The problem with zeroes: why don't drosophilids lay eggs?

We present some data on drosophilid oviposition and analyse the distribution of egg numbers over patches using an 'iterated' negative binomial. This suggests that there are three different reasons for empty patches; patches are not found, patches are not suitable, or females are not able to lay eggs. This leads to five categories of site which can be disentangled using the 'iterated' negative binomial. Since empty patches have important consequences for population dynamics and coexistence, this analysis will highlight how microscopic processes influence macroscopic behaviour in population biology.