Return migration of Helicoverpa armigera (Lepidoptera: Noctuidae) during autumn in northern China

The autumn migration of Helicoverpa armigera (Hübner) was observed with radar and two types of light-trap at Langfang, Hebei province, China in 2001 and 2002. The sudden increase in the proportion of H. armigera moths in the searchlight trap indicated migration into the area and catches increased 10-fold during the second half of the night due to the landing of migrants before dawn. The moths' migratory flights took place at up to 2000 m above the ground, and moths flew differentially at times, and heights, when favourable (i.e. northerly) winds occurred. This facilitated the maximum displacement of moths towards the south during these 'return' migrations. The moths flew over the radar site at consistently high densities through the night, and the resulting flight durations of c. 10 h, at displacement speeds of 30-33 km h-1, would allow moths emerging in the far northeast of China (i.e. Liaoning and Jilin provinces and the Inner Mongolia autonomous region) to migrate into northern China (Hebei, Shandong and Henan provinces). The association of the seasonal migratory movements of H. armigera with crops in northern China is briefly discussed.     

Radar observations of the spring migration into northeastern China of the oriental armyworm moth, Mythimna separata, and other insects

Abstract. 1. The spring migration of the oriental armyworm moth, Mythimna separata (Walker), and other insects into northeastern China was observed by radar at a site in central Jilin province. Samples of the migrants were obtained in a net flown from a kite, and M.separata populations in the surrounding region were monitored with a trap network. 2. The radar regularly detected echoes which were of the type characteristic of large insects, and three out of four large insects in the aerial samples were noctuid moths, including one M.separata. Catches of armyworm moths in the regional trap network peaked during the period of radar observations. 3. Migration occurred at night. It commenced with a take-off flight at dusk and generally continued until dawn, with numbers often being highest around midnight. Most migration took place at altitudes below 500 m, with strong layer concentrations forming at 200–400 m during the middle part of some nights. 4. Migration was approximately downwind. The net movement was overwhelmingly to the northeast because southwesterly winds occurred most frequently and were relatively strong, and because migration was more intense and prolonged on these winds. Orientation tended to be to the left of the downwind direction, and was most often to the north or northeast. 5. Migration into northeastern China was accomplished in a series of night-time movements of 100–300 km rather than by a single non-stop flight. 6. The net movement of insects towards the northeast was sufficient to produce the observed regional infestation of M.separata moths. Oviposition by immigrant armyworm moths in vulnerable crops would have been at a level where economically significant damage would be expected from the resulting larval population. 7. Analogous springtime migrations of noctuids leading to temporary colonizations of habitats at higher latitudes occur in other continents. Such colonizations may be unproductive if, as appears possibly the case for northeastern China, prevailing winds later in the season are generally unfavourable for a return migration towards overwintering areas at lower latitudes.     

Autumn migration of Mythimna separata (Lepidoptera: Noctuidae) over the Bohai Sea in northern China

The autumn migration of Mythimna separata (Walker) (Lepidoptera: Noctuidae) across the Bohai Sea was observed with a scanning entomological radar and a searchlight trap at Beihuang, an island located in the center of the Bohai Gulf of northern China, in 2003-2006. During the autumn migration, M. separata flew at the altitudes of 50-500 m, with a displacement speed of 4-12 m/s, toward the southwest. Variations of area density of the radar targets and of catches in the searchlight trap through the night indicated that the flight duration of M. separata was approximately 10 h. Based on these observations, M. separata that originated in northeastern China (i.e., Liaoning, Jilin, and Heilongjiang provinces and part of the Inner Mongolia autonomous region) could immigrate into eastcentral China and subsequently to southern China (i.e., Fujian, Guangdong, and Guangxi provinces) within a week for overwintering.     

