不同猎物及密度对巴氏新小绥螨和拉戈钝绥螨同类相残和集团内捕食作用的影响

明确不同猎物及密度下巴氏新小绥螨Neoseiulus barkeri与拉戈钝绥螨Amblyseius largoensis(Muma)的同类相残和集团内捕食作用,为其协同应用控制橡胶树害螨提供依据。在室温27±1℃、湿度75%±5%、光周期12 L:12 D条件下,以六点始叶螨Eotetranvchus sexmaculatus(Riley)、比哈小爪螨Oligonychus biharen(Hirst)和东方真叶螨Eutetranychus orientalis(klein)为集团外猎物,观察巴氏新小绥螨和拉戈钝绥螨对集团内和集团外猎物的捕食选择行为,以及不同集团外猎物密度下两种捕食螨对同种和异种捕食螨的捕食作用。巴氏新小绥螨和拉戈钝绥螨对异种个体及集团外不同猎物的捕食偏好性及捕食时间存在明显差异。巴氏新小绥螨偏好取食集团外猎物,异种捕食螨拉戈钝绥螨残存率达到80.00%以上;拉戈钝绥螨偏好取食集团外猎物六点始叶螨和比哈小爪螨,而当东方真叶螨存在时,其更偏好取食异种捕食螨巴氏新小绥螨(残存率为26.67%);发生集团内捕食时,拉戈钝绥螨为集团内捕食者,而巴氏新小绥螨为集团内猎物。集团外猎物密度可显著影响巴氏新小绥螨和拉戈钝绥螨相残作用,尤以猎物六点始叶螨对巴氏新小绥螨和东方真叶螨对拉戈钝绥螨影响最为明显,其充足时比无猎物时捕食量分别下降了68.85%和62.90%。巴氏新小绥螨和拉戈钝绥螨的集团内捕食分别以比哈小爪螨和六点始叶螨的影响最大,猎物充足时比无猎物时捕食量下降了80.00%和69.44%,但拉戈钝绥螨在以东方真叶螨为猎物时集团内捕食受猎物密度影响较小,猎物充足时取食量与猎物不足时接近,比无猎物时捕食量只下降20.83%。集团外猎物六点始叶螨、比哈小爪螨存在时,巴氏新小绥螨和拉戈钝绥螨表现为偏好选择集团外猎物,密度增加对两种植绥螨的同类相残和集团内捕食作用有明显抑制作用,但东方真叶螨充足与否,拉戈钝绥螨对巴氏新小绥螨的集团内捕食作用影响差异不显著。     

两种植绥螨的同类相残和集团内捕食作用

巴氏新小绥螨(Neoseiulus barkeri)和黄瓜新小绥螨(N.cucumeris)是两种多食性植绥螨,主要捕食叶螨和蓟马等,目前在我国广泛应用于农业生物防治中.本文研究了这两种植绥螨种内的同类相残(cannibalism)和种间的集团内捕食作用(intraguild predation)以及相互之间的攻击强度,以明确两者之间的相互关系,为合理构建天敌组合及评估生物防治的作用提供依据.结果显示:两种植绥螨对同种或异种幼螨的捕食量最大,其次是若螨,而对卵的捕食量极低.两种植绥螨对异种幼螨或若螨的捕食量均极显著高于对同种幼螨或若螨的捕食量.可见,无其他猎物存在情况下,两种植绥螨同时发生时更倾向于发生种间的集团内捕食.而巴氏新小绥螨对异种幼螨或若螨的捕食量均高于黄瓜新小绥螨对异种幼螨或若螨的捕食量,并且巴氏新小绥螨和黄瓜新小绥螨相比,巴氏新小绥螨对异种幼螨的攻击性更强,因此当这两种植绥螨发生集团内捕食时,巴氏新小绥螨是潜在的集团内捕食者,而黄瓜新小绥螨是潜在的集团内猎物.     

