Abstract: 【Aim】 The geomagnetic field (GMF) is not constant and varies with space and time. To date, most studies related to the animal responses to magnetic field changes focus on magnetoreception during the magnetic orientation and navigation in migratory animals. However, it is still unclear how the changes in GMF intensity between the emigration and immigration regions of migratory animals affect the physiology and behavior of these animals. 【Methods】 The test insects of the brown planthopper, Nilaparvata lugens, a migratory species, were collected from the paddy fields of Jiangsu Academy of Agricultural Science. The wing-form differentiation, phototaxis and flight performance of N. lugens adults under near-zero magnetic field (NZMF) and GMF, were investigated by indoors simulating NZMF and GMF with Helmholtz coil systems. 【Results】 The results showed that compared to the GMF, the NZMF significantly enhanced the proportion of brachypterous male adults by 6.4% (P<0.05), while showed no significant effects on the proportion of brachypterous female adults (P>0.05). For macropterous females, the NZMF significantly increased the proportion of the 2-day-old adults that moved towards the light by 55% (P<0.05), while significantly decreased this proportion in the 4-day-old adults by 22% (P<0.05). Overall, the NZMF showed an age-dependent effect on the phototaxis of N. lugens, strengthening the phototaxis at the younger age and then weakening it at the older age. Similar effects were found in macropterous male adults, but no significant effects on the phototaxis of adults at a certain age were found (P>0.05). The NZMF significantly decreased the flight time of the 2-day-old macropterous male adults by 46% (P<0.05), and significantly increased the flight speed of macropterous female and male adults by 65% and 101% (P<0.05), respectively. In addition, the flight speed of macropterous male adults was significantly lower than that of macropterous female adults under the GMF (96%) (P<0.05), while no significant differences were found under the NZMF (P>0.05). 【Conclusion】 The results suggest that the NZMF can enhance the proportion of brachypterous individuals of N. lugens, with an age-dependent effect on the phototaxis of macropterous adult, strengthening the phototaxis at the younger age and then weakening it at the older age. Moreover, the NZMF can also change the flight strategy of macropterous individuals in a way that increases the flight speed and shortens the flight time at the same time without changing their flight distance.

Key words: Nilaparvata lugens; near-zero magnetic field, wing-form differentiation, phototaxis, flight performance