library(ggplot2)
ggplot(mites, aes(x = WatrCont, y = pa)) + geom_point() + 
stat_smooth(method = "glm", family= "binomial", se = FALSE) + xlab("Water content") +
ylab("Probability of presence") + 
ggtitle("Probability of presence of Galumna sp. as a function of water content")