Weather‐induced changes in moth activity bias measurement of long‐term population dynamics from light trap samples

Abstract

Interpretation of light trap catches of moths is complicated by daily variation in weather that alters flight activity and numbers caught. Light trap efficiency is also modified by wind and fog, and daily weather may effect absolute abundance (numbers actually present). However, actograph experiments and other sampling methods suggest that changes in daily activity are large by comparison to changes in absolute abundance. Daily variation in weather (other than wind and fog) is therefore a form of sampling error in absolute abundance estimates. We investigated the extent of this sampling bias in 26 years of population dynamics from 133 moth species. In a subset of 20 noctuid and geometrid species, daily numbers caught were positively correlated with temperature in 14 species, and negatively correlated with rainfall in 11 species. The strength of correlations varied between species, making it difficult to standardize catches to constant conditions. We overcame this by establishing how weather variation changed with time and duration of the flight period. Species flying later in the summer and for shorter periods experienced more variable temperatures, making sampling error greater for these species. Of the 133 moth species, those with shorter flight periods had greater population variability and more showed significant temporal density dependence. However, these effects were weak, which is encouraging because it suggests that population analyses of light trap data largely reflect factors other than sampling error.

Performance evaluation of locally developed black light trap for maize insects monitoring in Chitwan, Nepal

“…This result was similar to the result reported by Muirhead-Thomson (1991) that the BLTs had consistently caught a higher abundance and greater variety of insects during mid April to mid August than other traps. Similar results by (Mellanby, 1939;Holyoak, et al, 1997) showed that the higher insects were trapped from mid- May to the end of August. This may be because the higher temperature (Fig 5) increases flight activity and the numbers present in an area of both species and individuals.…”

Comparison of Sampling Techniques Used in Studying Lepidoptera Population Dynamics

“…We found the strongest relationship between moth abundance and the abundance of larvae collected from foliage in the species that were collected in the greatest abundance. Holyoak et al (1997) found that biased abundance estimates of moths collected by light traps were more likely in moth species with shorter ßight periods. Although pooled weekly abundance of moths collected in light traps may provide good estimates of annual abundance in well-represented species, less abundant species that are only present for a few weeks of the season may still be subjected to high sample error using this method.…”

Additive apportioning of lepidopteran and coleopteran species diversity across spatial and temporal scales in a cool–temperate deciduous forest in Japan

“…Holyoak et al (1997) demonstrated that the sampling efficiency of light traps depended on a series of meteorological conditions. Holyoak et al (1997) demonstrated that the sampling efficiency of light traps depended on a series of meteorological conditions.…”

“…Vertical stratification of diversity has been mainly addressed in Lepidoptera (e.g. In contrast, daily variations in diversity caused by weather are only reported for Lepidoptera collected in light traps ( Holyoak et al , 1997 ), but the variations may also be derived from differences in the dispersal ability or mobility of species. Odegaard, 2004;Charles & Bassett, 2005 ).…”