2010年牧区2代草地螟成虫迁飞的虫源分析

草地螟(Loxostege sticticalis L.)是危害我国北方农牧区的重要迁飞性害虫,明确其迁飞、扩散规律以及与境外虫源交流情况,对早期预警和有效防治具有重要意义。2010年6月1日至9月17日,利用垂直监测昆虫雷达的观测资料,结合探照灯和地面灯灯诱虫情、迁飞高峰期雌虫卵巢解剖、区域大气环流形势和迁飞轨迹分析,在内蒙古锡林浩特西郊研究了牧区2代草地螟的迁飞过程,结果表明:2010年牧区2代草地螟迁飞高峰期出现在2010年8月8日至8月21日,高峰日为8月11日,高峰日探照灯诱虫量达9167头,卵巢发育级别以1—2级为主,高峰日雷达回波主要集中在300—400 m。轨迹分析显示:迁飞高峰期8月8日、8月10—12日牧区草地螟迁飞虫源主要来自蒙古共和国东南部及中蒙边境地区,由蒙古气旋西南侧的西北气流输送进入我国内蒙古锡林郭勒盟,再随西南气流迁入呼伦贝尔草原。     

褐飞虱2009年秋季回迁的雷达监测及轨迹分析

褐飞虱Nilaparvata lugens (Stål)是水稻生产上重要的迁飞性害虫,研究其迁飞、扩散规律,为早期预警和有效防治提供科学依据。2009年4月27日至10月11日, 在中国农业科学院植物保护研究所重大病虫害监测预警兴安雷达站内利用毫米波扫描昆虫雷达对褐飞虱的迁飞过程进行长期观测,高空探照灯诱虫器及佳多自动虫情测报灯诱虫器分别用来诱捕高空及地面的褐飞虱,对高空探照灯诱到的褐飞虱雌成虫随机挑选30头进行卵巢解剖, 并结合大区环流和利用Hysplit_4模型进行轨迹分析,研究了褐飞虱的秋季回迁过程和虫源。结果表明：褐飞虱秋季回迁高峰期出现在9月28日至10月7日,高峰日为10月1日, 高峰日内雷达回波主要在600~1 100 m范围内聚集成层,高空探照灯诱虫器内褐飞虱的数量达到了13 620头;卵巢发育级别以1~2级为主。轨迹分析显示：本次回迁的褐飞虱主要来自湖南衡阳和永州等地,随东北气流向广西柳州、南宁和崇左等方向迁飞。轨迹推断与褐飞虱实发虫情基本吻合,通过毫米波扫描昆虫雷达确定了褐飞虱秋季回迁的高度,为毫米波扫描昆虫雷达早期投入到预测预报的实践中奠定了基础,对我国褐飞虱早期预警体系的建立将提供必要的技术支持。     

Nocturnal migration of dragonflies over the Bohai Sea in northern China

Abstract.  1. A sudden increase and subsequent sharp decrease of catches of dragonflies in a searchlight trap, with Pantala flavescens Fabricius (Odonata: Libellulidae) predominating, observed at Beihuang Island in the centre of the Bohai Gulf, in 2003 and 2004, indicated a seasonal migration of these insects over the sea during the night in China. The movements were associated with the onset of fog.
2. Simultaneous radar observations indicated that the nocturnally migrating dragonflies generally flew at altitudes of up to 1000 m above sea level, with high density concentrations at about 200–300 or 500 m; these concentrations were coincident with the temperature inversion.
3. During early summer, the dragonflies oriented in a downwind direction, so that the displacement direction varied between different altitudes. In contrast, during late summer, the dragonflies were able to compensate for wind drift, even headwind drift, so as to orient south-westward no matter how the wind changed, and thus the displacement direction was towards the south-west.
4. The duration of flight, estimated from the variation of area density derived from radar data and hourly catches in the searchlight trap through the night, was about 9–10 h. The displacement speed detected using radar was ≈5–11 m s⁻¹. Therefore, the dragonflies might migrate 150–400 km in a single flight.
5. The dragonflies were thought to originate in Jiangsu province and they migrated into north-east China to exploit the temporary environment of paddy fields in early summer. Their offspring probably migrated back south during late summer and autumn.     

