环境颜色对异色瓢虫生长发育及繁殖能力的影响

在室内利用不同颜色的饲养容器,对异色瓢虫Harmonia axyridis (Pallas) 生长发育、体长体重变化及繁殖能力进行了比较研究。结果显示：不同环境颜色条件对异色瓢虫幼虫各龄历期均有显著影响; 尽管蛹期受不同颜色影响显著,但其总胚后发育期在各处理间差异不显著。异色瓢虫1龄和2龄幼虫体长增量在不同颜色处理间无显著差异,但3龄幼虫在红色条件下体长增量显著小于其余各处理。不同环境颜色条件下异色瓢虫各虫期体重增量均有显著差异,而4龄幼虫体重增量在各处理中均显著大于其余各虫期,并占总胚后发育期体重增量的50%以上。异色瓢虫成虫的交配持续时间在各处理间无显著差异,但其产卵前期在黄色及绿色条件下显著小于其余各处理。其首堆产卵量在各处理间无显著差异,但在红色及自然光下的48 h累计产卵量均显著小于其余处理。     

异色瓢虫对枸杞木虱捕食功能及田间捕食效果

异色瓢虫Harmonia axyridis(Pallas)是枸杞木虱的优势天敌种类之一,为了明确不同龄期异色瓢虫对枸杞木虱4种虫态的捕食作用及田间控害效果,本文利用HollingⅡ型功能反应模型进行拟合以明确其捕食潜能,同时根据其捕食潜能的测算结果,在田间通过罩笼试验探究异色瓢虫4龄幼虫与成虫对枸杞木虱的捕食效果。结果表明:各龄期异色瓢虫幼虫对枸杞木虱4种虫态的捕食量存在显著差异,在枸杞木虱密度相同的条件下,异色瓢虫4龄幼虫的日捕食量最大,为92.9头;不同龄期异色瓢虫对枸杞木虱的捕食功能反应均符合HollingⅡ型方程,当枸杞木虱密度趋于无限大时,异色瓢虫4龄幼虫对枸杞木虱最大捕食量最大为411.5头;成虫对枸杞木虱的瞬间攻击率最大,为0.7931;4龄幼虫对枸杞木虱的处理时间最短为0.0051 d。田间释放异色瓢虫4龄幼虫与成虫的试验证明,处理植株上枸杞木虱虫口减退率,4龄幼虫为43.32%,成虫为14.78%;而对照组即周围8株植株上枸杞木虱虫口减退率,4龄幼虫为14.78%,成虫为16.22%;在异色瓢虫4龄幼虫释放区,处理植株上枸杞木虱虫口减退率为43.32%显著高于其周围8株植株的14.78%;而在成虫释放区,处理植株上枸杞木虱下降率为14.78%,对照组植株的虫口减退率为16.22%,没有显著差异。研究表明,异色瓢虫田间释放需根据枸杞木虱防治范围与力度的需求,选择适宜的异色瓢虫虫态进行枸杞木虱的生物防治。     

