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 microsporid ium Thelohania solenopsae Knell, Allen, and Hazard within field popula tions of tile black imported fire ant, Solenopsis richteri Forel, in A rgentina. We established and monitored 6 field plots having a high den sity 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, initiall y 22.4%, increased to 35.7% and was negatively associated with the den sity of colonies but positively associated with rainfall. T. solenopsa e was the only known natural enemy of fire ants present consistently a nd in high levels within the plots. We suspect it is one of the main f actors responsible for decreases in S. richteri population densities.