东北地区粘虫的季节性迁飞行为(英文)

粘虫Mythimna separata是我国农业生产上的重要害虫, 为了明确其季节性迁飞行为参数, 本研究采用垂直监测昆虫雷达（vertical-looking radar, VLR）及相关辅助设备的长期自动观测, 结合基于GIS的大区环流和轨迹模拟, 调查分析了2005年东北地区粘虫季节性迁飞行为。结果表明： 粘虫在不同季节和夜间不同时间空中飞行高度具有明显差异, 空中飞行行为受气象条件尤其是空中风场影响较大; 春季和秋季主要借助气流运载进行大规模长距离迁飞, 夜间持续飞行时间可达9 h, 多数个体能完成整夜飞行, 春季迁飞高度主要在300~600 m, 秋季飞行高度相对较低主要在300 m以下和400~500 m。夏季雷达回波有明显的成层现象, 最高可达1 000 m, 主要集中在500 m和700 m两个高度层。轨迹分析显示： 5月29日由山东潍坊、 临沂等虫源地起飞的黏虫, 顺西南气流越海迁飞, 6月1日在气旋天气影响下, 在吉林省白城等地降落; 7月中旬主要为当地黏虫受对流天气影响进行短距离迁飞扩散; 9月11日虫源来自内蒙古呼伦贝尔, 顺西北气流向吉林省东南方向迁飞。研究结果为东北地区粘虫的有效防控提供了技术支撑。     

滇西南稻区白背飞虱种群特征及其关键影响因子

为明确滇西南沧源县稻区白背飞虱Sogatella furcifera的种群发生特征及其影响因子,于2010-2019年通过灯诱监测和田间调查的方法,分析沧源县白背飞虱的越冬种群、灯诱种群及田间种群发生特征,并对白背飞虱种群数量的影响因素进行相关性分析.结果表明:(1)白背飞虱以成、若虫在再生稻、落粒稻上越冬,越冬虫量最...     

华北二点委夜蛾种群动态监测及北京北部地区虫源性质分析

二点委夜蛾Proxenus lepigone是玉米生产中的一种新发害虫, 2011年曾在黄淮海夏玉米主产区全面暴发, 对夏玉米生产构成严重威胁。为了明确二点委夜蛾的种群动态, 探讨北京北部二点委夜蛾种群是否为迁入虫源, 2012年, 在华北地区的河北省栾城县、 北京市区和北京延庆县等地, 利用高空探照灯诱虫器、 垂直监测昆虫雷达等对二点委夜蛾成虫进行了监测, 并结合气象资料, 对北京延庆的虫源性质进行了综合分析。结果表明： 二点委夜蛾老熟幼虫作茧后可在北京延庆越冬。2012年, 北京延庆诱集二点委夜蛾累计33 951头, 可划分为3个世代。第1代成虫的诱集数量不符合正态分布, 且在姊妹灯下的数量差异符合迁飞种类的特点。在当地条件不适宜的情况下, 北京延庆监测点第1代成虫日均诱虫数量高于条件相对适宜的河北栾城。在北京延庆, 第1代成虫的逐日诱集数量与空中风向密切相关。雷达监测还表明二点委夜蛾可能是雷达回波的目标。综合以上证据表明, 北京延庆第1代成虫包含从周边迁飞而来的个体, 二点委夜蛾可能是一种兼性迁飞昆虫。本研究可为二点委夜蛾成虫能否远距离迁飞提供例证, 对今后提高其预测预报和防治水平具有重要意义。     

The long-distance migration of Nilaparvata lugens (Stål) (Delphacidae) in China: radar observations of mass return flight in the autumn

Abstract.

• 1 A case study is presented of the autumn migration of the brown planthopper, Nilaparvata lugens (Stål), in the area of Nanjing in the People's Republic of China. The study was made using a high frequency (8 mm wavelength) radar and a net suspended from a kytoon.
• 2 The observations confirmed that long-distance return migrations occur in China in mid and late September, with N.lugens being carried on the prevailing north-easterly wind towards the autumn infestation and overwintering areas of the species.
• 3 After mass take-off in the late afternoon or at dusk, the migrants flew for several hours during the evening, often in a dense layer which formed at heights between about 400 and 1000m above ground. These layers often had well-defined ceilings corresponding to an air temperature of about 16°C. The migration height was above the top of the surface temperature inversion, i.e. the migrants did not fly at the height of the warmest air.
• 4 The dense layer concentrations overflying the radar were backtracked to source areas up to 240 km away in the north-east of Jiangsu Province. Planthoppers observed emigrating from the Nanjing area would reach areas in south Anhui Province or north Jiangxi Province if they flew for 12 h.
• 5 There was a second period of mass take-off at dawn. Insect layers sometimes formed but did not last longer than 1–2h.
• 6 The present results were strikingly different from those previously observed in the dry season in the Philippines, where migratory flight durations were largely confined to periods of about 30min at dusk and dawn.
• 7 Our observations are discussed in relation to the equator-wards return migrations undertaken in autumn by other insect species, and the importance of these migrations for the maintenance of long-flying genotypes in the overwintering populations is considered.