异色瓢虫非同胞间食卵自相残杀对成虫生殖力的影响

【目的】食卵自相残杀现象常见于瓢虫中,业已明确取食同胞卵对于初孵瓢虫至关重要,但取食非同胞卵的营养价值是否高于蚜虫仍存争议。本研究旨在明确异色瓢虫Harmonia axyridis在幼虫期除取食蚜虫外兼捕食非同胞卵是否影响其雌成虫的生殖表现。【方法】在异色瓢虫幼虫期设置3个饲喂处理,即仅饲喂禾谷缢管蚜Rhopalosiphum padi(对照)、除饲喂蚜虫外还分别给各龄幼虫饲喂少量非同胞卵(分散食卵)以及除饲喂蚜虫外仅给高龄幼虫饲喂较多非同胞卵(集中食卵)等,观察雌成虫体型大小、产卵前期、连续10 d的逐日产卵量和卵孵化率等形态和生殖特性。【结果】饲喂处理对瓢虫雌成虫体型大小无显著影响,对照、分散食卵和集中食卵3种饲喂处理下的雌成虫身体体积分别为92.30,89.73和93.98 mm~3;饲喂处理对雌成虫产卵前期也无显著影响,3种饲喂处理下雌成虫产卵前期分别为7.50,7.74和7.70 d;但饲喂处理对雌虫生殖力具有显著影响,分散食卵处理与对照无显著差异,羽化后10 d分散食卵和对照下累计产卵量分别为185和205粒,但集中食卵(88粒)比对照或分散食卵的产卵量显著降低;饲喂处理对卵孵化率无显著影响,对照、分散食卵和集中食卵3种饲喂处理下的卵孵化率分别为63.10%,72.58%和66.61%。【结论】结果说明,异色瓢虫各龄幼虫偶尔取食非同胞卵不影响其成虫的生长发育和生殖,但高龄幼虫捕食较多非同胞卵可降低其雌成虫的生殖力。     

不同龄期异色瓢虫对烟蚜的捕食潜能研究

异色瓢虫是烟田烟蚜的优势天敌种类之一,本文在室内进行了异色瓢虫成虫及各龄幼虫对烟草蚜虫的捕食功能反应试验,采用Holling-Ⅱ型功能反应模型进行拟合以明确其捕食潜能,利用Hassell模型和Watt模型拟合并测定了异色瓢虫种内干扰以及自身密度对烟蚜捕食作用的影响,结果表明:异色瓢虫各虫态对烟蚜的捕食量有明显的差异,在相同的烟蚜密度条件下,异色瓢虫4龄幼虫的日最大捕食量最大,为107.41头;其次是成虫,其日最大捕食量为94.34头;3龄幼虫、2龄幼虫和1龄幼虫的日最大捕食量分别为40.32头、14.25头和12.15头。在一定空间和相同比例猎物存在的条件下,种内干扰作用对1龄异色瓢虫幼虫的捕食量影响最为明显,干扰常数为1.1731,而对4龄幼虫干扰最小。各虫态自身密度对其捕食作用的干扰效应明显,1-4龄异色瓢虫幼虫以及成虫的竞争参数b值分别为0.5199、0.1848、0.1351、0.6757、0.6528。本研究表明异色瓢虫对烟蚜捕食潜力很大,尤其是4龄幼虫及成虫对烟蚜具有较大的捕食潜能。     

异色瓢虫不同光环境下的交配行为

光照条件是影响昆虫生长发育及生理行为变化的重要环境因子之一。以重要的捕食性天敌异色瓢虫为研究对象,借助动物行为自动观察系统对其在不同光照强度、光周期和光波长下的交配行为及繁殖力进行了分析研究。结果显示:(1)异色瓢虫的各交配行为和繁殖能力在有光和黑暗处理间具有显著差异;(2)异色瓢虫的求偶行为不受光照强度变化的影响,而交配持续时间及交配间隔时间在高光照强度下均显著短于低光照强度。尽管异色瓢虫的累积产卵量在不同光照强度间未见显著性差异,但是其幼虫孵化率随光照强度的增强显著降低;(3)异色瓢虫在光照时间较长的条件下表现出较高的交配求偶欲望,交配持续时间及交配间隔时间随光照时间的延长而缩短,其累积产卵量和幼虫孵化率均随光照时间的延长而显著增加;(4)不同环境颜色对异色瓢虫的求偶行为没有显著影响,但是其交配持续时间及交配间隔时间随照射光波长的增加而显著降低,雌虫的累积产卵量和幼虫孵化率均在黄色(575 nm)和绿色(510 nm)条件下最高,且显著大于其它处理。结果表明异色瓢虫的交配受光照条件影响极为显著,为进一步深入研究异色瓢虫环境适应性及提升其在生物防治中大规模饲养中的扩繁效率提供了重要的理论依据。     

