the quarantine facility in Gainesville, Florida. Flies were reared in a large self-contained,

climate controlled attack box exposing fire ants to attacks similar to the one described by

Vogt et al. (2003).

No-choice tests with native fire ants

 To determine whether the Formosa biotype of P. curvatus will actively attack and

develop in native Solenopsis fire ants, no-choice trials were conducted with S. xyloni and

S. geminata. Ten plastic trays (42 by 28 by 15 cm; Panel Control Corp., Detroit, MI)

were used in the no-choice tests, each with screened vents and tight-fitting glass lids

similar to those described by Porter and Alonso (1999). The trays contained a single solid

bottom covered with a 2-3 cm layer of moistened plaster to maintain high humidity.

Plaster was made by using a 1:1 mixture of pottery plaster (US Gypsum Co., Chicago,

IL) and plaster wall patch (DAP Inc., Baltimore, MD). Plaster was moistened before each

test run. Prior to moistening, the plaster bottoms were scraped to remove residues left

behind from previous use. When test trays were reused, native fire ants were not used in

trays that had been used by imported fire ants (and vice versa) unless the plaster bottoms

were replaced. This procedure avoided confounding results with odors previously

deposited on the plaster bottoms.

 Timer motors were used to automatically raise an inverted cup in one end of each

tray while lowering a cup at the other end of each tray. This caused the test ants to

continuously trail back and forth between the two cups. Timer motors were set to run for

8 h per d (10:00 to 18:00 h). A small piece of laboratory tissue (Kimwipes, Kimberly

Clark, Roswell, GA) moistened in IM sugar water solution served as a food source for

the flies and a bunch of artificial flowers in the center of each tray provided a perching

location. The laboratory was maintained at 27-280C.