A 2005 study conducted by Sela et al. utilized green fluorescent protein (GFP)-tagged E. coli placed in fruit fly feeding solution to show that flies inoculated with GFP-tagged E. Coli was able to harbor the bacteria for up to 7 days following contamination. This finding showed that the medfly has the potential to be a vector of human pathogens to fruits. Aggression Studies have shown that wild C. capitata flies were found to partake in more head-butting behavior, direct opponent contact, and less likely to cede an occupied leaf to an invader. Furthermore, it was found that sounds that are produced during body vibration constitutes threat behavior. Aggressive sounds are substantially higher in pitch (roughly around 1–3 kHz) while sounds produced during non-aggressive moments such as courtship times tended to be around 0.16-0.35 kHz. Aggressive behaviors can be observed during the courtship ritual. If the approaching fly is discerned to be an intruder male fly, the resident male fly terminates his calling position and lunges towards the intruder, physically pushing the intruder with his head. This interaction lasts until either party loses position or eventually leaves the position. Males can also partake in passive defensive actions which consists of a “face-off” with the intruder male rather than a physical “head-butt”. Males in the “face-off” position can last up to 5 minutes until one male eventually turns and leaves the territory. Invasions and eradication In the United States, C. capitata has invaded four states (Hawaii, California, Texas, and Florida) but has been eradicated from all but Hawaii. However, reintroduced populations of the medfly have been spotted in California as recently as 2009, requiring additional eradication and quarantine efforts. It has also been eradicated from New Zealand and Chile. Eradication efforts in Mexico and Guatemala Medflies were first detected in the region in Costa Rica in 1955. From then on, the medfly spread northward, reaching Guatemala in 1976 and Mexico in 1977. In order to begin eradication efforts, the Mass-rearing and Sterilization Laboratory was producing 500 million sterile flies weekly by the end of 1979. By releasing these sterile flies into the wild, scientists were able to not only prevent the northward spread of the fly, but officially declare it as eradicated from all of Mexico and large areas in Northern Guatemala in September 1982. Eradication efforts in Western Australia Utilizing the Sterile Insect Technique, the medfly was eradicated in December 1984