Abstract
Insects are one of the most diverse taxa and are fundamental to the delivery of many ecosystem services. Despite their global ubiquity and ecological importance, there is little research on temporal variation in insect activity, especially in the tropics where the group is most diverse. Gaps in our knowledge of insects are compounded by a lack of robust methods to monitor their activity at fine timescales. Ecoacoustic techniques have emerged as an effective means to monitor a range of taxa over long periods. Here, we assess insect acoustic activity in the eastern Brazilian Amazon across daily and seasonal cycles over 2 years. We relate acoustic indices to two subsets of manually assessed activity-sonotype diversity and spectrogram coverage. We find evidence for daily and seasonal periodicity, with both the spectrogram coverage and number of insect sonotypes higher nocturnally. Insect acoustic activity peaks during the dry season. Of the five acoustic indices used, the Bioacoustic Index best predicted acoustic insect activity across both metrics. Our results indicate that passive acoustic monitoring can be an effective tool for assessing broad trends in insect phenology.This article is part of the theme issue 'Acoustic monitoring for tropical ecology and conservation'.