Effects of Weather Conditions and Trap Types on Sampling for Richness and Abundance of Forest Macrolepidoptera

Abstract

In a 3-yr study (1991–1993), we compared blacklight and Townes-style Malaise traps for assessing richness and abundance of forest macrolepidoptera in 4 small watersheds in the Fernow Experimental Forest in West Virginia. From early May through mid-August each year, sampling was conducted by one 8-W blacklight trap and 5 Townes-type Malaise traps in each watershed. Light traps were operated 1 night each week; Malaise traps operated continuously with the samples collected every 10 d. Over all years, macrolepidopteran species richness and abundance were 343 and 36,160 and 273 and 28,246 for light trap and Malaise trap samples, respectively. Percentage of total macrolepidopteran species per family was similar in both collecting methods although both diurnal and nocturnal lepidopterans were represented in Malaise samples. Differences were noted in percentage of total abundance by family. For example, geometrid abundance was similar in both sample types and represented the highest overall abundance, whereas the proportion of arctiids and notodontids was higher in light trap samples, and proportional abundance of noctuids was higher in Malaise trap samples. There were 135 and 65 species unique to light trap and Malaise trap samples, respectively. Abundance of macrolepidopterans sampled by both methods was highest in 1991 (a warm, dry year) and lowest in 1992 (a cool, wet year). Minimum ambient temperature and rainfall significantly affected the sizes of samples from blacklight traps, based on multiple-regression analysis. Moonlight in the absence of cloud cover reduced moth catch in blacklight traps. Mean ambient temperature, but not total rainfall, during trapping periods significantly affected the sizes of Malaise-trap samples based on a multiple autoregression analysis.