使用生命表评价烯啶虫胺对异色瓢虫的影响

为正确评估广谱杀虫剂烯啶虫胺对天敌昆虫异色瓢虫Harmonia axyridis(Pallas)的影响,采取滤纸接触法测定了烯啶虫胺(防治蚜虫田间推荐用量)对异色瓢虫影响,并使用生命表研究了烯啶虫胺对异色瓢虫实验种群的影响,为协调害虫的化学防治与生物防治提供参考。结果表明:该剂量烯啶虫胺对异色瓢虫当代(F0)取食具有显著影响,药剂处理后7d内,成虫取食量显著降低;对F0代成虫寿命及雌虫繁殖能力未见负面影响;烯啶虫胺处理对异色瓢虫初产卵、F1代幼虫及蛹的历期没有显著影响;卵孵化率明显小于对照组,幼虫存活率及蛹羽化率没有显著影响。F0代种群净增值力、周限增长率、内禀增长率与对照相比差异不显著,分别为812.66粒(对照899.73粒)、1.084(对照1.093)、0.081(对照0.089),药剂处理种群加倍时间为8.557d,与对照7.888d相比没有显著延长。这些结果说明,大田中使用烯啶虫胺防治蚜虫时理论上对异色瓢虫种群繁殖及发育没有显著影响,但施药初期会影响异色瓢虫的取食量。     

转Cry1Ac/1Ab基因棉花对异色瓢虫生长发育及其捕食功能的影响

【目的】为探究转Cry1Ac/1Ab基因棉花对异色瓢虫生长发育及其捕食功能的影响。【方法】以转Cry1Ac/1Ab基因棉与其亲本常规棉为实验材料,利用取食不同棉花品种叶片的棉铃虫饲喂异色瓢虫幼虫。【结果】与常规亲本棉相比,取食饲喂转基因棉花叶片的初孵棉铃虫幼虫的异色瓢虫幼虫从1龄发育至化蛹期时间延长0.77 d,但差异不显著;除1龄幼虫体重增加(0.0773 mg)外,其余各龄期幼虫体重均有所下降,但差异均不显著;异色瓢虫1、2、3、4龄幼虫对初孵棉铃虫捕食量均随棉铃虫密度的增加而增加,捕食功能反应均符合HollingⅡ圆盘方程。【结论】转Cry1Ac/1Ab基因棉花对异色瓢虫生长发育无显著影响,饲喂取食转Cry1Ac/1Ab基因棉花的棉铃虫对异色瓢虫捕食功能无显著差异。     

异色瓢虫法国种群对豆蚜的捕食效应

异色瓢虫Harmonia axyridis(Pallas)的法国种群具有飞行能力较低的特点,在生物防治方面可能更具利用价值。为了使其更好的在田间应用,本文进行了异色瓢虫的法国种群各龄幼虫及雌、雄成虫对豆蚜的捕食功能比较研究。结果表明:各龄幼虫及雌、雄成虫对豆蚜捕食功能反应符合Holling II模型,检验各圆盘方程理论值和实测值拟合较好。同一虫态在不同空间水平对蚜虫的捕食能力有显著差异,在广口瓶处理中(较大空间),1～4龄幼虫及雌、雄成虫的最大理论捕食量分别为4.51、83.33、111.12、166.67、190及200头;不同虫期及成虫的瞬间攻击率a为3龄>4龄>雄虫>雌虫>2龄>1龄,且1龄的处理时间Th最长(0.2225);在培养皿处理中(较小空间),1～4龄幼虫及雌、雄成虫的最大理论捕食量分别为6.17、19.23、45.45、100、142.86、111.11头,不同虫期的瞬间攻击率a为2龄>3龄>雄虫>4龄>1龄>雌虫,且4龄的处理时间Th最长(0.1624)。     

