Environmental factors influencing daily foraging activity of <Emphasis Type="Italic">Vespula germanica</Emphasis> (Hymenoptera,Vespidae) in Mediterranean Australia |
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Authors: | M L Kasper A F Reeson D A Mackay A D Austin |
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Institution: | (1) Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, South Australia, Australia, 5005;(2) Biological Sciences, Flinders University of South Australia, Bedford Park, SA, 5042, Australia |
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Abstract: | In social insects, workers forego reproduction in favour of foraging and other tasks to promote growth of the whole colony.
Maximising individual work effort is limited by the physical constraints on foraging outside the nest. Previous studies of
factors influencing activity in social insects suggest that light intensity, ground and air temperature, relative humidity,
solar radiation, wind speed and/or rainfall may be important. This study aimed to determine which environmental factors influence
foraging in an invasive social insect, Vespula germanica, which has been introduced to Australia, where it experiences a hotter and drier climate than in its native range. Activity
was measured in terms of foraging traffic, with nests from a range of locations being monitored. Results indicate that the
onset of rain reduces activity by approximately 30%, but foraging returns to previous levels immediately after rain stops.
Foraging time is correlated with duration of daylight, with wasp daily activity being on average 22 min longer than the time
between sunrise and sunset. Low light was found to restrict wasp activity, as were low and high temperatures. A linear mixed-effects
model developed to explain the influence of these variables on numbers of foragers was highly significant. Under hot conditions,
V. germanica individuals thermoregulate their body temperature by regurgitating water. They also use water in evaporative cooling to keep
nests at optimum temperatures. Thus, in this species, hot temperatures increase the need for water, and so populations may
be severely impacted in seasonally hot regions where water is limited.
Received 30 March 2007; revised 10 March 2008; accepted 9 April 2008. |
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Keywords: | :" target="_blank">: European wasp German wasp Vespidae foraging weather |
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