两种捕食螨对苹果园叶螨的控制效果

【目的】以螨治螨是害虫生物防治的一个重要部分,也是果园害虫生态控制的重要措施。通过在苹果园人为释放捕食螨的方法,定量分析加州新小绥螨Neoseiulus californicus(McGregor)和东方钝绥螨Amblyseiusorientalis(Ehara)对苹果园2种害螨(苹果全爪螨Panonychusulmi(Koch)和山楂叶螨TetranychusviennensisZacher)捕食效果,为开展果园害虫生态调控提供科学依据。【方法】于2019年5-10月份在胶东半岛烟台市牟平区果园中释放加州新小绥螨和东方钝绥螨,比较分析释放捕食螨区域与对照苹果树上苹果全爪螨和山楂叶螨种群数量的变化。【结果】2种捕食螨均能适应当地果园生态环境,释放后能够迅速发挥控害作用。其中,加州新小绥螨对叶螨的控制作用达到84.8%-100%,东方钝绥螨对叶螨的控制作用达到90%-100%,且东方钝绥螨的防治效果略优于加州新小绥螨。【结论】加州新小绥螨和东方钝绥螨2种捕食螨在胶东半岛对苹果叶螨防控效果比较理想,均可作为苹果园叶螨生物防治的天敌。     

纽氏钝绥螨、尼氏钝绥螨及其猎物—桔全爪螨生态学特性的比较研究

本文从天敌与猎物的种群内禀增长力,天敌对猎物不同密度的功能反应及数值反应三个方面来评价和比较纽氏钝绥螨、尼氏钝绥螨时其猎物——枯全爪螨的控制作用。在五种温度下,两种捕食螨的种群内禀增长力都大于桔全爪螨。它们对猎物的功能反应属HollingⅡ型。尼氏钝绥螨的捕食量大于纽氏钝绥螨,在25℃时两种捕食螨捕食量最大,应用Rogers的模型能较好地对试验结果进行模拟。尼氏钝绥螨对桔全爪不同虫态的取食不存在选择效应,纽氏钝绥螨则嗜食若螨和幼螨。两种捕食螨对桔全爪螨的数值反应表明,仅供给桔全爪螨雌成螨作为食物,对两种捕食螨都不利,尤其对尼氏钝绥螨更为明显。综上所述,两种捕食螨能比较有效地控制桔全爪螨种群,当猎物密度较高时,尼氏钝绥螨控制效果优于纽氏钝绥螨,但纽氏钝绥螨控制效果优于纽氏钝绥螨,但纽氏钝绥螨田间种群数量比尼氏钝绥螨稳定。柑桔园中存在其它补充食物时对这两种捕食敌有利。     

加州新小绥螨和巴氏新小绥螨对二斑叶螨的捕食能力比较

【目的】比较加州新小绥螨Neoseiulus californicus和巴氏新小绥螨Neoseiulus barkeri对二斑叶螨Tetranychus urticae的捕食能力,为果园二斑叶螨生物防治剂的选择提供依据。【方法】采用捕食功能反应的方法研究加州新小绥螨和巴氏新小绥螨雌成螨对二斑叶螨各螨态的捕食作用。【结果】加州新小绥螨和巴氏新小绥螨雌成螨对二斑叶螨各螨态的捕食功能反应均属于HollingⅡ型,对二斑叶螨各螨态的捕食能力均随着螨态的增大而降低,对卵的捕食能力最强,其次是幼螨、第一若螨、第二若螨、成螨。巴氏新小绥螨对二斑叶螨卵、幼螨的捕食能力强于加州新小绥螨,功能反应参数a/Th值分别高出55.2%和30.1%,而加州新小绥螨对二斑叶螨第一若螨、第二若螨的捕食能力强于巴氏新小绥螨,a/Th值分别高出67.5%和114.5%,两种捕食螨对二斑叶螨雌成螨的捕食能力相当,a/Th值均为4.5。加州新小绥螨和巴氏新小绥螨均对二斑叶螨的卵和幼螨表现出嗜食性,而对若螨和成螨没有嗜食性。两种捕食螨对二斑叶螨的捕食存在种内干扰,加州新小绥螨的干扰系数(0.328)大于巴氏新小绥螨(0.324)。【结论】在室内环境稳定的条件下,加州新小绥螨对二斑叶螨的捕食能力强于巴氏新小绥螨。     

