Light Preferences by Insects in Two Different Mountain Habitats

Light Preferences by Insects in Two North Carolina Mountain Habitats

Kirk James and Benjamin Smith

Field Biology and Ecology, Dr. Michael Baranski

Abstract

This study was a determination of which of six wavelengths of light was preferred by different orders of insects. Using six different fluorescent lamps placed on tubs with a soapy water solution, two contrasting sites in Ashe County, NC were tested. The first trial was conducted at Mount Jefferson, a high-elevated area. The second was performed at a lower elevation, New River. The trials were conducted at night and the insects were collected and placed in jars of rubbing alcohol after the lamps had been on for approximately 40 minutes. The number of insects found in each tub under a specific type of light was determined and recorded. Using partners, the orders of the insects were identified and recorded on a data table. The overall results combined from both locations show that the greatest number of insects was found in the black-light traps followed by the green-light trap, white-light trap, blue-light trap, yellow-light trap, and red light trap.

Background

Everyone has seen insects circling street lamps, door lights, and other sources of artificial light at night. More than likely they have seen a bug-zapper with its fluorescent light and the metal grill pulsating with electricity waiting for the next victim to fall prey to its luring effect. Insects are attracted to the light, which helps them to navigate, but in an attempt to keep the same portion of their eyes illuminated by the light they either spiral into the light or around it continuously (Benedikt 2000) . They are able to see longer wavelengths of light than we are and are able to differentiate among different wavelengths. Insects can see from 300-400 nm (near ultraviolet) to 600 –650 nm (orange). There are two peaks in wavelength activity, one at 350 nm (near ultraviolet) and another at 500 nm (blue-green). It is believed that insects react to the ultraviolet wavelengths because ultraviolet light is absorbed by much of nature, especially by the green foliage. Anytime there is ultraviolet light, then there must be open space so they fly towards it and end up being deceived into believing that something is there that really is not (Matthews 1988).

Research Problem

The experiment was designed to determine insect preferences for different wavelengths of light. The experiment was done twice at two different elevations to compare insect diversity at the two different locations.

Methods

We conducted an insect-trapping experiment using six types of light, five of a specific wavelength and one of white light. Fluorescent lamps were used with six different colored light bulbs: red, yellow, green, blue, white, and black. The fluorescent lamps were placed over a medium sized tub that contained a soapy water mixture so that the insects would suffocate on contact with the solution. The lamps were run for approximately 40 minutes. The experiment was conducted on two different nights in two different habitats, both located in Ashe County, North Carolina. The first night the experiment was set up on Mount Jefferson at 10:30 PM. This location was at a high elevation (3600 ft) with a lot of wind and a cool temperature ranging from 50-55 degrees Fahrenheit. The second night the same apparatus was set up at the New River at 9:40 PM. This location had a warmer air temperature at 62 degrees Fahrenheit, less wind, and a lower elevation (2000 ft). After the insects had been collected, groups of two people work ed together and removed the bugs from their designated tub. The insects were placed in a separate jar filled with rubbing alcohol. The jars were labeled according to the color of light to which the insects were drawn. Later in the lab, the insects in each jar were sorted according to insect order. The number of individuals in each order was recorded in a data table.

Results

Table 1. Number of insects drawn to each type of light

Mount Jefferson

ORDER

RED

YEL

GREEN

BLUE

WHITE

TOTAL

New River

ORDER

RED

YEL

GREEN

BLUE

WHITE

TOTAL

Fig. 1. Percentage of total insect collection for both locations drawn to each type of light

During the Mount Jefferson trial, a total of 700 insects were captured (Table 1). The highest number of insects was found in the black-light trap (450), followed in descending rank (highest to lowest) by the green-light trap (127), blue-light trap (68), white-light trap (40), yellow-light trap (6), and red light trap (5). During the New River trial, a total of 939 insects were captured (Table 1). The highest number of insects was found in the black-light trap (680), followed in descending rank by the white-light trap (110), blue-light trap (78), green-light trap (43), yellow-light trap (21), and red-light trap (7). For both of the locations combined, the black-light trap (1130) captured the most insects followed by the green-light trap (170), white-light trap (150), blue-light trap (146), yellow-light trap (27), and red-light trap (12).

Conclusion/Discussion

The original data was manipulated because there appeared to an error in labeling the jar for each light source for the blue and black light collection. On that note the data seems to compare better with the previous research that show insects to be more attracted to the black light. The wavelength of black light is very close to those of that of UV rays attracting them with the false sense of open area. The attraction of green and blue-lights can be related to the fact that they are short like the black light and because of their photosynthetic relation. When a insect receives these wavelengths of light they might believe that they are near a plant and near a food source for the vegetation supplies a good source of food. The red and yellow-lights didn’t pick up that many insects because the light didn’t travel as far as the others and the insects weren’t attracted to it first. The white light presented all the colors of the spectrum, and insects have a moderate attraction to it. For not only did the white light travel far but also it drew them for they picked up on the red, yellow, orange, green, blue, indigo and violet wavelengths and were more than likely confused by the wide variation in wavelengths. From the data we concluded that insects are drawn to by shorter wavelengths of light than to longer wavelengths of light can be drawn. The Chi-square shows that there is a significant difference in the number insects in various light wavelenghts.

Reference

Benedikt, Harry. New Jersey Institute Of Technology. http://www-ec.njit.edu/-hxb5327/harry3.html), Eyes and Vision, July 11, 2000

Matthews, Robert W., Matthews, Janice R., “Insect Behavior;” Robert E. Kreiger Publishing Company, Malabar, Fl. 1988

Title: Efficacy of two types of light traps in attracting insect pests of economic importance.
Personal Authors: Shashidhar Viraktamath, Kumar, K. H. D.
Author Affiliation: Department of Agril. Entomology, University of Agricultural Sciences, Dharwad - 580 005, India.
Editors: No editors
Document Title: Insect Environment
Abstract:

An experiment was conducted to evaluate the efficacy of Fine (India) light trap, which emitted bluish light, and ICRISAT-modified light trap, which emitted white light, in monitoring insect pests in agricultural and horticultural ecosystems at Dharwad, Karnataka, India. Daily collections were made during 08.00 h. Dichlorvos was used to kill the trapped insects which was replenished at weekly intervals. Both traps were equally efficient in attracting moths of Earias insulana, E. vittella, Mythimna separata, Thysanoplusia orichalcea, Spodoptera litura, Chilo partellus, Leucinodes orbonalis and Maruca testulalis [Maruca vitrata]. Fine trap was more efficient in attracting moths of Helicoverpa armigera, T. signata, Anomala spp. and Holotrichia serrata than the ICRISAT-modified light trap, this may be due to the blue light produced by the Fine trap.

Publisher: Navbharath Enterprises