保幼激素类似物苯氧威对异色瓢虫不同发育阶段的影响

【目的】本研究旨在明确保幼激素类似物苯氧威对天敌异色瓢虫Harmonia axyridis的影响, 并探讨其作用机理, 以便进行安全性评价并为科学使用提供理论依据。【方法】应用连叶浸渍法、浸渍法、点滴法和药膜法分别处理异色瓢虫卵、2龄幼虫、蛹和成虫, 观察苯氧威对4个虫态的影响。【结果】用浓度为0.0001 μg/mL的药液处理初产卵, 能抑制胚胎的发育; 但用高达20 000 μg/mL的药液处理发育2 d的卵, 幼虫仍可正常孵化; 用浓度高达4 000 μg/mL的药液浸渍2龄幼虫, 对幼虫的致死作用极小; 用浓度为0.0001 μg/头的药液处理当天蛹, 形成蛹 成虫中间体, 羽化的成虫畸形; 用浓度为0.0125 μg/mL的药液处理成虫, 24 h后成虫的生命力受到明显影响。【结论】苯氧威对异色瓢虫初产卵有明显的毒杀作用, 严重阻碍蛹到成虫的变态和影响成虫的存活。在田间使用该杀虫剂时, 要避开异色瓢虫的敏感期。     

多次交配对异色瓢虫雌虫寿命及适合度的影响

异色瓢虫Harmonia axyridis(Coleoptera:Coccinellidae)为多次交配型昆虫,通过设计不同的交配次数,观察并记录不同交配组的雌虫产卵量、卯孵化率及成虫寿命等参数,探究多次交配对异色瓢虫雌虫适合度的影响.结果 表明多次交配对雌性异色瓢虫成虫的寿命有显著影响(P<0.05),交配次数越多雌性瓢虫的寿命越短;单次交配组在交配后第一周的产卵量明显低于多次交配组,为55.00±17.90枚,而4次、7次、14次交配组产卵量分别为102.29±11.97枚、93.60±13.09枚和93.36±14.95枚;多次交配可以提高异色瓢虫卵的孵化率,多次交配组卵的孵化率明显高于单次交配组,其中7次交配组最高(88.71%±0.29%),多次交配对异色瓢虫雌虫有直接利益,多次交配可以提高雌性异色瓢虫的适合度.     

Assessment of patch quality by ladybirds: role of larval tracks

Gravid females of the two-spot ladybird, Adalia bipunctata (L.), were deterred from ovipositing when kept in petri dishes that had previously contained conspecific larvae but not conspecific adults, or the larvae of another two species of ladybird, Adalia decempunctata (L.) and Coccinella septempunctata L. The deterrent effect was density dependent and mediated via a chloroform-soluble contact pheromone present in the larval tracks. Similarly, gravid females of C. septempunctata were deterred from ovipositing by conspecific larval tracks and chloroform extracts of these tracks, but not by the tracks or extracts of tracks of A. bipunctata larvae. That is, in ladybirds the larvae produce a species-specific oviposition-deterring pheromone. In the field, the incidence of egg cannibalism in ladybirds increases very rapidly with the density of conspecific eggs or larvae per unit area. Thus, in responding to the species specific oviposition deterring pheromone female ladybirds reduce the risk of their eggs being eaten and spread their offspring more equally between patches. Received: 14 March 1997 / Accepted: 26 August 1997     

Response of coccinellid larvae to conspecific and heterospecific larval tracks: a mechanism that reduces cannibalism and intraguild predation