     

Reproduction-flight relationship in the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae)

To evaluate the relationship between reproduction and migratory flight, we examined ovaries, tethered flight, and egg laying in the beet armyworm, Spodoptera exigua (Hübner). Ovarian development in female S. exigua was classified into five stages in relation to the postemergence age of the moths. Oviposition peaked at ovarian stages III and IV. Mating accelerated ovarian development in this species, and thus the mated females developed faster than the virgin moths in ovaries. In virgin adults, flight capacity increased from the first day to the third day after emergence and remained at a high level until the moths were 7 d old. In contrast, the mated moths reached the maximum flight capacity in 2 d after emergence and maintained a high level until the age of 7 d. However, mating status could not influence the flight capacity of the beet armyworm, although there were general differences in flight capacity between virgin and mated adults at the same age. Moreover, significant correlations between the number of eggs laid and the flight capacity were not performed by the mated moths. These results showed that mating status and ovarian development did not seem to influence flight capacity in the beet armyworm, which was not in agreement with the definitions of the oogenesis-flight syndrome observed in many other migratory insects.     

Nocturnal passerine migration without tailwind assistance

Nocturnal passerine migrants could substantially reduce the amount of energy spent per distance covered if they fly with tailwind assistance and thus achieve ground speeds that exceed their airspeeds (the birds’ speed in relation to the surrounding air). We analysed tracking radar data from two study sites in southern and northern Scandinavia and show that nocturnally migrating passerines, during both spring and autumn migration, regularly travelled without tailwind assistance. Average ground and airspeeds of the birds were strikingly similar for all seasonal and site‐specific samples, demonstrating that winds had little overall influence on the birds’ resulting travel speeds. Distributions of wind effects, measured as (1) the difference between ground and airspeed and (2) the tail/headwind component along the birds’ direction of travel, showed peaks close to a zero wind effect, indicating that the migratory flights often occurred irrespective of wind direction. An assessment of prevailing wind speeds at the birds’ mean altitude indicated a preference for lower wind speeds, with flights often taking place in moderate winds of 3–10 m/s. The limited frequency of wind‐assisted flights among the nocturnal passerine migrants studied is surprising and in clear contrast to the strong selectivity of tailwinds exhibited by some other bird groups. Relatively high costs of waiting for favourable winds, rather low probabilities of occurrence of tailwind conditions and a need to use a large proportion of nights for flying are probably among the factors that explain the lack of a distinct preference for wind‐assisted flights among nocturnal passerine migrants.     

草地螟2007年越冬代成虫迁飞行为研究与虫源分析

草地螟 Loxostege sticticalis L.是危害我国北方农牧业的一种重要迁飞性害虫,明确草地螟的虫源地及迁飞路线对其早期预警具有重要意义。本文利用垂直监测昆虫雷达的长期观测,迁飞高峰期雌虫卵巢解剖、大区环流分析、各地虫情信息收集和利用Hysplit_4模型进行轨迹分析,研究了2007年越冬代草地螟的空中迁飞行为和东北地区严重暴发的草地螟虫源。结果表明：6月7–9日,雷达观测点诱虫灯内草地螟具有典型迁飞昆虫生理特征;草地螟主要在夜间迁飞,飞行高度集中在300～500 m,400 m是主要飞行高度,迁飞高峰期夜间迁移可持续9 h。东北地区严重发生的草地螟虫源,一部分来自内蒙古乌盟地区,一部分来自蒙古共和国中东部及中俄边境地区。据此推测我国与国外草地螟存在虫源交流。     

Does the onset of sexual maturation terminate the expression of migratory behaviour in moths? A study of the oriental armyworm, Mythimna separata

