Host plants affect predator fitness via the nutritional value of herbivore prey: Investigation of a plant-aphid-ladybeetle system

The interactions among host plants(Medicago sativa L., cv. `OKO8' and Vicia faba L., cv. `Windsor'), aphid prey(Acyrthosiphon pisum Harris, Homoptera:Aphididae), and Coccinella septempunctata L. (Coleoptera: Coccinellidae) preimaginal biology were evaluated. Interactions were measured over a range of limiting daily prey levels (1.2 mg–16.4 mg)from each host plant colony. Compared withA. pisum reared on V. faba, A. pisum reared on M. sativa storedsignificantly more fatty acids which resultedin a 1.17-fold increase in available caloriesfor developing C. septempunctata. Theincreased survival, decreased developmentaltimes, and larger size of C.septempunctata supplied with A. pisumreared on M. sativa clearly demonstratehost plant effects at the third trophic level. At low very limiting daily prey levels, A. pisum reared on M. sativa were moresuitable prey for C. septempunctatasurvival, development, and adult size thanA. pisum reared on V. faba. Coccinella septempunctata survival ratios(larval), developmental times, and adult sizeconverged (were not statistically different)between host plants at higher daily A.pisum levels. These convergence's supportthe hypothesis that there were quantitativedifferences in the nutritional value ofaphids, as influenced by differences in fattyacids and subsequent nutritional levels(calories), between aphids reared on separateplant hosts. The observed tritrophicinteractions appear to be modulated by thebiochemical response of A. pisum to hostplants.     

STUDIES ON SELECTIVE TOXICITY OF SIX INSECTICIDES BETWEEN GREEN PEACH APHID AND LADYBIRDS

Abstract  The selective toxicity of six kinds of insecticides, including imidacloprid, imidacloprid + synergist (SV1), fenvalerate, endosulfan, methomyl and dimethoate, between the green peach aphid ( Myzus persicae Sulzer) and two species of ladybirds ( Coccinella septempunctata Linnaeus and Propylaea japonica Thunbery), was investigated in the laboratory. The reults showed that both imidacloprid WP and imidacloprid + synergist (SVl) EC possessed the highest toxicity to the aphids. Between C. septempunctata and M. persicae and between P. japonica and M. persicae , the selective toxicity ratios (STRs) of imidacloprid WP, imidacloprid+ synergist (SV1) EC and endosulfan EC were 37.6 and 13.0, 9.84 and 7.75, 54.0 and 7.28 respectively. All of them showed rather high selective toxicity. The STRs of fenvalerate EC, dimethoate EC and methomyl EC were all very low, ranging from 0.02 to 0.21, indicating their low degree of safety to the two species of ladybids. The results demomarated that imidacloprid WP and imidacloprid + SVl EC not only had rather high toxicity to the aphids, but also reduced strikingly the reproduction rate and fecundity of the survival aphids. Insecticides can induce the relative fitness of insects decrease. Among the six insecticides tested with M. persicae , the following were insecticides and the order of induction was: imidacloprid + SV1 imidacloprid endosulfan methomyl fenvalerate > dimethoate.     

麦田天敌消长演替规律及超长期预测的研究

通过聚类分析,在明确麦田天敌消长演变规律的基础上,采用时间序列分析法,建立麦田总体天敌和优势天敌七星瓢虫的超长期预测模型,经过2001年和2002年实际应用,季节水平模型、ARIMA模型的预测效果较好,并用这两种模型对未来三年麦田天敌的消长进行了超长期预测。     

