iLAM: imaging Locomotor Activity Monitor for circadian phenotyping of large-bodied flying insects

Practical ToolsO_LIHistorically, most insect chronoecological research has used direct observations, cameras, or infrared beam-based monitors to quantify movement across timed intervals. Although some alternative DIY systems are cheaper than the current standard locomotor activity monitor, these options remain complicated to build and/or computationally intensive. C_LIO_LIWe developed the imaging Locomotor Activity Monitor (iLAM), an affordable ([~] $75 USD/unit) system for activity quantification. The iLAM utilizes a Raspberry Pi Zero W computer and night-vision camera inside a flight cage to photograph a population of insects at user-defined intervals. Open-source, modular R-scripts process the images and output a file containing the number, size, coordinate location, and timing for all movements (blobs) identified between consecutive images. Output can be analyzed directly or converted into the standard TriKinetics DAM format. C_LIO_LIWe demonstrated the flexibility and power of the iLAM system by comparing diel and circadian activity of different insect species (fireflies: Photinus marginellus, P. greeni, P. obscurellus), ecotypes (moths: Ostrinia nubilalis), and sexes (moths: O. nubilalis). Data captured by only six iLAMs ($450) identified that peak activity of O. nubilalis females (AZT: 19.2 hr) occurs significantly earlier than males (22.0 hr). Additionally, male moths from a univoltine population exhibited a significantly shorter endogenous period length (AZT: 21.3 hr) than males from a bivoltine genetic background (22.6 hr). C_LIO_LIThe iLAM will serve as a valuable tool for future researchers seeking to measure locomotor activity across diverse species, sexes, and populations in constant and changing environments. C_LI