Flight periodicity and the vertical distribution of high-altitude moth migration over southern Britain

Abstract

The continuous operation of insect-monitoring radars in the UK has permitted, for the first time, the characterization of various phenomena associated with high-altitude migration of large insects over this part of northern Europe. Previous studies have taken a case-study approach, concentrating on a small number of nights of particular interest. Here, combining data from two radars, and from an extensive suction- and light-trapping network, we have undertaken a more systematic, longer-term study of diel flight periodicity and vertical distribution of macro-insects in the atmosphere. Firstly, we identify general features of insect abundance and stratification, occurring during the 24-hour cycle, which emerge from four years' aggregated radar data for the summer months in southern Britain. These features include mass emigrations at dusk and, to a lesser extent, at dawn and daytime concentrations associated with thermal convection. We then focus our attention on the well-defined layers of large nocturnal migrants that form in the early evening, usually at heights of 200-500 m above ground. We present evidence from both radar and trap data that these nocturnal layers are composed mainly of noctuid moths, with species such as Noctua pronuba, Autographa gamma, Agrotis exclamationis, A. segetum, Xestia c-nigrum and Phlogophora meticulosa predominating.

Seasonal migration to high latitudes results in major reproductive benefits in an insect

“…Understanding the dynamics is also economically important, for A. gamma becomes a major pest of many African, Asian, and European crops during outbreak years (26). Just how representative A. gamma is of other migrant insects is a matter for future study, but given the similarities in the migration strategies of A. gamma to those of other insects in Europe (24,34), Asia (21), North America (3,5,19,20), and Australia (8,35), it is very likely that the results of the present study will be applicable to a wide range of migrants. We conjecture, therefore, that during a time when most sedentary Lepidoptera (36,37) and many migrant birds (38,39) have experienced dramatic declines, the shared traits of high fecundity (40), polyphagy (26), year-round breeding (26), reduced disease and parasite loads (41,42), and efficient strategies for the use of windborne transport (43) to exploit widely dispersed seasonal resources are the principal factors that have enabled the recent temperature-related range expansions and population increases observed in many species of migrant Lepidoptera (44).…”

“…Aerial netting at 200 m above the ground (22,24,47) and captures in 12-m-high suction traps (34) clearly demonstrate that macromoths are the only large (>50 mg) insects that are abundant, high-altitude, nocturnal migrants in the United Kingdom. We can thus be highly confident that the vast majority of VLR-detected large nocturnal insect targets were macromoths, and the aerial composition of this family in the United Kingdom is dominated by A. gamma (22-25, 34, 47).…”

Quantifying interspecific variation in dispersal ability of noctuid moths using an advanced tethered flight technique

“…1988) data on the occurrence of moths in traps 12.2 m above the ground over the period 2000–2009 (Wood et al. 2009). We used the presence of a study species in the top 25% of all species caught 12.2 m above the ground to infer a strong likelihood of the study species to engage in long distance dispersal (Wood et al.…”

“…We used the presence of a study species in the top 25% of all species caught 12.2 m above the ground to infer a strong likelihood of the study species to engage in long distance dispersal (Wood et al. 2009). …”

The peppered moth and industrial melanism: evolution of a natural selection case study

“…If the larvae enter the air stream, however, they could go much further (Liebert and Brakefield, 1987), the distance depending on how high they get. Studies using radar tracking show that British noctuid moths can be displaced 400 km or more in 8 h by prevailing winds (Wood et al, 2009;Chapman et al, 2010).…”