【作者】 高月波；

【导师】 翟保平；

【作者基本信息】 南京农业大学 ， 农业昆虫与害虫防治， 2011， 博士

【摘要】 许多昆虫利用远距离迁飞使自身从时间和空间上躲避不良环境并选择新的生境进行定殖。迁飞性昆虫选择空中乘风飞行,飞行高度通常距离地面几百米以上,昆虫可以借助高空的高风速实现更远的迁飞距离。许多迁飞性昆虫是非常重要的农业害虫种类,一些天敌昆虫也具有迁飞的习性。因此,深入研究昆虫迁飞行为对于调整和完善害虫的防治策略具有重要的意义。昆虫雷达技术的发展使直接监测空中虫群活动成为可能,雷达揭示了许多耐人寻味的空中虫群飞行行为现象,其中最为引人注目的便是聚集成层和共同定向现象。聚集成层和共同定向都可能导致害虫在相对狭小的区域内降落,进而导致严重的农业损失。本研究的目的就是要揭示空中迁飞虫群的飞行行为机制,以便为迁飞性害虫的异地预测提供科学依据。本研究通过室内模拟行为学试验、雷达观测、空中网捕、气象要素及轨迹分析等方法进行空中虫群飞行行为进行研究。在揭示空中虫群的飞行行为机制方面取得了进展。本文第一部分主要介绍借助自行设计的试验装置在室内模拟条件下对空中虫群的聚集成层、共同定向机制及昆虫飞行振翅行为进行的相关研究。第二部分重点介绍利用昆虫雷达监测和空中网捕等技术对昆虫迁飞进行野外观测和取样调查,进而分析空中虫群的飞行行为机制和迁飞动态。主要研究结果如下：1.为了揭示空中虫群的聚集成层行为机制,在模拟温度场和风场条件下对鳞翅目蛾类棉铃虫的飞行行为进行研究。在模拟温度场中,试虫群体表现为对温度的主动选择行为,其选择的两个敏感温度分别是最优飞行温度(20-22℃)和持续飞行低温阈值温度(13℃)。在模拟风场试验中,高速气流对试虫具有明显的吸附效应,其原因是在高速气流周围产生的负压引起向内的垂直气流运动迫使试虫加速进入并束缚在高速水平气流控制范围内。因此提出空中迁飞昆虫对最优飞行温度的主动选择使其趋向于逆温层顶的最高温处,而使空中虫群在位于逆温层顶的低空急流中聚集成层并长时间维持的关键因子是急流上下边缘处负压所形成的气流向心垂直运动。当环境温度显著低于迁飞昆虫的最优飞行温度时,昆虫会选择一直向上爬升直至其持续飞行低温阈值所在高度,从而形成温障层(Ceiling layer)2.为了明确风和磁场变化对昆虫定向飞行行为的影响,在模拟风场和磁场条件下对鳞翅目蛾类粘虫和棉铃虫的定向行为进行了研究。悬吊的蛾子在不同风速条件下均表现为逆风头向；在高速平流条件下释放时,多数蛾子仍表现为逆风头向振翅飞行。试虫对侧面风的补偿角度随风速的增大而减小,在无定向信号时,试虫群体的定向分布于风两侧；只有在试虫体侧设置明显点光源时,供试群体才表现出偏向风同一侧的共同定向,因此风本身不是迁飞性昆虫定向的信号。磁场定向试验结果表明,试虫在正常地磁场条件下表现为显著的群体共同定向。其中,粘虫群体的共同定向是轴对称的。当将试虫置于较强的磁场条件下时,粘虫和棉铃虫供试个体的定向行为发生变化,群体共同定向行为消失。试虫的定向行为不受磁场水平分量极向变化的影响。因此推断,迁飞性昆虫可能利用磁场作为自身定向的罗盘信号,在这个过程中可能和鸟类一样利用了磁倾角。3.对影响棉铃虫振翅频率的关键因子进行研究发现：持续飞行时间,交配行为,温度及风速风向显著影响棉铃虫振翅频率。棉铃虫振翅频率在供试前3个小时内迅速下降,随后振翅频率进入平台期,3小时后再次迅速下降,这一动态与昆虫迁飞过程中的起飞、运行和降落三个阶段十分吻合；交配行为致使棉铃虫雌、雄虫振翅频率降低,但雄虫振翅频率在短时间内得以恢复,而雌虫则不能。试虫在19-23℃之间振翅频率最高,这一温度区间恰为棉铃虫最优飞行温度区间,适宜的温度是迁飞性昆虫长时间振翅飞行的关键。在逆风头向条件下,风速对试虫振翅频率影响不大；但在顺风条件下,试虫的振翅频率伴随风速的增大显著降低,当相对风速大于4m/s时,昆虫几乎无法振翅。4.2007和2009年利用南京农业大学多普勒昆虫监测雷达对稻纵卷叶螟的迁飞行为进行研究。雷达观测表明：稻纵卷叶螟主要选择黄昏时分起飞、黎明降落。其飞行高度通常在500m以下。空中虫群通常在100-500m高度范围内聚集成层,有时不同高度上会同时出现2个虫层。成层现象通常与最大风速(低空急流)密切相关而与温度无关。利用数值模拟的方法对风温场及迁飞动态进行分析发现,2007年浦口地区的第4代稻纵卷叶螟有4次明显的迁入、迁出过程。其迁飞动态受台风、副热带高压和江淮气旋的强烈影响；降落行为与下沉气流密切相关。5.2009年8月至9月,利用系留气艇携带高空捕虫网的方法对南京浦口地区的空中昆虫群落进行采样研究。结果表明：半翅目同翅亚目昆虫为网捕优势类群,其中稻飞虱、蚜虫及叶蝉等贡献最大；其次为双翅目和膜翅目昆虫。寄生蜂、捕食蝽等天敌昆虫与其寄主之间存在明显的伴迁行为。白天和夜间网捕在种类构成上存在明显的不同,不同的昆虫种类选择的飞行时间不同,蚜虫和寄生蜂等小型昆虫在白天比较活跃,而稻飞虱、叶蝉及鳞翅目成虫等在夜间迁飞。对整夜空中虫群的采样研究表明,傍晚时分捕获的昆虫数量与种类明显多于其他时段。空中网捕昆虫数量动态不同程度受到温度、风速和风向的影响。通过对几种重要稻飞虱种类的轨迹分析研究表明,网捕昆虫动态能够真实反映小型昆虫的实际迁飞动态。6.利用以往雷达观测数据对东北地区春季粘虫空中虫群的迁飞行为进行研究。结果表明：空中虫群的成层趋向于逆温层顶,选择较高的温度是空中虫群聚集成层的主要原因,但少数成层现象与风切变有关。低温是粘虫迁飞的重要限制因素,当温度低于13℃时粘虫很少起飞,空中虫群也不聚集成层。急剧降温会导致空中虫群的集中降落。空中虫群的位移方向的离散度与风速呈显著负相关。当风速较大(>5m/s)且风向为东北时,粘虫虫群的共同定向基本与风向一致；当风速较小(<3m/s)且风向与粘虫迁飞的意愿方向(东北)相差很大时,空中虫群表现为明显的侧风补偿甚至逆风飞行的行为。粘虫的共同定向与月亮无关,定向过程中可能利用了诸如地磁场等罗盘信号。更多还原

【Abstract】 Many insect species undertake regular seasonal migration in order to exploit suitable breeding habitats. Migratory insects engage in high-altitude, windborne migration, often at heights of several hundred meters above ground level, at where they can take advantage of strong wind to fly considerable distance. The atmospheric transport of insects is worthy of study because many migrant species are serious pests of agriculture while other insects are important natural enemies. Knowledge of insect movement is necessary when formulating or improving management strategies for the species concerned. The development and use of entomological radar has made it possible to direct observe the high-altitude movements of insects. Entomological radars have revealed many fascinating phenomena, but among the most noticeable phenomena are the layer formation and common orientation of aerial fauna. Both of two flight behavior can cause a greater concentration of migratory pests in the fallout area and heavy loss of agriculture production. The aim of this study is to reveal the behavioral mechanisms of aerial migratory