Glowing females were found throughout most of the site, in the churchyard East and North of the church (including in the steep verge on the Eastern side) and also in the parish cemetery (in smaller numbers). Most females displayed for one night only but many displayed several nights in a row, some for up to over 3 weeks. In total we estimate we recorded 59 different individual females in 2009, 160 in 2010 and 687 in 2011. In 2011 we started much earlier and saw the number of glowing females peak at 173 on 25 th June. In 20 we probably missed the height of the glowing season and therefore recorded modest numbers of glowing females with a maximum of 31 females in 2009 (17 th July) and 53 females in 2010 (23 rd June). In June-July volunteers walked throughout the site and recorded on a map all glowing females seen.
The survey was carried out at night in the summers of 2009, 20 in St Mary's churchyard and in the adjacent parish cemetery on Kingsclere Road. The light is a form of bioluminescence a molecule called luciferin is oxidised to produce oxyluciferin, and as it oxidises it produces the yellow-green glow that the glow-worms are famous for. Larvae can glow too, but with much fainter light and sometimes as pulsating light rather than as a continuous glow. Females usually display for two or three hours and if after that time they have not attracted a mate they stop glowing and retreat into the grass until the following night.
Females displays seem to be triggered by falling light intensity level.
Peak glowing time is June and July but can last from late May to September. Normally it is the virgin female beetle that glows and attracts males for mating. At night time they climb up grass stalks and glow while males fly around attracted to the characteristic glow. The female adult beetles also hide in the undergrowth during the day. They are nocturnal and are most active during moist conditions. Larvae live in sheltered places under rocks and wood, or hide in undergrowth during the day. They are rarely found on "improved" agricultural land. Glow-worms like chalky or limestone areas and prefer open grassland and hedges where snails and slugs are abundant.
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