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

Summary

Photo-attraction bioassay arenas are used to determine the optimal light color(s) to maximize insect attraction; however bioassays and methods are specific to target insect behaviors and habitats. Customizable equipment and modifications are explained for nocturnal or diurnal and terrestrial or aerial insects.

Abstract

Optimized visual attractants will increase insect trapping efficiency by using the target insect's innate behaviors (positive photo-taxis) as a means to lure the insect into a population control or monitoring trap. Light emitting diodes (LEDs) have created customizable lighting options with specific wavelengths (colors), intensities, and bandwidths, all of which can be customized to the target insects. Photo-attraction behavioral bioassays can use LEDs to optimize the attractive color(s) for an insect species down to specific life history stages or behaviors (mating, feeding, or seeking shelter). Researchers must then confirm the bioassay results in the field and understand the limited attractive distance of the visual attractants.

The cloverleaf bioassay arena is a flexible method to assess photo attraction while also assessing a range of natural insect behaviors such as escape and feeding responses. The arena can be used for terrestrial or aerial insect experiments, as well as diurnal, and nocturnal insects. Data collection techniques with the arena are videotaping, counting contact with the lights, or physically collecting the insects as they are attracted towards the lights. The assay accounts for insects that make no-choice and the arenas can be single (noncompetitive) color or multiple (competitive) colors. The cloverleaf design causes insects with strong thigmotaxis to return to the center of the arena where they can view all the options in a competitive LED tests. The cloverleaf arena presented here has been used with mosquitoes, bed bugs, Hessian fly, house flies, biting midges, red flour beetles, and psocids. Bioassays are used to develop accurate and effective insect traps to guide the development and optimization of insect traps used to monitor pest population fluctuations for disease vector risk assessments, the introduction of invasive species, and/or be used for population suppression.

Introduction

Almost all entomological surveillance depends on olfaction or visual attractants and often both. Volatile olfactory attractants may disperse throughout the environment resulting in a large attractive area. However, visual attractants may have a more limited range because of the invertebrate compound eye resolving images^1,2,3. Therefore, visual attractants must be optimized to the insect of interest to maximize attraction and the trap designed to take advantage of the target insect's natural behaviors.

Visual attraction is based on wavelengths f....

Protocol

1. Bioassay Components

1. Terrestrial arena construction
   1. Use metal flashing material strips of 2.54 cm length. Bend each strip into a half circle having a diameter of 15.24 cm (Figure 1).
   2. Connect the ends of each half circle and form a cloverleaf shape from the four pieces. Connect a locking nut and a #10 machine screw to the ends of each half circle to hold them together.
   3. Drill a hole at the midpoint of each semicircle 0.79 cm from the bottom of the arena. Affix 5 mm LED holders to the holes drilled in the middle of each semicircle.
   4. With the purpose of reducing reflec....

Results

The terrestrial arena has been used to improve pest monitoring traps for red flour beetles¹⁴ and the aerial arenas for hessian flies¹⁵ and biting midges⁷. Although the cloverleaf arenas were similar, the conditions for each insect species were different and accommodated the evaluation of nocturnal or diurnal insects that can crawl or fly. More importantly these lab studies translated into field applications for monito.......

Discussion

Photo-attraction bioassays are an important tool to determine the optimal attractive color(s) and minimize the options for field trials of these colors. However, several factors must be considered when optimizing the bioassay for a specific insect including: Single Light vs. competitive light experiments, brightness, optimal spectral range, ambient light interference, state of the insects, and natural behaviors that may limit the possible responses.

Most insects have some phototaxis, .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
metal flashing material
#10 stainless steel machine screw		Stock
#10 stainless steel locking nut		Stock
5 mm LED holder	Radio Shack Corp	276-080
matte black spray paint		Stock
Fluon		Stock
molded polyacrylic
screw top Nalgene	Thermo Fisher Scientific	Nunc polymethylpentene	125 mL, 64 mm outer diameter, 74 mm height
Threaded Teflon pipes		Stock	15 mm diameter, 60 mm length
StellarNet light spectrometer	Stellar Net, Inc	BLACK Comet C-SR-25
LED infrared light source	Tracksys LTD
infrared video camera	Panasonic Corp	WV-BP330 Panasonic CCTV camera
MEDIACRUISE software	Canopus Corp