Utilisation of Molinia caerulea Tussocks by Overwintering Beetles at Epping Forest 113
Tullgren funnel equipped with 20 Watt bulbs. Discs of fine mesh were sealed over the samples to
prohibit the escape of beetles.
After 10 days the lights were switched off and the core sections, now dry, re-weighed. Any change in
weight was assumed to be caused by drying and allowed calculation of a crude measure of water
content by % weight. All beetles collected from the sample tubes (70% I.M.S.) were counted and
identified to species level where possible.
Identification was achieved using Joy (1932). Nomenclature employed that of Pope (1977) except
for Pterostichus rhaeticus, only recently distinguished from P. nigrita (see Luff 1990). Trixagidae is
referred to as Throscidae by some authors.
Results
Physical data
Internal temperatures of all tussocks in site 2 and 3 were 4°C whilst external temperatures fluctuated
between 4 and 5 °C. The internal temperatures of site 1 were slightly higher (4-6 °C), as was the
external temperature at a constant 6°C
Mean tussock heights, volume estimates and % water contents by weight of cores for each site are
given in table 1. Both Anovar and the non parametric Kruskal - Wallis test indicated that there was
a strongly significant difference between the volume estimates (P0.05). This means that core volumes, a function
of tussock height and cross sectional area (of corer), do not differ significantly but that the size of
tussock which they represent docs. (Mean core volume =1238 cm3, mean % of tussock represented
by core = 12%, 6% and 7% for sites 1. 2 and 3).
Essex Naturalist (New Series) 17 (2000)