Three methods for measuring the Earth's magnetic field intensity in Apis mellifera (Hymenoptera: Apidae) drone...

The presence of magnetite in the abdomen of Apis mellifera suggests a role in magnetic signal perception, aiding orientation and navigation. Reproduction occurs in drone congregation areas (DCA), which are spatially and temporally stable, appearing in spring-summer during regionally specific mating flight times (midday to evening), when Earth's magnetic field intensity (EMFI) often increases. This coincidence points to a possible link between magnetism and DCA location. We evaluated 3 EMFI measurement methods-2 mobile apps (Crowdmag, Phyphox) and a low-cost magnetometer-at 3 known DCA in Argentina. At each site, 80 georeferenced sampling points were arranged in a 6 m grid. EMFI was recorded daily during the morning and evening at 10 and 150 cm above the ground. Results showed moderate positive correlations between EMFI and geographic coordinates and height. A weak positive correlation was also detected between EMFI and time of the day. All methods detected EMFI variation, but the low-cost magnetometer gave the most consistent readings, supporting its value as an affordable, reliable tool for EMFI assessment in apicultural studies. Present findings provide a baseline for investigating methodologies to assess the potential role of EMFI affecting DCA formation and adult male honey bee orientation during mating flights, with potential applications in improving reproductive management of A. mellifera colonies.