fauna, focus on layer formation and common orientation of nocturnal insects, and the results will provide very useful information for the remote forecast of migratory insect pests.Simulation test, radar observation, aerial netting samples, analysis of meteorological factors and trajectory were used in this study. Some behavioral mechanisms of aerial migratory insects were explained satisfactorily. In the first part of this paper, the behavioral mechanisms of layer formation and common orientation were explored in simulation test by means of independent design experimental equipments. In the second part, the flight behavioral mechanisms and migration dynamics of Cnaphalocrocis medinalis, Mythimna separate and other small size insects were revealed by radar observations and aerial netting. The main results are as follows:1. The flight behavior of cotton bollworm Helicoverpa armigera was studied in simulated wind and temperature fields to explore the stratification mechanism of airborne migratory fauna. In the simulated temperature field, the tested moths exhibited significantly active selection behaviors for temperature. The moths tended to select their optimal flight temperature (20-22℃) and low temperature threshold (13℃) for flight. The result of simulation test indicated that high-speed airflow had significant suction effects on the tested moths, and that there was obvious negative pressure around the high-speed airflow. The inward vertical airflow generated by the high-speed removing jet pushed and bound the moths into the high-speed horizontal airflow. Our results illustrated that the active selection behavior of the airborne migrants for optimal flight temperature promoted their tendency towards the nocturnal inversion layer. The inward vertical airflow from the negative pressure at the edges of the low-level jet located on top of the inversion was the key factor that formed sustained layer concentration and aggregation of aerial fauna. If the environmental temperature was significantly lower than the optimal flight temperature of insects, the flying insects preferred to climb to their flight ceiling, i.e., the height with the low-temperature threshold.2. The orientation behavior of M. separate and H. armigera moth was studied in simulated wind and magnetic fields. Most of tether moths maintained upwind heading on condition of different wind speed and flew upwind when we released them in high speed horizontal airflow. The compensation angle for cross wind of moth decreased with increase of wind speed. The experimental moths exhibited common oriented to same side of airflow only when there was an obvious point light on the side of moths. Furthermore, we tested whether migratory moths orient by a magnetic compass in simulated magnetic field. Experimental moths exhibited common orientation in local geomagnetic filed and changed their heading obviously in the stronger magnetic field. The orientation behavior was not affected by polar change of horizontal component of magnetic field. Magnetic inclination may be the compass cues of aerial fauna collective orientation.3. The wing beat frequency (WBF) of H. armigera moths were tested in different conditions. The result showed that sustain flight time, temperature and mating behavior significantly affected WBF of moth. The WBF decreased quickly with the increase of sustain flight time in the first three hours, and kept constant over the next three hours, and then decreased quickly in the later period. This dynamic of WBF is a pretty good description of natural migratory dynamic of aerial fauna. The reducing of WBF of male moth caused