Cannibalism, where one species feeds on individuals of its own species, and intraguild predation (IGP), where a predator feeds on other predatory species, can both pose significant threats to natural enemies and interfere with their biological control of pests. Behavioral mechanisms to avoid these threats, however, could help maintain superior pest control. Here, we ask whether larvae of Coccinella septempunctata (Coleoptera: Coccinellidae) and Harmonia axyridis (Coleoptera: Coccinellidae) respond to larval tracks deposited by the other and whether this behavioral response reduces the threat of cannibalism and IGP. In petri dish experiments, we show that both H. axyridis and C. septempunctata avoid foraging in areas with conspecific larval tracks. Using a method of preventing larvae from depositing tracks, we then demonstrate that the frequency of cannibalism is greater for both species when larvae are prevented from depositing tracks compared with when the tracks are deposited. For multi-species interactions we show in petri dish experiments that C. septempunctata avoids H. axyridis larval tracks but H. axyridis does not avoid C. septempunctata larval tracks, demonstrating an asymmetry in response to larval tracks that parallels the asymmetry in aggressiveness between these species as intraguild predators. On single plants, we show that the presence of H. axyridis larval tracks reduces the risk of IGP by H. axyridis on C. septempunctata. Our study suggests that larval tracks can be used in more ways than previously described, in this case by changing coccinellid larval behavior in a way that reduces cannibalism and IGP.     

Foraging efficiency and the fitness consequences of spatial marking by ladybeetle larvae

Marking and avoiding poor‐quality resources can be an important mechanism by which animals lacking a spatial memory can maximize their foraging efficiency. Here, we investigate the behaviour of larval Harmonia axyridis ladybeetles that leave chemical tracks as they forage. We built a model of an individual larva foraging for aphids, parameterized it using experimental data, and used the model to predict the effect of larval track production and detection on foraging efficiency, an important component of fitness. The model predicted that there is an optimal sensitivity of larvae to tracks which maximizes foraging efficiency; if the larva is too sensitive to tracks, it will avoid areas that might still contain resources, whereas if it is too insensitive, it will forage in areas that have depleted resources. Furthermore, the increased efficiency conferred by detecting tracks depends on the spatial arrangement of resources, with more aggregated resource distributions allowing greater benefits of detecting tracks. We tested the predictions of the model experimentally by measuring predation on aggregated versus dispersed soybean aphids by H. axyridis larvae whose ability to produce tracks was experimentally manipulated. The experiments corroborated the results of the model: larvae that could produce tracks consumed more aphids than those that could not, and this difference was greatest when aphids were aggregated among plants. Our results suggest that larval tracks play an important role in foraging efficiency, and we discuss implications for the evolution of larval track production and detection in ladybeetles.     

Effect of cannibalism and predation on the larval performance of two ladybird beetles

The relative impact of cannibalism and predation on the development and survival of fourth instar larvae was assessed in two species of aphidophagous ladybird beetles, Coccinella septempunctata and Harmonia axyridis. The effect of eating aphids, conspecific larvae or heterospecific larvae on larval performance differed in the two species: aphids were the best food for C. septempunctata and survival of C. septempunctata larvae was significantly lower when offered heterospecific larvae rather than conspecific larvae or aphids as food, indicating that H. axyridis larvae were not suitable food for C. septempunctata. However, as the different foods did not affect the larval performance of H. axyridis, this species appears to be more polyphagous. Both intraguild predation by the aggressive larvae of H. axyridis and the polyphagous food habit of this species may account for its dominance in ladybird assemblages and its displacing other ladybird beetles in several places in the world.     

Asymmetry of larval diet breadth and oviposition preference in Leptinotarsa undecimlineata

The relationship between preference and performance was studied under laboratory conditions for larvae and adult females of Leptinotarsa undecimlineata (Stål) (Coleoptera: Chrysomelidae). Leptinotarsa undecimlineata feeds exclusively on Solanum lanceolatum L. (Solanaceae) in the centre of Veracruz, Mexico. A common sympatric species, Solanum myriacanthum Dunal, is not used as host. We conducted a series of laboratory experiments to detect reasons for the exclusive use of one host plant. Leptinotarsa undecimlineata larvae were reared under laboratory conditions on both plant species, Solanum lanceolatum and S. myriacanthum . Length of larval stages, pupal weight, and percent adult eclosion were compared, and larval preference for both Solanum species was tested. Upon eclosion, adult females were exposed to each of the plants, and the effect of larval diet on adult preference was determined. Oviposition on both Solanum species was observed in no-choice tests. Larvae showed no significant preferences for either plant species. Pupal weight, however, was significantly higher on S. lanceolatum . Female beetles significantly preferred S. lanceolatum leaves, and no effect of preimaginal conditioning was found. Females reproduced in lower numbers after feeding on S. myriacanthum , oviposition initiated later, and females laid fewer eggs than females fed with S. lanceolatum . No female accepted S. myriacanthum for oviposition. Results obtained suggest that the potential host breadth of L. undecimlineata is broader in larvae than in female beetles.     

