Environmental components of pupariation-site selection by the stable fly (Diptera: Muscidae)

The effects of moisture, temperature, light, pH, and osmolality on pupariation-site selection and survival of stable fly, Stomoxys calcitrans (L), pupae were evaluated by means of choice tests on an artificial medium with different levels of these parameters. Of the moisture levels tested (50, 68, and 89%), more pupae were found at 68%. Wandering larvae pupariated in the dark, when placed in a light gradient, and at a temperature of approximately 27 degrees C, when in a temperature gradient. When given a choice of pH levels 5.2, 6.4, 7.2 or 9.3, wandering larvae pupariated at the highest pH. Conversely, they pupariated at the lowest osmolality when given a choice of 111, 254, 403 or 609 mmol/kg. Distribution of pupae in uniform medium was found to be nonrandom. Laboratory-reared larvae released in a feedlot dispersed up to 9.1 m, but they did not appear to relocate under the more suitable conditions. Naturally occurring pupae were found in a wider range of the above habitat parameters. This implies that other selection pressures aside from the measured environmental parameters are also important in the selection of pupariation sites