十一星瓢虫在不同温度下的实验种群生命表

组建了十一星瓢虫在16℃、20℃、24℃、28℃和32℃下的实验种群生命表。结果表明：各 虫态的发育速率随温度的升高而加快,在16℃下世代的发育历期最长(64.2天),而32℃时仅为16.4天,24℃和28℃时分别为27.1天和21.5天。卵、幼虫、蛹和世代的发育起点温度分别为10.9℃,11.1℃,12.5℃和10.6℃,有效积温分别为40.9,110.3,39.7,359.4日·度。成虫寿命随温度升高而逐渐缩短,16℃时最长,为34.7天,在32℃下最短,为14.1天; 单雌产卵量在24℃时最高,平均为463.8粒,32℃时最低,为96.4粒。在恒温24℃～28℃内, 十一星瓢虫的种群趋势指数和内禀增长力较高, 种群加倍时间较短。16℃时种群增长受到较大制约,种群趋势指数仅为24℃时的10.7%,种群加倍时间约22.3天,为24℃时的4.1倍。32℃时十一星瓢虫的发育历期缩短,存活率、繁殖力降低。     

瓢虫和草蛉对小麦挥发物组分的行为及电生理反应

利用触角电位（electroantennogram, EAG）和嗅觉测定技术,比较分析了4种捕食性天敌昆虫七星瓢虫Coccinella septempunctata、龟纹瓢虫Propylaea japonica、中华通草蛉Chrysoperla sinica和大草蛉Chrysopa septempunctata对麦蚜取食诱导小麦挥发物的行为和电生理反应,揭示了瓢虫及草蛉类天敌昆虫的嗅觉反应特点。4种捕食性天敌昆虫对麦蚜取食诱导挥发物都有较高的EAG反应值,七星瓢虫和龟纹瓢虫对6-甲基-5_庚烯-2-酮、6-甲基-5-庚烯-2-醇的反应值较大;中华通草蛉和大草蛉对6-甲基-5-庚烯-2-醇和水杨酸甲酯的反应值较大,七星瓢虫对6-甲基-5-庚烯-2-醇的反应值最大,为0.96±0.18 mV;4种天敌昆虫对苯甲醛的EAG反应值较低,对反-2-己烯醛无反应。“Y”型管嗅觉测定结果表明,4种天敌昆虫对2-莰烯、6-甲基-5-庚烯-2-酮、6-甲基-5-庚烯-2-醇和水杨酸甲酯具有正趋性。说明4种多食性的捕食性天敌昆虫对麦蚜取食诱导挥发物各组分的嗅觉与行为反应各具特点;寄主麦蚜生境中的嗅觉线索在这4种捕食性天敌昆虫的寄主定位和生境选择中起重要作用。     

Resistance of F1, F2 and BC1 generations to maize dwarf mosaic virus in maize

Computer simulations with GTLAUS 3.7 were performed to investigate the influence of different cases of increasing temperatures on the tritrophic wheat ‐ cereal aphid ‐ predator interaction. Two cases of a temperature increase were defined: (1) homogenous increase by adding 3°C, and (2) comparable increase with relatively wanner nights. Both cases of increasing temperatures with similar daily average values resulted in a significant reduction of aphid infestation, but this reduction was smaller in scenarios with relatively higher night temperatures. But the results indicate only relatively small differences deriving from this particularly high night temperatures.     

Geographic variation in the habitat preference of a scarce predatory insect: evolutionary and conservation perspectives

1. While there has been considerable focus on prey occurrence as a factor determining the habitat preference of predators, the roles of other factors related to the habitat are less well characterised. 2. In aphidophagous ladybird beetles (Coleoptera: Coccinellidae), a number of species are more restricted in the habitats in which they live than are their prey. A number of such ladybirds appear to show geographic variation in habitat preference. 3. To better understand these phenomena, this study considered geographic variation in habitat preference in one such species, the 5-spot ladybird Coccinella quinquepunctata. Because of this ladybird's scarcity, a combination of over 20 years' observations, habitat surveys and online data was used to reach the study's conclusions. 4. The data collected indicate that the ladybird is specialised in pioneer habitats close to water, but broadens its range to non-riverine pioneer habitats in north-west continental Europe, where it is likely that a damper (micro)climate allows it to do so. Thus, microclimatic factors appear to be important in determining the habitat of this and probably other predators that are not constrained by prey occurrence. 5. Although threatened by river management elsewhere, in north-western Europe, this species clearly benefits from human activity, which creates many of the disturbed habitats it colonises there. This finding provides further support for the contention that many ladybirds are net beneficiaries of human influence, although they are often characterised as threatened.     

