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Generally stag beetles fly at dusk, when they are safer from predators. Males are seen in flight much more frequently than females. Why? It is known that they seem to prefer windless, and warm nights. Why? In fact one could go on asking questions about their flying habits; for instance, how fast and for how long can they fly? It would be nice to be able to answer some of these questions. Let's take each one separately and see what could be done. PS: End of season update, 4 September 2005 - It looks as if there are some answers to my questions, see below.
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| Q 1 | Why aren't females seen so frequently in flight? In the past I've only seen a few flying females. One as soon as it was released from mating in captivity, perhaps desperate to find a suitable egg-laying place. Another caught the attention of a blackbird during the during the day, fortunately landed unscathed on our lawn. András Andrási managed to take a picture of a female taking off. |
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| A 1 | I did see flying females, at least 6. From June 19, when there were mass flights over shrubs and large trees, the females took to the wing and I frequently saw them flying. However I just wished that I could have had a closer look at 12 other flying stag beetles, almost certainly females. Counted 63 flying males, so the flying female-to-male ratio was 0.1 : 1, much lower than the overall female-to-male ratio of the total monitored stag beetle population which was 0.4 : 1. | ||
| Q 2 | In which types of weather do they prefer to fly? It is known that their emergence is linked to the temperature [1], and also their activity [2]. But regarding their flying preferences I can only guess roughly because I happen to feel it in my bones. Not very scientific is it? Action - during the emergence season go out every evening, always at the same time, and monitor always the same area for flying stag beetles. At the same time find your nearest weather station, ideally a private one linked to Weather Underground, as the Met Office charges for their data. Weather Underground uploads the history as well as the forecasts. With the weather data, plus the flying nights, my husband might be able to create a program to find correlations. |
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| A 2 | I started monitoring the same patch, at dusk, from May 12 till July 6, 2005. The stag beetles emerged on May 25 and during that period there were 19 flying nights with a peak on June 17. I monitored a total of 191 stag beetles, a very healthy suburban population! David Fremlin writes about the weather correlation: "A crude analysis of the data suggests that beetles appeared more often when the temperature was relatively high and the humidity relatively low, and that these are acting to some degree independently, with the temperature being more important. For flying and mating beetles, the most important parameter remained temperature, but wind became relevant, perhaps as important as humidity." DHF 5 SEPTEMBER 2005. We are very grateful to Steve Tijou and Julian Best for their weather data without which this phenology study couldn't have been done. |
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| Q 3 | How fast do they fly? The only figure that I know of is 6 km/hr=1.7 m/sec [3], it would be nice to confirm it. Action - time beetles in short flights and at the same time mark their erratic flight path by dropping sand as you follow the beetle. A challenge, it involves going out in the evenings with a stopwatch, a notepad and a torch. Better with more than one person, I think.
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| A 3 |
Well I never got a chance to mark the path with lentils, Hansel and Gretel style, as was my intention, their flight was too erratic, just like in Lawrence Sail's poem. They lumbered, veered, zigzagged and tacked up the trees. I did however time some very short flights and got the following speeds for males only: 0.2 m/sec when flying very low; 0.4 m/sec slow cruising speed; 0.8 m/sec taking off. The speed of 1m/sec was recorded many times; just below 2 m/sec was the fastest speed measured but they can fly faster, I think.
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| Q 4 | How long do they fly? Action - time beetles in flight for as long as you can. As above, but much easier. Another way would be to attach a tether to the leg of a beetle and then wait for it to fly. Apparently this is a very old game still played by children throughout Europe till the last century. Did you know that the word for kite in French is cerf-volant? So, with patience, this could be tried with both male and female stag beetles.
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| A 4 | During the extraordinary June 17 2005 night when stag beetles were flying over some very tall trees everywhere, I did follow some individuals for well over 2 minutes until I lost sight of them. Soon after that I managed to have a tethered male flying for 6 minutes and 33 sec, which was really exciting, it did feel like flying a kite! The average speed was around 1 m/sec. | ||
| Q 5 | How far can they go? The only figure we have is 200 m taken between 4 hr readings of a male beetle with a monitor [4]. Action - follow a flying beetle for as long as possible or tag them. The latter is expensive, I'm afraid, no longer a case of rimby [research in my back yard].
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| A 5 |
All that I can say is that, several times, I observed fast flying beetles crossing the streets in no time at all, sometimes flying over 20 metres before I lost sight of them.
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Anybody who wants to try to have another go at any of these questions in the future is very welcome as it would be very nice to compare and pool the results. For more details just get in touch with me. |
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[1] - Findings of the 1998 National Stag Beetle Survey, PTES, pg. 21.
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