Fig. 2. Leaving behavior. (A) Leaving frequency of the wild type and two eat mutants, eat-2 and eat-5, in a population leaving assay (eat-5 was tested on E. coli foods only). Worms were placed near the small chunk of bacteria and allowed to enter it; the time when the first worm entered the colony was time 0. The plot shows mean leaving frequency between 1 and 2 h after the start. On poor quality food, leaving is more active, and leaving behavior of eat-2 and eat-5 is more active than that of the wild type. Values are means ± s.e.m. (N=8). ^*Different from the wild type on the same bacteria (P<0.05). Different from P(leaving) of the same worm strain on good food, HB101 and Comamonas (P<0.05). All comparisons are by Student's t-test. (B) Leaving behavior of five individual eat-2 worms on E. coli DA837. A late-stage egg was placed near the colony. Time 0 is when the hatched larva first entered the colony. On the y-axis, `in' is the time spent in the bacterial colony, while `out' is the time spent outside the colony. (C) Leaving behavior of five individual wild-type worms on Bacillus megaterium; procedure as in B. Three out of five worms at some point, marked with arrows, left the colony and never returned. (D) Sample leaving trajectories of an individual wild-type worm on B. megaterium. Five typical segments of the animal's trajectory are shown with different colors, and the direction of movement is shown with arrows.