Mosquitoes are considered one of the more severe worldwide health hazards. Their populations vary heterogeneously in urban and rural landscapes, and fluctuate with seasonal or climatic trends and human activities. Thus, frequent widespread high-resolution surveillance of mosquitoes is essential for both understanding their complex ecology and behavior, and also predicting disease risk and formulating effective control strategies against mosquito-borne diseases such as malaria, dengue and Zika. To this end, in this paper, we present LOCOMOBIS, a LOw-COst MOsquito BIoacoustic Sensor where the wingbeat sounds produced by mosquitoes in flapping-wing flight are used to identify different species automatically. The sensor has been deployed and tested in a real field deployment and our results demonstrate the practical feasibility of this low-cost nonintrusive approach for monitoring mosquitoes in places requiring vector monitoring aimed at mosquito control or eradication. Moreover, to make the system more ubiquitous and easy to interact with, we implemented a web-based application where it is possible to check the collected data and the automatic species and gender classification.