Abstract:  The geomagnetic orientation is one of the important mechanisms for orientation of insects in the long distance migration. In this study, the long-winged and short-winged adults of the brown planthopper, Nilaparvata lugens, were selected to detect magnetic materials using Superconducting Quantum Interference Magnetometer (magnetic field range: ±4.8 mA/m; temperature range: 1.9-400 K) and to ascertain their distribution in the body. The results showed that there was no obvious turning point at T=220 K in temperature-demagnetization curve and no closed hysteresis loop in the whole body of long-winged male adults of N. lugens. Similar phenomena were found in long-winged female adults and short-winged male and female adults, suggesting that the detection of magnetic materials using whole insect body is not obvious. When tested using body segments, the turning points of temperature-demagnetization curves were obviously detected at T=220 K, and hysteresis loops were also clearly closed in the abdomen of long-winged and short-winged adults, suggesting that hysteresis (i.e., coercive force) or magnetic materials exist in the abdomen of N. lugens. In the meantime, there were no closed hysteresis loops detected in the cephalothorax of long-winged and short-winged adults, suggesting that no magnetic materials exist in this body part of N. lugens. The existence of magnetic materials in the body of N. lugens provides physical basis for its geomagnetic orientation during the long distance migration.

Key words: Nilaparvata lugens, wing morph, migration, geomagnetic orientation, magnetic materials