Delta green ground beetles sometimes remain motionless for hours at a stretch, although they are more active in wet years than in dry years  In 1989 an observer spotted ten delta green ground beetles in nine hours  in 1985 the same observer at the same location had counted 38 in about two hours
Because of their excellent camouflage, delta green ground beetles are almost impossible to see if they are not moving.
 This difference probably does not reflect a drop in the population of these rare beetles over this period, however, because 1985 was a wet year and 1989 was relatively dry