Surveys to discover the habitats of mosquito species (Diptera: Culicidae) are useful for understanding their distribution, seasonality activity patterns, ecological interactions and the risk they pose for disease transmission. Therefore, in this study, we conducted a 1 year survey of mosquito species and analysed the seasonality and daily rhythms of four species found in a forest fragment from Southern Brazil. Collections were performed during the morning, afternoon, and evening, from October 2012 to September 2013. The most abundant species were Psorophora ferox, Aedes crinifer and Coquillettidia venezuelensis. Ae. crinifer was collected during all seasons, exhibiting diurnal and nocturnal activity in all seasons, except summer. Cq. venezuelensis was collected only in spring and summer and was primarily nocturnal. Haemagogus leucocelaenus, which transmits the Yellow Fever virus, was collected in spring, summer, and autumn; this species was primarily diurnal and was more active in the afternoon. Ps. ferox was collected in spring, summer and autumn and was primarily diurnal. Despite the low abundance of mosquito species at our study site, we consider that the knowledge about Culicidae fauna was improved, mainly regarding their biology. We provide new data about mosquito species in a specific area in Southern Brazil, which was once known to record deaths of non-human primates, a phenomenon that may be directly related to the presence of wild yellow fever vector mosquitoes.