Circadian rhythmicity allows organisms to adapt to regular day-night cycling and, importantly, to seasonal changes in their relative lengths. Recent experimental observations in the fly Drosophila have identified an additional class of neurons, the Evening-oscillators (E-cells) which when coupled with the well-characterized Morning-oscillators (M-cells) allow seasonal adapation to day length. Bulding upon our group's previously created mathematical model of the Drosophila circadian network in M-cells, we first study the gene network modifications necessary to create the experimentally observed behavior of the closely related E-cells. With a characterized E-cell gene network, we then stochastically simulate a small number of M- and E-cells to study the possible coupling mechanisms that yield the experimentally observed day length-dependent domination of one cell type over the other. This study will complement experimental efforts by providing both further insight into the possible mechanisms underlying the entrainment of circadian rhythms and the adaptation to widely varied seasonal changes in day length.