巴氏新小绥螨对猎物搜寻能力的研究

巴氏新小绥螨Neoseiulus barkeri(Hughes)是一种多食性捕食螨,主要捕食叶螨和蓟马等。因其捕食范围广,捕食量相对较大,且易人工繁殖,因此,被广泛应用于农业生物防治中。本文利用温室的释放-回收实验研究了巴氏新小绥螨对截形叶螨Tetranychus truncatus和西花蓟马Frankliniella occidentalis(Pergande)的搜寻能力。实验共设3个处理:(1)叶螨为害植株与清洁植株;(2)蓟马虫害植株与清洁植株;(3)蓟马、叶螨混合为害植株与清洁植株。当捕食螨释放于清洁黄瓜植株和虫(螨)害黄瓜植株交替排列的六角结构的中心时,2种害虫(螨)不论是单独危害还是混合危害,巴氏新小绥螨回收比例随着时间的延长逐渐趋于平缓。释放后1 d之内,叶螨、蓟马及混合猎物处理中回收到的捕食螨分别占释放总量的65.25%±1.61%、62.75%±1.31%和81.75%±2.14%,并且虫(螨)害植株上回收到的捕食螨数量明显比清洁植株多,叶螨、蓟马及混合猎物危害植株回收的捕食螨量分别占释放总量的53.5%±5.6%、49.5%±3.6%和74.0%±2.7%。因此,巴氏新小绥螨对这2种猎物及其混合物均有较强的搜寻能力,能够有效定位作物中有猎物的植株。同时对利用一种捕食螨生物防治温室中同时发生的2种害虫(螨)的可能性进行了讨论。     

巴氏钝绥螨对柑桔全爪螨的捕食效能

本文研究了巴氏钝绥螨Amblyseius barkeri的雌成螨、雄成螨、若螨在实验条件下对柑桔全爪螨的捕食效能。结果表明：5个实验温度条件下（16、20、24、28和32℃，RH85％），利用椭圆食粉螨饲养的巴氏钝绥螨Panonychus citri对柑桔全爪螨均有较强的捕食能力；巴氏钝绥螨对柑桔全爪螨的功能反应均属于Holling Ⅱ型。在实验温度范围内，各螨态对柑桔全爪螨的控制能力（α／Th值）随温度升高而增大，在28℃时达到峰值；同一温度条件下，雌成螨的捕食能力最大，若螨其次，雄成螨的捕食能力最弱；在猎物密度固定时，由于巴氏钝绥螨个体之间存在相互竞争和相互干扰作用，随着捕食者密度的提高，捕食者平均捕食量逐渐减少。巴氏钝绥螨对各螨态柑桔全爪螨的取食有选择性，柑桔全爪螨的幼若螨是巴氏钝绥螨的嗜好虫态。     

巴氏新小绥螨对同一栖息地枸杞瘿螨的捕食功能反应

枸杞瘿螨Aceria pallida Keifer（Acari: Eriophyoidae）是枸杞上为害最严重的有害生物之一。近期在内蒙古地区发现植绥螨巴氏新小绥螨Neoseiulus barkeri Hughes（Acari: Phytoseiidae）与枸杞瘿螨可同时发生在野生枸杞上。为评价巴氏新小绥螨对枸杞瘿螨的捕食潜力,本研究在室内25±1℃、RH 65%±10%、16 L∶8 D的条件下,研究了巴氏新小绥螨对不同密度枸杞瘿螨成螨（30、50、70、90、110、130、150、170头）的捕食功能反应及搜寻效应。结果表明,巴氏新小绥螨的雌、雄成螨对枸杞瘿螨成螨的捕食功能反应均为Holling-II型,即巴氏新小绥螨雌、雄成螨的捕食量随着猎物密度的增加而增加,一直到猎物密度较高时趋于稳定;而巴氏新小绥螨雌、雄成螨的搜寻效应随着猎物密度的增加而降低。巴氏新小绥螨雌成螨对相同密度下的枸杞瘿螨成螨的捕食量均高于雄成螨,而且雌成螨的搜寻效应也强于雄成螨。巴氏新小绥螨雌成螨的攻击率（α=4.4121）高于雄成螨（α=2.4403）,而雌成螨的处理时间（Th =0.0094 d）短于雄成螨（Th=0.0196 d）;雌、雄成螨的理论最大日捕食量（T/Th）分别为106.61头和51.02头。研究结果显示巴氏新小绥螨对枸杞瘿螨有较好的捕食潜力,性别对巴氏新小绥螨捕食枸杞瘿螨的功能反应有显著影响。     