Butterfly oviposition preference is not related to larval performance on a polyploid herb

The preference–performance hypothesis predicts that female insects maximize their fitness by utilizing host plants which are associated with high larval performance. Still, studies with several insect species have failed to find a positive correlation between oviposition preference and larval performance. In the present study, we experimentally investigated the relationship between oviposition preferences and larval performance in the butterfly Anthocharis cardamines. Preferences were assessed using both cage experiments and field data on the proportion of host plant individuals utilized in natural populations. Larval performance was experimentally investigated using larvae descending from 419 oviposition events by 21 females on plants from 51 populations of two ploidy types of the perennial herb Cardamine pratensis. Neither ploidy type nor population identity influenced egg survival or larval development, but increased plant inflorescence size resulted in a larger final larval size. There was no correlation between female oviposition preference and egg survival or larval development under controlled conditions. Moreover, variation in larval performance among populations under controlled conditions was not correlated with the proportion of host plants utilized in the field. Lastly, first instar larvae added to plants rejected for oviposition by butterfly females during the preference experiment performed equally well as larvae growing on plants chosen for oviposition. The lack of a correlation between larval performance and oviposition preference for A. cardamines under both experimental and natural settings suggests that female host choice does not maximize the fitness of the individual offspring.     

Larval Competition, Adult Fitness, and Reproductive Strategies in the Acoustically Orienting Ormiine Homotrixa alleni (Diptera: Tachinidae)

Homotrixa alleni is a gregarious endoparasitoid fly that attacks adult male Sciarasaga quadrata (Orthoptera: Tettigoniidae) in southwestern Western Australia. Gravid female flies acoustically orient to their host's call and deposit live first-instar larvae upon or near their calling host. Up to 16 larvae may be found developing in the one host, and since only calling adult male S. quadrata are parasitized, host size and hence larval resources are essentially fixed at parasitism. This study examines parasitism by H. alleni in relation to intraspecific larval competition and adult fitness. The mean number of larvae emerging per host failed to increase significantly beyond a clutch size of four. Mean pupal weight and survival to the adult stage decreased linearly with increasing clutch size across the entire range of clutch sizes examined. Within a clutch, heavier pupae successfully completed pupal development significantly more often than lighter pupae. Pupal weight was directly related to adult size, with adult males being significantly larger than adult females at any given pupal weight. Female body size was positively correlated with fecundity. The size distribution of emerging females was normally distributed, while the distribution of searching gravid females collected at acoustic traps in the field was significantly skewed toward larger flies, suggesting yet another fitness benefit associated with large size. Using fecundity and survival to adulthood as our measure of fitness we calculated the optimal clutch size maximizing fitness per host to be seven, which exceeds the majority of observed clutch sizes in the field. Uncertainties associated with larvae successfully entering the host following larviposition are likely to reduce clutch sizes of H. alleni below this optimum in the field.     

Selection of large host plants for oviposition by a monophagous leaf beetle: nutritional quality or enemy‐free space?

