Editing Swarm behaviour (section)

====Cockroaches====
[[Cockroach]]es leave chemical trails in their feces as well as emitting airborne [[pheromones]] for mating. Other cockroaches will follow these trails to discover sources of food and water, and also discover where other cockroaches are hiding. Thus, groups of cockroaches can exhibit [[Emergence#Living, biological systems|emergent behaviour]],<ref name="viegas">{{cite web |url=http://animal.discovery.com/news/briefs/20060327/cockroach.html |title=Cockroaches Make Group Decisions |publisher=[[Discovery Channel]] |author=Jennifer Viegas |access-date=10 June 2006 |url-status=dead |archive-url=https://web.archive.org/web/20080704111419/http://animal.discovery.com/news/briefs/20060327/cockroach.html |archive-date=4 July 2008}}</ref> in which group or swarm behaviour emerges from a simple set of individual interactions.

Cockroaches are mainly nocturnal and will run away when exposed to light. A study tested the hypothesis that cockroaches use just two pieces of information to decide where to go under those conditions: how dark it is and how many other cockroaches there are. The study conducted by José Halloy and colleagues at the [[Université Libre de Bruxelles|Free University of Brussels]] and other European institutions created a set of tiny [[robot]]s that appear to the roaches as other roaches and can thus alter the roaches' perception of [[critical mass (sociodynamics)|critical mass]]. The robots were also specially scented so that they would be accepted by the real roaches.<ref>{{cite magazine
|url=http://www.time.com/time/health/article/0,8599,1684427,00.html?imw=Y
|archive-url=https://web.archive.org/web/20071116222235/http://www.time.com/time/health/article/0,8599,1684427,00.html?imw=Y
|url-status=dead
|archive-date=November 16, 2007
|title=Robotic Roaches Do the Trick
|magazine=Time
|first=Michael D.
|last=Lemonick
|date=2007-11-15}}</ref>