加州新小绥螨在不同温度下对 六点始叶螨的捕食效能

为明确加州新小绥螨对橡胶六点始叶螨的控害潜能,系统研究了21℃、24℃、27℃、30℃、33℃5个不同温度条件下加州新小绥螨对六点始叶螨各螨态的捕食效能和自身密度干扰效应。结果表明:加州新小绥螨对六点始叶螨若螨、幼螨和卵的选择系数分别为0.71、1.75和0.54。在21℃～33℃条件下,加州新小绥螨对不同螨态六点始叶螨的功能反应均能很好地拟合Holling-II型圆盘方程,其对六点始叶螨雌成螨、若螨、幼螨的捕食效能(a/Th)在30℃时最强,分别达19.91、44.90、189.45头/d,对叶螨卵的捕食能力在不同温度间差异不显著。在同一温度条件下,加州新小绥螨对不同螨态六点始叶螨的捕食量大小依次为:幼螨若螨成螨卵。在相同的猎物密度条件下,加州新小绥螨的捕食作用率随其自身密度的增加而逐渐降低,说明加州新小绥螨存在种内竞争和自我干扰作用,自身干扰系数为0.349。     

两种植绥螨种内和种间捕食及适合度

【目的】通过研究斯氏钝绥螨Amblyseius(Typhlodromips)swirskii和胡瓜新小绥螨Neoseiulus cucumeris这两种外来植绥螨种内和种间的捕食关系及适合度,为斯氏钝绥螨的释放应用前的风险评估及与胡瓜新小绥螨的联合释放技术提供理论依据。【方法】在无共享猎物的条件下,分别为两种雌成螨提供同种和异种的卵、同种和异种的幼螨、同种和异种的若螨,测定其对同种和异种不同个体的捕食选择性及捕食量,并比较两种植绥螨捕食后的适合度（产卵率和存活率）的差异。【结果】两种植绥螨互为捕食者,斯氏钝绥螨为集团内捕食者的几率高于胡瓜新小绥螨;两种植绥螨发生同类相残的几率无显著差异（χ²=0.118,df=1,P=0.732）。两种植绥螨对幼螨的捕食量显著高于对若螨、卵的捕食量（斯氏钝绥螨：F_(2,114)=66.27,P<0.0001;胡瓜新小绥螨：F_(2,114)=50.39,P<0.0001）,而且两种植绥螨对异种幼螨和若螨的捕食量均显著高于对同种个体的捕食量。两种植绥螨捕食幼螨后的产卵率均显著高于捕食若螨后的产卵率（斯氏钝绥螨：t=5.774,df=26,P<0.0001;胡瓜新小绥螨：t=3.334,df=26,P=0.0026）,斯氏钝绥螨捕食异种个体后的产卵率显著高于捕食同种个体后的产卵率（t=2.854,df=26,P=0.008 4）。两种植绥螨捕食不同发育阶段（幼螨和若螨）的存活率无显著差异;但斯氏钝绥螨捕食异种个体后的存活率显著高于捕食同种个体后的存活率（t=2.196,df=26,P=0.0372）。【结论】两种植绥螨更倾向于发生交互集团内捕食作用而非同类相残;两种植绥螨捕食幼螨比捕食若螨更利于产卵;对于斯氏钝绥螨,异种个体是比同种个体更适合的食物来源。     

