The effects of long-wavelength infrared radiation on the flying activity of stable flies, Stomoxys calcitrans (L.)

Abstract

Stable flies, Stomoxys calcitrans (L.), were exposed to infrared radiation to determine if they respond to such radiation emitted by cattle and other warm-blooded hosts. The infrared radiation was emitted from a spherical cavity at temperatures of 100° and 115°F, and the magnitude and wavelength of the incident radiation of the flies were approximately the same as that received by surfaces at 10 to 40 feet from a cow. Exposures to the infrared radiation were made with both sexes of stable flies, in both darkness and light, and at 75° and 80°F. Responses to the infrared radiation were determined by counting the flights made by stable flies confined in test cages. Flights were counted by detecting the electrostatic charges on moving flies with electrometer electrodes in the center of the conducting cages. The signals generated during insect flights were amplified and electronically counted or recorded for later counting. Eleven separate and independent experiments were performed with different combinations of sex, visible light, and air temperature. Each experiment compared the number of flights made during exposure to the number made during a similar period without radiation. Each experiment was designed as a modified 4 by 4 Latin square, and an experimental unit was either 5 or 10 flies confined in a test cage for an hour. In addition to colonized stable flies, wild stable flies were also used. Also, a few tests were performed in an attractancy chamber. No response to infrared radiation was observed in any of the experiments. In 7 of the 11 experiments, the irradiated flies made more flights than the non-irradiated flies, but none of the differences were statistically significant. The conclusion drawn from this investigation is that stable flies are not responsive to incident infrared radiation such as that emitted by cattle to surfaces more distant than 10 feet. At closer distances or with greater irradiance, infrared radiation sensitivity of stable flies may be confounded with sensitivity to air temperature gradients.