It is generally accepted that in most insects adults are sexually immature when they initiate migration and that migratory behaviour terminates with the onset of sexual maturation. However, a few studies examining the mating status of field collected moths have suggested that sexually mature individuals may continue migrating, but in these cases it was impossible to completely eliminate the possibility that the mated females captured came from local, non-migrant populations. In this study we examined the ovarian development of Mythimna separata females captured using a vertical pointing searchlight trap on Beihuang Island in the Bohai Gulf, China, a site >40 km from land. Moths were collected from May to October from 2003 to 2008 in order to test the hypothesis that the onset of sexual maturation resulted in the termination of migratory behaviour. While females at the end of the summer had little ovarian development and were unmated, a significant proportion of those migrating northward in the early summer had developed ovaries and often had at least one spermatophore. Given that theses insects were captured while flying up to 500 m above sea level, at a site with no local populations, the findings would not support the hypothesis and suggest that both ovarian development and mating may occur during migration.     

Effects of Transgenic Petunia Expressing Bacillus thuringiensis Toxin on Selected Lepidopteran Pests

Toxicity of 11 transgenic petunia lines expressing the CryIA (c) insecticidal crystal protein of Bacillus thuringiensis subsp . kurstaki was investigated using lepidopteran neonates Spodoptera exigua, Trichoplusia ni and Manduca sexta. Mortality of S. exigua, T. ni and M. sexta varied within and among transgenic petunia lines . Bioassay results demonstrated that levels of CryIA (c) expression obtained in 7 out of the 11 transgenic petunia lines produced at least 50% mortality in S. exigua and T. ni, and all 11 transgenic lines produced more than 80% mortality in M. sexta. Demographic analysis of the biological impact of transgenic petunia on S. exigua revealed that sub - lethal feeding on transgenic petunia significantly reduced larval weight and prolonged larval and pupal development times . Continuous feeding on transgenic petunia significantly reduced lifetime fecundity , egg hatch and longevity in female and male moths . Compared with insects fed continuously on non - transgenic petunia , lifetime fecundity and net reproductive rate were reduced by 58 and 84% in insects fed continuously on transgenic petunia respectively . Mean generation time was 8 days longer for insects fed continuously on transgenic petunia than for insects fed on non - transgenic petunia . Ovipositional attractiveness of transgenic petunia to S. exigua with respect to non - transgenic tomato or lettuce plants was similar , suggesting that petunia / tomato and petunia / lettuce may not be effective trap - cropping combinations . The potential and implications of using transgenic petunia as trap plants interplanted with crop plants for management of lepidopteran pests in the field are discussed .     

High-Altitude Windborne Transport of <Emphasis Type="BoldItalic">Helicoverpa armigera</Emphasis> (Lepidoptera: Noctuidae) in Mid-Summer in Northern China

The high-altitude windborne transport of the second-generation moths of Helicoverpa armigera (Hübner) was observed with radar in July 2001 and 2002 at Langfang, Hebei province, China. Moths of local populations took off at dusk, with area density peaking ca. 0.5 h later. The variation of area density through the night suggested that the maximum flight duration was about 8.5 h. The moths generally ascended to altitudes of up to 1500 m above ground level (AGL) and formed layer concentrations at ca. 300, 500, and 1000 m AGL. Multiple layering was very common and layers were located at zones of maxima in wind speed or in wind shear rather than in temperature inversions. Both the displacement direction and the orientation of the insect were at an acute angle to the downwind direction, rather than being distributed at random, and varied as the wind direction changed. The windborne moths were mainly transported into northeastern China where maize at the silking stage would have provided good hosts for the subsequent (third) generation of H. armigera. These population movements may account for the nondevelopment of resistance to Bt cotton in H. armigera in northern China.     

Radar observations of moths migrating in a nocturnal low-level jet

Abstract. 1. Radar observations of insects migrating at night over central-western New South Wales have detected an instance of migration in a low-level wind jet.
2. From the characteristics of the radar echoes, and from the catches obtained in traps at ground level and at the altitude of migration, the migrants can be identified as noctuid and pyralid moths of a number of different species.
3. The migration, which was in a downwind direction, started at dusk and ended at about dawn. During the period immediately before first light, a large proportion of the migrants were concentrated into a 100m deep layer at an altitude of about 250m; this layer had not been present during the first half of the night.
4. The boundary layer wind profile at dawn exhibited a clear low-level jet structure, with a wind maximum between 100 and 300m, and strong shear in the wind direction below 300m. A strong surface temperature inversion, but not a wind-speed maximum, had been present the previous evening.
5. The formation of the layer concentration in the upper part of the jet may be accounted for in terms of previously described responses of nocturnally migrating insects to a surface temperature inversion. It is not therefore necessary to assume that the migrants were responding specifically to the presence of a wind-speed maximum.     

