density of colonies, initially 162 colonies per hectare, decreased to 28 colonies per hectare. The percentage of infected colonies, initially 22.4%, increased to 35.7% and was negatively associated with the density of colonies but positively associated with rainfall. T. solenopsae was the only known natural enemy of fire ants present consistently and in high levels within the plots. We suspect it is one of the main factors responsible for decreases in S. richteri population densities.