有益真绥螨与巴氏新小绥螨的集团内捕食和同类相残作用

【目的】有益真绥螨Euseius utilis是北方地区广泛分布的一种多食性植绥螨,而巴氏新小绥螨Neoseiulus barkeri目前在我国广泛应用于农业害虫的生物防治中。本研究旨在对巴氏新小绥螨在本地的应用进行风险评估及为与有益真绥螨的联合释放提供依据。【方法】本研究在室内通过一系列实验,比较了实验室饲养的巴氏新小绥螨和采自内蒙古农业大学校园的有益真绥螨的雌成螨对同种或异种未成熟螨的捕食量、存活时间及产卵量的差异,检测了有益真绥螨与巴氏新小绥螨两种植绥螨相互之间的攻击强度以及种内和种间的相互作用。【结果】两种植绥螨都难以刺吸同种或异种植绥螨的卵,而对同种或异种植绥螨幼螨的捕食量最大,其次是对若螨。在无共同食物的情况下,有益真绥螨雌成螨对同种植绥螨幼螨的攻击性比对异种植绥螨幼螨的攻击性强(BreslowDay检验:χ~2=13.84,df=1,P0.001),且有益真绥螨对同种植绥螨幼螨的捕食量(9.10±1.65头)高于对异种植绥螨幼螨的捕食量(5.31±1.43头)(T检验:t=5.487,P0.001),巴氏新小绥螨对异种植绥螨幼螨的捕食量(7.48±0.75头)高于对同种植绥螨幼螨的捕食量(4.75±0.58头)(T检验:t=9.110,P0.05)。【结论】有益真绥螨更倾向于捕食同种幼螨而发生同类相残;巴氏新小绥螨更倾向于捕食异种幼螨而发生集团内捕食。     

Prey preference,intraguild predation and population dynamics of an arthropod food web on plants

The theory of intraguild predation (IGP) largely studies effects on equilibrium densities of predators and prey, while experiments mostly concern transient dynamics. We studied the effects of an intraguild (IG) predator, the bug Orius laevigatus, on the population dynamics of IG-prey, the predatory mite Phytoseiulus persimilis, and a shared prey, the phytophagous two-spotted spider mite Tetranychus urticae, as well as on the performance of cucumber plants in a greenhouse. The interaction of the predatory mite and the spider mite is highly unstable, and ends either by herbivores overexploiting the plant or predators exterminating the herbivores. We studied the effect of IGP on the transient dynamics of this system, and compared the dynamics with that predicted by a simple population-dynamical model with IGP added. Behavioural studies showed that the predatory bug and the predatory mite were both attracted to plants infested by spider mites and that the two predators did not avoid plants occupied by the other predator. Observations on foraging behaviour of the predatory bug showed that it attacks and kills large numbers of predatory mites and spider mites. The model predicts strong effects of predation and prey preference by the predatory bugs on the dynamics of predatory mites and spider mites. However, experiments in which the predatory bug was added to populations of predatory mites and spider mites had little or no effect on numbers of both mite species, and cucumber plant and fruit weight.     

Intraguild Interactions Between the Predatory Mites Neoseiulus californicus and Phytoseiulus persimilis

Species at the same trophic level may interact through competition for food, but can also interact through intraguild predation. Intraguild predation is widespread at the second and third trophic level and the effects may cascade down to the plant level. The effects of intraguild predation can be modified by antipredator behaviour in the intraguild prey. We studied intraguild predation and antipredator behaviour in two species of predatory mite, Neoseiulus californicus and Phytoseiulus persimilis, which are both used for control of the two-spotted spider mite in greenhouse and outdoor crops. Using a Y-tube olfactometer, we assessed in particular whether each of the two predators avoids odours emanating from prey patches occupied by the heterospecific predator. Furthermore, we measured the occurrence and rate of intraguild predation of different developmental stages of P. persimilis and N. californicus on bean leaves in absence or in presence of the shared prey. Neither of the two predator species avoided prey patches with the heterospecific competitor, both when inexperienced with the other predator and when experienced with prey patches occupied by the heterospecific predator. Intraguild experiments showed that N. californicus is a potential intraguild predator of P. persimilis. However, P. persimilis did not suffer much from intraguild predation as long as the shared prey was present. This is probably because N. californicus prefers to feed on two-spotted spider mites rather than on its intraguild prey.     