Abstract.  1. Oviposition site selection is crucial for the reproductive success of herbivorous insects. According to the preference–performance hypothesis, females should oviposit on host plants that enhance the performance of their offspring. More specifically, the plant vigour hypothesis predicts that females should prefer large and vigorously growing host plants for oviposition and that larvae should perform best on these plants.
2. The present study examined whether females of the monophagous leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae) prefer to oviposit on large host plant individuals of the meadow clary and whether large host plants are of higher nutritional quality than small host plants. Subsequently, it was tested whether the female preference correlates with offspring performance and survival.
3. In the field, females preferred large host plant individuals for oviposition and host plant quality, i.e. leaf nitrogen content, was significantly higher in leaves of large than of small host plants.
4. In the laboratory, larval development time was shorter on leaves of large host plant individuals than on small host plant individuals, but this could not be shown in the field.
5. However, a predator-exclusion experiment in the field resulted in a higher survival of larvae on large host plants than on small host plants when all predators had free access to the plants. On caged host plants there was no difference in survival of larvae between plant size categories.
6. It is concluded that females of C. canaliculata select oviposition sites that enhance both performance and survival of their offspring, which meets the predictions of the plant vigour hypothesis.     

The effect of parasitism by Aphelinus abdominalis and drought on the walking movement of aphids

The effect of simulated plant stress and parasitism by Aphelinus abdominalis (Dalman) on the mobility of four species of aphids was investigated. The aphids were placed on water stressed potted plants or on excised leaf segments on dry or moist filter-paper in Petri dishes. Winter wheat (Triticum aestivum) was infested with Metopolophium dirhodum (Walker), Sitobion avenae (F.) and Rhopalosiphum padi (L.) (segments only), aubergine (Solanum melongena) leaf segments with Macrosiphum euphorbiae (Thomas). The aphids that moved off the plants were removed and their development stage determined at 24-h (drought-stressed plants) or 3-h (leaf segments) intervals. On intact plants, aphid larvae were reluctant to move, and only moved after moulting into adults. On cut leaves, young 1st and 2nd instar larvae were more reluctant to move than 3rd and 4th instar larvae and adults. The numbers moving were initially positively correlated with aphid population density, and in M. euphorbiae occurred mainly during the night. Depending on aphid species and parasitoid age, parasitism by A. abdominalis retarded or accelerated movement, but the differences between young and old larvae and adults persisted after parasitism. A. abdominalis lays male eggs in small hosts and female eggs in large hosts. Consequently, its sex ratio was affected by differential movement of the host aphids of the male and female parasitoids. Old larvae and adult aphids readily moved and carried off female parasitoids, while the small aphids were more likely to remain and give rise to male-biased sex ratios.     

甜菜夜蛾对不同寄主植物的产卵和取食选择

为了探讨甜菜夜蛾Spodoptera exigua对不同寄主植物的产卵选择及成虫产卵选择与幼虫取食选择间的关联度, 本研究选取玉米、豇豆、甘蓝、黄瓜、棉花、辣椒和番茄7种植物进行了选择性和非选择性实验研究, 并采用Y型嗅觉仪测定了成虫对其中3种寄主植物及其挥发物抽提物的趋性。结果表明：在田间非选择性实验中, 甜菜夜蛾在不同寄主植物上的落卵量依次为：玉米>辣椒>棉花>黄瓜、豇豆、番茄>甘蓝。Y型嗅觉仪的行为测定表明, 雌成虫对玉米及其挥发物抽提物的趋性最强, 黄瓜次之, 对甘蓝的趋性最弱, 这与雌虫的产卵选择性一致。不同龄期甜菜夜蛾幼虫对寄主植物的取食选择性有所不同, 且随观测时间的延长有所改变;低龄幼虫对豇豆、玉米和黄瓜的选择性较强, 对甘蓝、番茄、辣椒和棉花的取食选择性则较弱, 高龄幼虫对辣椒也具有较强的选择性;5龄幼虫对寄主植物的选择性不如低龄幼虫明显。结果显示, 甜菜夜蛾对不同寄主植物的产卵选择性显著不同, 植物抽提物在雌成虫的产卵选择中具有重要作用, 甜菜夜蛾对寄主植物的产卵选择性和幼虫取食选择性并不一致。