Across the genera of katydids from the family Tettigoniidae, both diurnal and nocturnal species have been identified. The Saint Louis Zoo Bayer Insectarium filmed dragon-headed katydids (Lesina blanchardi) overnight using red light-emitting diodes (LEDs) to examine the activity of this presumed nocturnal species to provide quantitative information about these insects that are otherwise immobile when keepers are present. Evidence from the literature suggests that LED bulbs emitting long-wavelength red and infrared lights are less likely to cause changes to the subjects' behavioral budgets and movements through the habitat. Three katydids were filmed for 5 nights, and time-interval scan sampling was used to record their positions and whether they were active every 15 min for two 2-h periods starting at midnight and noon. A modified Shannon's diversity index determined that katydids were recorded in more areas when under only red LEDs at night as compared to artificial daytime working lights. Similarly, repeated measures analysis of variance indicated that insects were significantly more active under nighttime red LEDs when compared to daytime working lights. While we cannot be sure if behaviors recorded under red LEDs are the same as those that would be performed under total darkness in situ, the use of red LED illumination ex situ to facilitate overnight filming did not suppress nocturnal movement or activity for our subjects.
Keywords: illumination; insect; nocturnal; photoperiod; wavelength.
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