杏吧原创

Why did I find the peak of Mount Etna covered in ladybirds but devoid of other visible flora or fauna?

(Continued)

My own experience indicates that one of the explanations you gave previously (1 December 2007) is correct. At university, my summer job was as a forest lookout, sitting from June to August in a tower perched on a 2400-metre mountain top in south-east British Columbia, looking for fires. I had lots of time for observation.

During two of the summers I found that my outdoor relaxation was disturbed by biting ladybirds. On further investigation I discovered on both occasions a veritable sea of the creatures under a nearby flat rock. An area of around 30 centimetres square was seething with ladybirds, maybe three insects deep. They showed no inclination to fly away, and because there was no chance of migration or hilltopping [insects being transported on warm updrafts] having brought them there they must have been preparing to hibernate, though it was quite early in the year for this.

鈥淢y outdoor relaxation was disturbed by biting ladybirds. I discovered a veritable sea of the creatures under a nearby rock鈥�

Interestingly, each summer there were predictable swarming times for different insects. For example, over a three-day period, a flying ant infestation would build up and then die down. I assume ants have to keep assignations simple 鈥� such as 鈥渓et鈥檚 meet at the highest place鈥�. Although the lookout windows were covered with climbing ants, the radio antennas above were covered even more densely. This too was not a hilltopping or updraft event, because different species would arrive on different days and there was a build-up and a die-down over the three days.

David Shelton, British Columbia, Canada