Incidence of the screwworm, Cochliomyia hominivorax, and the secondary screwworm, C. macellaria (Diptera: Calliphoridae), in the central highlands of Chiapas, Mexico.

Abstract

In a 12-month survey in the central highlands of Chiapas (470 to 2,270 m elev.), 100 adult screwworms, Cochliomyia hominivorax (0.058 adults/trap-wk), and 1,155 adult C. macellaria (0.671 adults/trap-wk) were captured in wind-oriented traps baited with swormlure-2. Trap captures of these 2 species were not correlated with elevation; instead, adults appeared to occur in “pockets” along the altitudinal gradient. More adults of both species were captured during the wet season than in the dry season, and seasonal differences in captures were greater at elevations from 1,470 to 2,270 m than from 470 to 1,270 m. Adult capture rates (ACR) for screwworms were not correlated with average monthly temperature or rainfall at the low elevations but showed a positive correlation with average monthly temperature and rainfall at the high elevations. These differences in ACR between the high and low elevations were believed to be due to the greater annual changes in weather at the high elevations. ACRs for C. macellaria were not correlated with average monthly temperature or rainfall at either the high or low elevations. Screwworm oviposition showed a negative correlation with elevation (P < 0.05), a possibly significant negative correlation with average daily rainfall (P < 0.10), and a positive correlation with temperature (P < 0.05); however, oviposition was observed at the highest (2,060 m) and coldest (16.1 °C average daily temperature) sampling site.