821591.fig.001
Figure 1: Seminal events during the invasion of Solenopsis invicta and S. richteri in relation to their USA quarantined range. Since the introduction of S. invicta and S. richteri into the USA, efforts to contain and eradicate the ants have been attempted [2, 4]. The USA federal government emplaced a quarantine in May 1958 to limit the rate of range expansion of the ants. This quarantine is still enforced by the Animal and Plant Health Inspection Service (APHIS) today and prohibits movement of soil-containing products (e.g., sod, nursery stock, sand, etc.) or soil-moving equipment from a quarantined to a non-quarantined area unless first treated in an APHIS-specified manner to kill fire ants. The range values correspond to areas quarantined and do not relate changing population densities in the USA. Rather, the graph illustrates the expanding geographic range of these ants. Eradication efforts were attempted from 1957 through 1978 using several organochlorine insecticides (heptachlor, dieldrin, and mirex). Research efforts to discover, develop, and release pathogens and parasites as control agents in the USA resulted in identification and/or release of a microsporidian pathogen (Kneallhazia solenopsae) [18], viruses [2426], and Pseudacteon parasites [28]. Inset: S. invicta queen surrounded by workers and brood. Quarantine data were provided by APHIS [3] and the figure was adapted from Lofgren [29].