Key Elements of Photo Attraction Bioassay for Insect Studies or Monitoring Programs

This method can help answer key questions in insect surveillance and control, by improving the attraction of existing traps and incorporating colors or lights into the design of future monitoring and control traps. The main advantage of this technique is the initial evaluation of attractive colors and insect behaviors in the lab, prior to the costly and time consuming tests in the field. Insects have innate behaviors or instincts that should be used to make monitoring and trapping more effective.

The bioassay arena is designed to be a flexible method to evaluate behaviors in any insect species, prior to field trials. This protocol uses an aerial arena, but a terrestrial arena design is also available. The critical difference between the aerial and terrestrial arena's is the use of vertical space, which changes the size of the arena.

When selecting an arena type for an experiment consider the insect species being studied. The aerial arena has the ability to capture insects in a collection container, whereas the terrestrial arena is a two dimensional object and really is designed for recording visits to the lights. To begin, disassemble and clean the aerial arena with an odorless, non abrasive soap and warm water.

Then dry the arena and allow it to finish air drying. Before each experiment record the pertinent environmental conditions, and monitor any trends that occur from experiment to experiment. First, use four supports and black linen cloth to set up a pedestal.

Then place the arena baseplate on top of the pedestal and assemble each piece of the arena on the baseplate. Next, place the cloverleaf arena around the central release point in the baseplate. Then install the LEDs into the LED holders of the four collection containers, and set up the electrical equipment to control the lights.

To prepare the arena for a competitive experiment, position LED lights with distinct characteristics on each cloverleaf. The arena set up is the most important and critical factor, because simple changes in the arena can alter the insect's behaviors. Therefore, many factors can be changed or altered to address insect behaviors, such as photo attraction.

Behaviors with feeding, so blood fed, or sugar fed or starved. Different life history stages or different physiological responses. Next, to control for potential effect of light interference or environmental preferences, rotate the light positions after every replicate.

Refer to the text protocol for further information on filming devices. First place the clear lid over the arena, parallel to the baseplate. Then introduce immobilized midges to the arena.

After the experimental period record the pertinent environmental conditions. Finally, after euthanizing the midges count the responders in each collection container. In this study the movement of red flower beetles was evaluated in a competitive style terrestrial arena for five minutes, and filmed with an infrared camera.

Test colors included blue, and three wavelengths of UV light. The trial data indicated that the beetles were most attracted to near UV light with a wavelength of 390 nanometers. The movement of Hessian flies was also evaluated in a competitive style aerial arena with a diurnal setting.

The lights were most attracted to lights in green wavelengths with high intensities. Female flies preferred the green spectra of 502 and 525 nanometers. While both sexes preferred the high intensity 16 watts per square meter light.

Biting midges were also tested in the aerial arena under nocturnal conditions, to determine optimal attractive colors. The highest proportions of midges were attracted to UV light, with the brightest lights being the most attractive. Once mastered, the photo attraction bioassay can be used to rapidly assess insect behavior, prior to costly and labor intensive field trials.