Diversity in warning coloration is easily recognized by avian predators

Warning coloration is a widespread strategy to alert predators about prey unprofitability. The success of this strategy partly depends on predators being able to learn and recognize certain signals as indicators of toxicity, and theory predicts that this is easier if signals converge on similar colours. However, the diversity in warning signal form is astonishing, contradicting predictions. Here, we quantified ladybird signal diversity with respect to avian vision, measuring how unique and discernible each signal is from one another. In addition, we measured signal conspicuousness against a series of backgrounds, namely an average green, average brown, and where we collected each species, to determine whether signals are more contrasting against the ladybirds’ local substrates than compared to average ones. This allowed us to establish whether there are local adaptations in conspicuousness that promote signal diversity. We found that while ladybird signals are unique and recognizable, specialist species are more contrasting against the background they are most commonly found on. However, overall our study suggests that warning signals have evolved to be effective against a wide range of natural backgrounds, partly explaining the success of this strategy in nature.     

Mating rates and the prevalence of male‐killing Spiroplasma in Harmonia axyridis (Coleoptera: Coccinellidae)

Maternally inherited bacteria that kill male but not female hosts during embryogenesis have been widely reported in invertebrates. Harmonia axyridis is one of the species infected by male‐killing Spiroplasma. The presence of male‐killers in host populations can lead to the occurrence of extremely female‐biased sex ratios. Furthermore, infected females may have fewer chances to mate if males can discriminate between infected and uninfected females and prefer the latter. Although there have been many investigations of male‐killer infection rates in H. axyridis, little is known about the influence of host mating on male‐killer infection dynamics. We investigated copulation rates and changes in infection frequency in a wild population of H. axyridis in western Japan. Almost all infected females collected each year laid fertilized eggs and had therefore mated. Mean infection rates of females collected each year were 13% in 2003, 15% in 2012 and 23% in 2013. Statistical analysis showed that neither the copulation rate nor the infection rate differed significantly among years. These results suggest that the infection rate of H. axyridis with male‐killing Spiroplasma is kept approximately constant and that there is no difference in the chance of mating with infected and uninfected females.     

Influence of intraguild predation between Episyrphus balteatus and Hippodamia variegata on their prey

Intraguild predation (IGP) is an interaction that frequently occurs in natural enemy communities, especially aphidophagous predators. This research investigated IGP intensity between Episyrphus balteatus De Geer (Diptera: Syrphidae), with Hippodamia variegata Goeze (Coleoptera: Coccinellidae). Five predator combinations including second and third larvae of H. variegata and third instar larvae of E. balteatus plus control treatment (totally six treatments) were tested. The effect of IGP on cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) population density was investigated on sweet pepper seedlings under laboratory microcosms. In most combinations, the third instar larvae of E. balteatus alone reduced an A. gossypii population more efficiently than ladybird larvae and their combinations. Furthermore, IGP between third instar of E. balteatus and second larvae of H. variegata was asymmetrical; second instar H. variegata larvae were always the intraguild prey for third instar E. balteatus. The obtained result showed that outcome of IGP interaction on cotton aphid density was non-additive.     

三峡库区典型小流域农业非点源氮磷流失特征

基于2007-2009年的野外观测数据对戴家沟小流域降雨径流与农业非点源氮磷流失的时间序列变化关系及其特征进行研究.结果表明:2007-2009年,戴家沟小流域降雨量和径流量峰值变化一致,二者相关系数为0.904.总氮和总磷浓度变化趋势吻合,但总氮对降雨径流变化响应的灵敏度高于总磷;氮流失浓度受降雨径流变化影响显著,而磷流失则表现出逐年递增的趋势;氮磷比的变化特征与总氮浓度的变化特征一致,且与径流波动有良好的耦合关系.2007-2009年,戴家沟小流域降雨径流量累积百分比峰值出现时刻与总氮、总磷流失量累积百分比峰值出现时刻不吻合,表明流域农业非点源污染具有较大的随机性和分散性,二者没有严格的对应关系.     

Models of clines in sexual selection by female choice

Most models of sexual selection by female choice have considered discrete, homogenous populations. This paper studies the evolution of a female preference along a cline in the frequency of a preferred male trait. Single alleles control both the preference and preferred character.
Fisher's process initially causes the preference to spread to some 'maximum' frequency with a corresponding rise in character gene frequency. At this stage, the cline in preference does not necessarily mirror that of the trait. Then, however, preference frequency usually decreases, albeit very slowly, and the preference cline always comes to mirror that of the preferred character. Eventually, preference is completely lost from the cline and the character cline decays to that seen under random mating. This loss can only be prevented if the preference is initially frequent enough to push the character to fixation throughout the cline.
Consequently, a preference that arises after the preferred trait may increase very little in frequency itself and have a negligible effect on trait frequency before being lost from the population. Special conditions, such as cyclical natural selection, may be necessary to explain the spread of a preference in a cline from a low initial frequency to frequencies as high as those observed. A preference that predates the preferred trait can enter the population at a high frequency and radically alter a cline in the frequency of a preferred male trait, albeit often transiently.     