by mating could be recovered in a short time, but female moth not. Moths maintained the maximum frequency and the longest time of wing beat when the temperature was between19and23℃. The wind speed had an obvious effect on WBF of moths in downward wind situation, nearly no efficacy on WBF in upward wind situation. Most of experimental moth could hardly beat double wings when the downward wind faster than4m/s. 4. Doppler insect monitoring radar observations of rice leaf roller Cnaphalocrocis medinalis migration were made at Pukou district of Nanjing in2007and2009. Radar observations showed that large numbers of rice leaf roller moths migrated from dusk (18:00h) until about05:00h the following morning and moths mainly flew below500m (agl). The majority of the migrating moths on any one night usually aggregated in layers between100m and500m (agl), and sometimes two moth layers were present simultaneously. The stratification of moth density was closely related to the low-level nocturnal jet rather than air temperature. We analyzed the migration dynamics and the temperature and wind profiles on the migration routes by numerical simulation. The results showed that there were four migrations of the4th generation of the moth in Jangpu2007. The rice leaf rollers engaged in southwards’return’migration on the northeast winds following the cyclone. Two massive immigration peaks of the rice leaf roller on the night of18-19and25August2007was associated with the subsidence around the low pressure system.5. Day and night sampling of windborne insects at a height of200m (agl) was undertaken at Jiangpu, Nanjing, from August to September2009, using a net supported by a tethered balloon. Hemiptera was the most frequent order in our catches on account of the abundance of the rice plant hopper, aphids and leafhopper. The abundance of Diptera was generally the second and Hymenoptera was the third. The accompanying migration of some natural enemies, e.g. parasitic wasp, with their host insects was found in the aerial netting studies. There was a significant difference in composition of species in aerial fauna between daytime and nighttime. Every insect species has a preferred time of flight. Aphids and parasitic wasp are active in daytime, but rice plant hopper, leafhopper and moths fly in nighttime. The insect population dynamics of aerial netting were affected by temperature, wind speed and wind direction. The trajectory analysis of the rice plant hopper indicated that the insect population dynamics of aerial netting can reflect the natural migration dynamics very well.6. The spring migration behavior of the oriental armyworm M. separate was studied based on the previous radar data. The results indicated that most moths trended to aggregate near the inversion upper surface in order to select warm condition. Only a few moths’ layers were related to wind shear. M. separate moths had a lower temperature threshold (about13℃) during the migration period. The mass landing of aerial fauna could be caused by sudden cooling. Furthermore, there was a significant correlation between the dispersion of migration direction for M. separate and the wind speed. When the wind was strong (>5m/s) and closely aligned with the armyworm moths heading (i.e., toward the NE), M. separate exhibited common orientation close to the downwind; When the wind speed wasn’t high (<3m/s) and not closely aligned with the moths heading, M. separate can compensate for the cross-wind drift and even flight upwind. The oriental armyworm M separate maybe use some compass cues (e.g., geomagnetic compass) to orient general flight direction.更多还原