The influence of the atmospheric boundary layer on nocturnal layers of noctuids and other moths migrating over southern Britain

  • Curtis R WoodEmail author
  • Jason W Chapman
  • Donald R Reynolds
  • Janet F Barlow
  • Alan D Smith
  • Ian P Woiwod
Original Article


Insects migrating at high altitude over southern Britain have been continuously monitored by automatically operating, vertical-looking radars over a period of several years. During some occasions in the summer months, the migrants were observed to form well-defined layer concentrations, typically at heights of 200–400 m, in the stable night-time atmosphere. Under these conditions, insects are likely to have control over their vertical movements and are selecting flight heights that are favourable for long-range migration. We therefore investigated the factors influencing the formation of these insect layers by comparing radar measurements of the vertical distribution of insect density with meteorological profiles generated by the UK Meteorological Office’s (UKMO) Unified Model (UM). Radar-derived measurements of mass and displacement speed, along with data from Rothamsted Insect Survey light traps, provided information on the identity of the migrants. We present here three case studies where noctuid and pyralid moths contributed substantially to the observed layers. The major meteorological factors influencing the layer concentrations appeared to be: (a) the altitude of the warmest air, (b) heights corresponding to temperature preferences or thresholds for sustained migration and, (c) on nights when air temperatures are relatively high, wind-speed maxima associated with the nocturnal jet. Back-trajectories indicated that layer duration may have been determined by the distance to the coast. Overall, the unique combination of meteorological data from the UM and insect data from entomological radar described here show considerable promise for systematic studies of high-altitude insect layering.


Insect layering Nocturnal boundary layer Temperature inversion Noctuid moths Entomological radar 



We thank Pete Clark from the UK Met. Office’s Joint Centre for Mesoscale Meteorology for UM data, Helen Webster from the UK Met. Office’s Atmospheric Dispersion Group for back-trajectory analyses and Ann Edwards for obtaining the insect alignment results. This work was supported by the UK Biotechnology and Biological Sciences Research Council (BBSRC) grant BBS/S/L/2003/10273 and a UK Met. Office CASE studentship.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Curtis R Wood
    • 1
    • 2
    Email author
  • Jason W Chapman
    • 2
  • Donald R Reynolds
    • 3
  • Janet F Barlow
    • 1
  • Alan D Smith
    • 2
  • Ian P Woiwod
    • 2
  1. 1.Department of MeteorologyUniversity of ReadingReadingUK
  2. 2.Rothamsted Radar Entomology Unit, Plant and Invertebrate Ecology DivisionRothamsted ResearchHarpendenUK
  3. 3.Natural Resources InstituteUniversity of GreenwichChathamUK

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