This paper describes an automated system for acoustically monitoring bumble bee arrivals and departures from nests. In the last two decades, ecological research has demonstrated a widespread decline of bumble bees (Bombus spp.). Given that bumble bees are one of the most ecologically and economically important groups of pollinators, it is a priority to develop tools for detecting changes in worker foraging rate as "real-time" indicators of colony health. To collect data for developing these tools, we constructed and deployed artificial domiciles for queens to naturally take as residence. A single microphone was placed inside each nest to record intra-colony acoustics, and the audio from these microphones was processed to automatically report arrivals to and departures from the nest by resident bees. The described system reports time of each arrival or departure along with other features (especially fundamental frequency), providing a foundation for ongoing improvements in remote monitoring that will yield greater insights into bumble bee behavior and colony development.