Long-term stability in the mating system of the bot fly Cuterebra austeni (Cuterebridae)

The bot fly Cuterebra austeni exhibits year-to-year consistency in its landmark-based hilltopping mating system. Flies were found on some of the same localized ridgetop perching areas that were known to be mate encounter sites 22 years previously. In both 1980 and 2002, males were drawn preferentially to locally elevated, largely vegetation-free sites. In addition, a substantial proportion of individuals exhibited site fidelity in both years, as demonstrated by their willingness to return to the site where marked after being captured and handled. In both years of observation, a smaller proportion returned the second day after marking and only 1020% of marked males were seen on the third day. Thus males apparently have only a very limited window of opportunity to secure a given perching territory. In both years, a number of males ("residents") succeeded in monopolizing a perching area over a substantial part of the brief morning flight period. One unexplained difference across the decades: residents appeared on a lower proportion of days of observation in 2002 than in 1980.