Stage and age-specific predation in four aphidophagous ladybird beetles

In the present study, stage- and age-specific predatory patterns and nutritional ecology attributes of four co-occurring aphidophagous ladybirds, namely, Coccinella septempunctata (L.), Coccinella transversalis F., Cheilomenes sexmaculata (F.) and Propylea dissecta (Mulsant) on pea aphid, Acyrthosiphon pisum (Harris) were investigated. Despite their lower consumption rates, smaller ladybirds (C. sexmaculata and P. dissecta) and earlier instars were efficient converters of aphid prey with higher relative growth rates, over the respective larger ladybirds (C. septempunctata and C. transversalis) and fourth instars. The consumption rates of pea aphids by the larvae increased with stage, but with a decline in the later part of the fourth instars, just prior to pupation. Adult females of early age groups (between 2 and 7 days) had higher consumption rates than later age groups in all the four species. Further in adult females, consumption rates decrease with increase in age, but without significant changes in conversion efficiencies and relative growth rates.     

Intraguild predation of the aphid pathogenic fungus Pandora neoaphidis by the invasive coccinellid Harmonia axyridis

Abstract.  1. The ladybird Harmonia axyridis is an invasive alien species in many countries and is predicted to have a negative impact on native biodiversity. However, little is known on the status of this aphidophage as an intraguild predator of natural enemies of aphids such as insect-pathogenic fungi.
2. The study assessed the predation of the aphid-specific pathogenic fungus Pandora neoaphidis by adult and larval H. axyridis collected from the U.K. (an invasive population) and Japan (a native population) relative to that of the ladybird Coccinella septempunctata (native to the U.K.) and the non-U.K. C. septempunctata subspecies brucki that were either starved or unstarved.
3. Overall, predation of uninfected aphids was greater than infected aphids and, when given a choice, a preference for aphids was shown. However, the extent of this preference was dependent on the species and origin of the coccinellid. Harmonia axyridis (U.K.) consumed the greatest quantity of fungal cadavers and showed little preference for uninfected aphids over infected aphids. In contrast, C. septempunctata rarely consumed infected aphids. Life stage had no direct effects on predation but starved coccinellids consumed more uninfected aphids than infected aphids.
4.  Harmonia axyridis (U.K.) is a stronger intraguild predator of P. neoaphidis cadavers than the native species C. septempunctata and, therefore, may have an impact on the occurrence and persistence of P. neoaphidis . The differences in intraguild predation by H. axyridis collected in the U.K. and those from Japan suggests that individuals that invaded the U.K. could have a different genetic profile to those in its native range.     

Relationships Between Attack and Escape Rates, Cannibalism, and Intraguild Predation in Larvae of Two Predatory Ladybirds

We compared incidences of cannibalism and intraguild (IG) predation (IGP) and quantified attack and escape rates—mechanisms which possibly account for the difference in incidences of these interactions—in laboratory experiments with Harmonia axyridis and Coccinella septempunctata. There was a tendency for H. axyridis to act as an IG predator and C. septempunctata as an IG prey. Cannibalism was also often observed in both species. The incidences of both IGP and cannibalism were different between the species. The average attack rates of C. septempunctata were less than 20%, but those of the more aggressive H. axyridis exceeded 50%. Larvae of both species attacked conspecifics and heterospecifics H. axyridis larvae successfully escaped when attacked by both conspecifics and by heterospecifics, while larvae of C. septempunctata escaped from attacks of conspecifics but not from those of heterospecifics. Thus the aggressive behavior of H. axyridis, in particular, of the third and fourth instars, negatively affects the larval survival of C. septempunctata. It may contribute to the dominance of H. axyridis in ladybird assemblages and its displacement of other ladybird species in several places in the world.