Diet‐dependent intraguild predation between the predatory mites Neoseiulus californicus and Neoseiulus cucumeris

Based on the hypothesis that matching diets of intraguild (IG) predator and prey indicate strong food competition and thus intensify intraguild predation (IGP) as compared to non‐matching diets, we scrutinized diet‐dependent mutual IGP between the predatory mites Neoseiulus cucumeris and N. californicus. Both are natural enemies of herbivorous mites and insects and used in biological control of spider mites and thrips in various agricultural crops. Both are generalist predators that may also feed on plant‐derived substances such as pollen. Irrespective of diet (pollen or spider mites), N. cucumeris females had higher predation and oviposition rates and shorter attack latencies on IG prey than N. californicus. Predation rates on larvae were unaffected by diet but larvae from pollen‐fed mothers were a more profitable prey than those from spider‐mite fed mothers resulting in higher oviposition rates of IG predator females. Pollen‐fed protonymphs were earlier attacked by IG predator females than spider‐mite fed protonymphs. Spider mite‐fed N. californicus females attacked protonymphs earlier than did pollen‐fed N. californicus females. Overall, our study suggests that predator and prey diet may exert subtle influences on mutual IGP between bio‐control agents. Matching diets did not intensify IGP between N. californicus and N. cucumeris but predator and prey diets proximately influenced IGP through changes in behaviour and/or stoichiometry.     

Intraguild predation of Orius tristicolor by Geocoris spp. and the paradox of irruptive spider mite dynamics in California cotton

It is paradoxical when a community of several natural enemies fails to control a pest population when it can be shown experimentally that single members of the natural enemy community are effective control agents when tested individually. This is the case for spider mites, Tetranychus spp., in California cotton. Spider mites exhibit irruptive population dynamics despite that fact that experiments have shown that there are at least four predators (Galendromus occidentalis, Frankliniella occidentalis, Orius tristicolor, and Geocoris spp.) that, when tested singly, can suppress mite populations. One possible explanation for the paradox is intraguild predation, wherein one predator consumes another. Here, I evaluate the hypothesis that intraguild predation is a strong interaction among spider mite predators. I report manipulative field experiments, focal observations of freely foraging predators in the field, and population survey data that suggest that the minute pirate bug O. tristicolor, is subject to strong predation by other members of the predator community, and in particular by Geocoris spp. These results, combined with the results of prior work, suggest that pervasive intraguild predation among spider mite predators may explain the pest status of Tetranychus spp. in cotton.     

Oviposition Behavior of Interacting Predatory Mites: Response to the Presence of Con- and Heterospecific Eggs

Oviposition behavior may be affected by the presence of potential future competitors, mates, or predators of offspring. We examined patch choice, oviposition site preference and egg production in the predaceous mites Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae) when given a choice between paired spider mite patches with and without conspecific eggs, with and without heterospecific eggs, and with conspecific or heterospecific eggs. Neoseiulus californicus females had no patch preference and distributed their eggs randomly in all choice situations. This was also the case with P. persimilis females given a choice between patches with and without conspecific eggs and between patches with either con- or heterospecific eggs. Phytoseiulus persimilis females confronted with patches with and without heterospecific eggs preferentially stayed and oviposited in the predator free patches. We discuss the oviposition strategies of P. persimilis and N. californicus with respect to food competition, cannibalism and intraguild predation.     