Atmospheric trajectories and spring bird migration across the Gulf of Mexico

We examined the relationship between the longitude of peak arrival of trans-Gulf migrants on the northern coast of the Gulf of Mexico in spring and wind trajectories over the Gulf at three different altitudes (500, 1,500, and 2,500 m above ground level). We used data from 10 WSR-88D radars (weather surveillance radar-1988-Doppler) from Brownsville, Texas, to Key West, Florida, to record the time and longitude of peak arrival on the northern Gulf coast for four spring migrations (2001–2004). We used the National Oceanic Atmospheric Administration Air Resources Laboratory HYSPLIT transport and dispersion model at the READY Web site to generate backward, 24-h atmospheric trajectories based on archived atmospheric data for each trans-Gulf flight. The trajectories began at the geographic location where radar indicated the greatest concentrations of arriving migrants. Although the longitude of peak arrival varied, peak densities of most trans-Gulf migrants arrived on the northern coast near longitude 95°W. Regression analyses showed that the relationship between the longitude of peak trans-Gulf arrival and the direction of atmospheric trajectory was significant but weak at the 500-m level, where few migrants occurred, and was insignificant for the 1,500- and 2,500-m altitudes, where migrant densities were greater. We conclude that winds aloft over the Gulf have little influence on the longitude of peak trans-Gulf arrival on the northern coast of the Gulf of Mexico, and we speculate that the arrival pattern may reflect the trans-Gulf migration pathways that evolved during the Last Glacial Maximum.     

Mating disruption in Agrotis segetum monitored by harmonic radar

The long-range, pheromone-mediated, flight behaviour of male moths under natural and mating disruption conditions was monitored by means of harmonic radar. Individual male turnip moths, Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae), tagged with radar transponders, were released and tracked in plots with or without disruptive doses of sex pheromone. In addition, male attraction to pheromone-baited traps and mating of calling females in treated and untreated plots was investigated. High doses of a four-component pheromone blend reduced trap catch by 79% and mating of females by 62% when compared with control plots in pre-radar experiments. Surprisingly, this effect was not associated with any pronounced differences in flight behaviour of males between a treatment and a control plot as revealed by harmonic radar recordings. In total, 20 flight tracks from a control plot and 22 flight tracks from a treatment plot were analysed. Moths could be followed for up to 77 min, corresponding to a track length of 7350 m. Mean ground speed ranged from 0.7 m s^–1 to 5.4 m s^–1. There was a strong trend (P = 0.06) for a greater number of male orientations to traps from downwind in the control field compared to the treatment field. Many flight tracks were fragmented due to radar shadow. Advantages and constraints using harmonic radar to study the pheromone-mediated flight behaviour of nocturnal moths are discussed.     

Is Mythimna turca (Lepidoptera: Noctuidae) a migrant?

The double line moth, Mythimna turca (Linnaeus, 1761) (Lepidoptera: Noctuidae), is an important widely distributed insect species. Studies on the moth in European countries have focused on population monitoring and in China on taxonomy of Mythimna and distribution surveys of M. turca. However, whether M. turca is a migratory insect is unknown. Here, migration of the moth population was monitored using a searchlight trap from 2004 to 2020 on Beihuang island, Northern China, providing direct evidence that M. turca migrates across the Bohai Strait seasonally, in late May to early September. Population dynamics, ovarian development, wind direction and possible migration trajectories were also analyzed. Most moths migrated in June and at the end of August and the beginning of September, and a few migrated in May, July and October. The average duration of this windborne migratory period of M. turca was 93 d. Migratory trajectories demonstrated that M. turca mainly moved northward in spells of southerly winds from June to August and moved southward in spells of northerly winds during September. This new key information about the ecology of M. turca population will aid the formulation of M. turca management strategies.