Settling behavior of the desert isopod Hemilepistus reaumuri in response to variation in soil moisture and other environmental cues

We report the results of three studies, one observational and two manipulat ive, that examine the settling behavior of isopods in response to soil mois ture and other cues. In a census of isopod settling patterns in twenty-five 5 x 10 m plots arranged on a 200 m(2) grid, isopods settled more densely i n plots with more successful old burrows from the previous season, and in p lots with more shrubs. Isopod settling was not correlated with soil moistur e at 10 and 30 cm depths. In a manipulative experiment carried out over two years, isopods settled more densely in 3 x 3 m outdoor pens that received 20 mm of supplemental water in February than in unwatered plots. In a secon d experiment, 50 mm of water was added to open plots, and two densities of artificial holes were added as well. Isopods settled more densely in plots with added water, and settled much more densely in plots with artificial ho les. Water did not significantly affect isopod survival or offspring weight . Unmanipulated plots with higher densities of settlers had higher burrow s urvival.