Geomagnetic Orientation And Mechanism Of Migration In Insects

The geomagnetic orientation is one of the most important orientation mechanisms for the long-term migratory insect pests. In this study, the key rice pest of brown planthopper, Nilarvata lugens, as being one typically long-distance migratory insect, was selected to detect the magnetic materials using Superconducting Quantum Magnetometers, and to ascertain its distribution in adults’body and identify the materials properties. The results indicated that the diction of magnetic materials using whole insect body was too poor. The inflexions of temperature-demagnetization curves, detected in the abdomen of the1st-5th instar nymphs, and macropterous and brachypterous adults of female and male N. lugens adults, were obviously found at T=220K, and hysteresis loops were also clearly closed for the diction of the abdomen of the1st-5th instar nymphs, and macropterous and brachypterous adults. So there were hysteresis (i.e., coercive force) and magnetic materials in the abdomen of N. lugens. While there were no the phenomenon of closed hysteresis loops detected in the cephalothorax of the1st-5th instar nymphs, and macropterous and brachypterous adults, showing no magnetic materials exiting in this body segment of N. lugens. Moreover, the magnetic materials were also directly observed in the abdomens of the1st-5th instar nymphs, and macropterous and brachypterous adults of female and male N. lugens using Optical Microscope (OM), Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM) after the Prussian Blue Staining. Furthermore, the magnetic materials were also identified as Fe3O4using EDX-analysis in combination with SEM. The existing of magnetic materials of Fe3O4in the abdomen provides substance basis for N. lugens using geomagnetic orientation during its long-term migration.We also set up directional flight simulated system which consists of tracking device unit, moving target’s tracking unit and virtual trajectory establishment unit was set up in this paper. This paper aims to achieve the function of insects’flying video acquisition and data processing, through the design and build of tracking platform, and the program of the software of moving target tracking and virtual trajectory establishment in the lab. The flight simulated system was used to begin the study on the migration situation and migration mechanisms of cotton bollworm and armyworm. The experimental environment including geomagnetic field, offset between the north and the south geomagnetic field and offset between the east and the west geomagnetic field. After data processing and analysis of many experimental videos, this paper preliminarily concluded that migration situation of cotton bollworm mainly concentrated between62°and106°(North direction as Y axis, East direction as X axis) and north and south geomagnetic field affected more than east and west geomagnetic field in the process of armyworm migration.The insect’s directional flight simulated system that designed and built in this paper exert the function of experimental videos acquisition, moving target tracking and virtual trajectory establishment, which offer the basis to the in-depth research on the insects’ migration mechanisms.