Town-dwelling spiders are not afraid of the light

MOST SPIDERS avoid light because, besides being predators, they are also potential prey. But there is a set of circumstances in which living beside a powerful light is an advantage. This is when you are a web-weaving spider. Moths and other insects are attracted to sources of illumination such as streetlights. Those are found predominantly in cities. It would therefore make sense if urban web-spinning spiders had lost their photophobia, so that they could more easily set up shop beside such lights. And an experiment by Tomer Czaczkes of the University of Regensburg, in Germany, suggests that for at least one species this has happened.Dr Czaczkes’s interest in whether city life shapes spiders’ behaviour began when he saw lots of fat, happy arachnids building webs near Regensburg’s streetlamps. Delving into the academic literature, he discovered that urban moth populations have been shown to be less attracted to lights than are their rural relatives. Presumably, this is because, besides any webs involved, the whole business of flying round and round such lights is a fitness-reducing waste of time and energy. He reasoned that a similar but reverse sort of logic—resulting in their being more attracted to lights, or at least less afraid of them—should apply to town spiders versus country ones. And, as he reports this week in the , it does.