东亚小花蝽对西方花蓟马和二斑叶螨的捕食选择性

多食性天敌对猎物的捕食选择性及猎物密度对天敌捕食的干扰作用直接影响到天敌对不同猎物的控制作用.在实验室条件下研究了东亚小花蝽对西方花蓟马和/或二斑叶螨不同虫态的捕食选择性,以及两猎物中一种猎物的密度变化对小花蝽取食另一种猎物的影响.结果如下:东亚小花蝽5龄若虫和成虫对西方花蓟马2龄若虫的捕食选择性均强于对其成虫,对二斑叶螨的选择性为雌成螨>若螨>幼螨.实验中西方花蓟马2龄若虫是东亚小花蝽最喜好的虫态.二斑叶螨雌成螨密度固定为60头/19.63cm2,西方花蓟马若虫密度从10增加到60时显著地减少了东亚小花蝽对二斑叶螨的取食.反之,固定西方花蓟马同样密度,增加二斑叶螨密度却没有显著改变小花蝽对西方花蓟马的取食.此结果进一步表明,西方花蓟马是东亚小花蝽更喜好的猎物.     

拟小食螨瓢虫捕食六点始叶螨的初步观察

在室内以六点始叶螨Eotetranychus sexmaculatus(Riley)为猎物观察了拟小食螨瓢虫Stethorusparapauperculus Pang的发育历期、捕食量、捕食作用及干扰效应。研究结果表明:拟小食螨瓢虫取食六点始叶螨时完成一个世代需23.2 d,幼虫1～4龄的捕食量分别为9.5、14.5、19.5、64.2头六点始叶螨成螨;成虫期对六点始叶螨成螨的捕食量高达880.4头,拟小食螨瓢虫对六点始叶螨的捕食作用符合HollingⅡ方程,拟合的模型方程为Na=1.3843 N/(1+0.0231N),日均最大捕食量为43.29头;拟小食螨瓢虫的捕食率与个体间的干扰效应用Hassell-Varley(1959)模型拟合为E=0.4690P-0.5470。     

Intra- and interspecific predation by adult female Metaseiulus occidentalis and Typhlodromus pyri (Acari: Phytoseiidae) when provisioned with varying densities and ratios of Tetranychus urticae (Acari: Tetranychidae) and phytoseiid larvae

The phytoseiid mites Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Schueten are used together and alone as biological control agents against tetranychid pest mites of apple. Their effectiveness as control agents may be impacted by intraguild predation. The effects of prey species and prey density on the rates of inter- and intraspecific predation and oviposition by these two predators were investigated through a series of experiments. Adult female predators were given prey as mixed populations of phytoseiid larvae and larvae of a more preferred species, the spider mite, Tetranychus urticae Koch, at different densities and ratios. Typhlodromus pyri, more of a generalist predator, showed higher rates of predation and cannibalism on phytoseiid immatures at most prey densities and ratios. Manly preference indices indicated that T. pyri switched to feed on phytoseiid larvae at higher prey levels and ratios of T. urticae than M. occidentalis. This greater ability to use phytoseiid larvae as prey may help stabilize T. pyri populations when more preferred prey is unavailable. This may, in part, explain the observed persistence of T. pyri populations when M. occidentalis populations were decreasing in orchard test plots.     

Influence of extraguild prey density on intraguild predation by heteropteran predators: A review of the evidence and a case study

Heteropteran predators constitute an important component of predatory guilds in terrestrial and aquatic ecosystems. Most heteropteran species have generalist diets, and intraguild predation has been documented in most heteropteran families. Zoophytophagous species also frequently engage in intraguild interactions. An increase in extraguild prey density is often predicted to reduce intraguild predation between guild members by providing abundant alternate prey. However, an increase of extraguild prey density may also be associated with an increase in the density of intraguild predators, which could instead strengthen intraguild predation. Evaluating the combined effect of these potentially opposing influences on intraguild predation is difficult. Most studies have been carried out in the laboratory, using artificially simplified communities of predators and prey and employing spatial and temporal scales that may not reflect field conditions. We review experimental studies examining how extraguild prey density influences the intensity of intraguild predation and then report an observational case study examining the influence of extraguild prey density on the intensity of intraguild predation at larger spatial and temporal scales in unmanipulated cotton fields. Fields with more abundant extraguild prey (aphids, mites) were not associated with elevated densities of intraguild predators, and were strongly associated with increased survival of intraguild prey (lacewing larvae). In this system, the ability of extraguild prey to relax the intensity of intraguild predation, as previously documented in small-scale field experiments, also extends to the larger spatial and temporal scales of commercial agriculture.