I was walking the dogs this morning and we came across an interesting sight. There were huge numbers of woodlice marching down a hill in a continuous and steady stream. I have never seen this before and so we ditched our plans to have a long walk through the campo so that I could return home to grab my camera and record the spectacle.

I was curious as to whether this swarming behaviour has been seen before and when I looked into it I uncovered only one account of a lot of woodlice moving around at night in a large swarm and so seems that the dogs and I were seeing something quite unusual.

In the process of finding out about any swarming behaviour I was reminded of a few interesting things about woodlice and so, whether you want me to or not, I will share them with you. If you remember these kind of things you will be the life and soul of the next dinner party you attend. Here we go:

  • Like other arthropods woodlice need to shed their exoskeletons to grow but, for reasons best known to themselves, they do this in two stages shedding the rear half first and then two or three days later they shed the front half.
  • The “first” woodlice were marine isopod crustaceans that are thought to have colonised land during the carboniferous period so they have a pretty impressive track record having long predated the dinosaurs. Interestingly enough there were more than 800 kinds of cockroaches crawling around during the carboniferous.
  • There are shedloads of common names for woodlice and Wikipedia lists 35 which are limited to the English speaking world. No doubt there are many others. When I taught in New Zealand they were called slaters (as they are in Australia, Scotland and Northern Ireland). My favourite names form those given are Armadillo bug, Piggy Wig and Roly Poly. I believe John Humphreys tied an imitation for his trout in Pennsylvania and referred to them as Sow Bugs.
  • My hens which happily chow down on just about anything vaguely organic DO NOT like eating woodlice. I captured a sample from the swarm today with a view to giving the hens and exciting moving breakfast but they were less than keen. Apparently woodlice do not taste good. They are said to taste of “strong urine” (I am not going to conduct the experiment to verify this claim but you are welcome to do so in the interest of science. I would go as far as to say it is your duty to help illuminate the dark corners in our undersatnding. Let me know how you get on!). My sister Margaret tells me that her dog Tavi eats ants and other insects but won´t touch woodlice.
  • Woodlice have been observed to move in large swarms in the campo of Andalucía by the brilliant naturalist and philosopher Paul Hogan. Reasons for this swarming behaviour are currently unknown to science. Hogan himself suggests that maybe they just feel like it.

Here is some film of our little friends in action