棉田捕食性瓢虫控害功能的分析

在系统调查棉田捕食性飘虫种数量动态的基础上,应用生态能学的方法,分析并比较了不同插种期、套间作等农业措施对棉田捕食性飘虫控害虫功能的影响。结果表明,不同类型棉田飘虫对害虫的摄入量为26．45－70kJ.m^-2,分别占整个捕食性在天敌摄入量的28．30％－47．88％,是棉田捕食性天敌的优势种类;不同类型棉田飘虫对棉蚜的控害系数为5．07％－12．85％,并随着棉花播种期的推后和间套作呈现出下降趋势,它们在棉田生态系统害虫生态调控中发挥着重要作用。     

Host-Specific Myrmecophily and Myrmecophagy in the Tropical Coccinellid Diomus thoracicus in French Guiana

A variety of arthropods, particularly insects, have developed myrmecophilous interactions with ants to gain access to resources and/or for protection. Among these myrmecophiles, only a few examples have been documented in the Coccinellidae, most of them involving species able to feed on ant-tended Hemiptera. We report here a new case of obligate myrmecophily in the coccinellid Diomus thoracicus. Larvae are invariably and exclusively found in the nests of the ant Wasmannia auropunctata and seem to rely on ant brood as their only food source. Not only do ant workers show no aggressiveness toward the D. thoracicus larvae in their behavioral interactions at the colonial level, but also at the species level; while coccinellid adults are always attacked. The integration of the larvae inside of the ant nests is based on their chemical mimicry of the host's cuticular cues. Therefore, given the presence of the D. thoracicus larvae inside of the ant's nest, their predation on Wasmannia brood and their chemical mimicry, this species can be considered a specific parasite of W. auropunctata. Overall, this new case of myrmecophily not only specifically involves a highly invasive ant species, but also provides insights into the evolution of myrmecophily and myrmecophagy in coccinellids.     

DOES THE VOLATILE HYDROCARBON PROFILE DIFFER BETWEEN THE SEXES: A CASE STUDY ON FIVE APHIDOPHAGOUS LADYBIRDS

Insect hydrocarbons (HCs) primarily serve as a waterproofing cuticular layer and function extensively in chemical communication by facilitating species, sex, and colony recognition. In this study, headspace solid‐phase microextraction is employed for investigating the sex‐specific volatile HC profile of five ladybirds collected from Lucknow, India namely, Coccinella septempunctata (L.), Coccinella transversalis (Fabr.), Menochilus sexmaculatus (Fabr.), Propylea dissecta (Mulsant), and Anegleis cardoni (Weise) for the first time. Major compounds reported in C. septempunctata, C. transversalis, and A. cardoni are methyl‐branched saturated HCs, whereas in M. sexmaculatus, and P. dissecta, they are unsaturated HCs. Other than A. cardoni, both the sexes of the other four ladybirds had similar compounds at highest peak but with statistically significant differences. However, in A. cardoni, which is a beetle with a narrow niche, the major compound in both male and female was different. The difference in volatile HC profile of the sexes of the five ladybirds indicates that gender‐specific differences primarily exist due to quantitative differences in chemicals with only very few chemicals being unique to a gender. This variation in semiochemicals might have a role in behavioral or ecological aspects of the studied ladybirds.     

Use of prey and non-prey food by the ladybird beetle Eriopis connexa (Coleoptera: Coccinellidae) under laboratory-rearing conditions

Prey for predators can fluctuate in abundance and in quality over time requiring predator strategies to cope with food shortage. Coccinellinae are often associated with sap-sucking pests that exhibit high population unpredictability such as aphids and psyllids. Eriopis connexa (Germar) (Coleoptera: Coccinellidae) is a predator with potential for biological control, especially a well-studied population which is resistant to pyrethroids used to control insect defoliators. Both larvae and adult E. connexa were provided ad libitum prey and non-prey foods (pollen and honey water solution) at increasing intervals from 1 to 10 days. Neonate larvae of E. connexa required eating prey daily to develop into adults. However, non-prey food such as honey water solution did prolong larval and adult survival but neither fulfilled larval development nor adult reproduction. Honey water solution promoted 100% adult survival up to 25 days in the adult stage without prey with oviposition returning after daily feeding on prey. Females subjected to increased feeding intervals over four days reduced oviposition and lived longer, but 10-day feeding intervals correlated with risk to adult survival. These results indicate the importance of non-food sources in E. connexa maintenance and the ability of larvae and adult females to compensate for prey scarcity.     

Mating refusal and its significance in females of the ladybird beetle, Harmonia axyridis

ABSTRACT. . Mating receptivity in females of the ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was studied with reference to internal and environmental conditions. Females sometimes reject copulation: they run away, or shake off the male and bend the abdomen upwards. Newly emerged females show a greater likelihood of accepting copulation with an advance in the stage of ovarian development, this being related to age. Females usually mate repeatedly, but frequently show refusal behaviour under unfavourable food conditions. Dissections reveal that females which accept copulation have a greater number of mature eggs in the ovary than do rejectors. Results also suggest that the food conditions are a major environmental factor, directly controlling mating receptivity.     

释放天敌瓢虫和施用化学农药吡虫啉对麦田蚜虫的控制效果评价

以常规防治农药甲胺磷做对照,比较高效低毒化学农药吡虫啉和天敌昆虫瓢虫对田间麦蚜的防治效果。结果表明,施用10%吡虫啉可湿性粉剂300ghm2药后5d和10d的防效分别为15.1%和31.1%,对麦蚜防效理想。释放天敌昆虫瓢虫后5d和10d的防效分别为-347.6%和-171.7%,防效差,这是由于释放天敌后的强降雨所致。     

Effect of parental ageing on offspring developmental and survival attributes in an aphidophagous ladybird,Cheilomenes sexmaculata

The present study is the first attempt to investigate the effect of parental ageing of Cheilomenes sexmaculata (Fabricius) on total developmental period, developmental rate, adult weight on emergence, longevity, egg to adult survival and age‐specific survivorship of the offspring. Young parents (10–20 day old) produced offspring with the shortest total developmental period, highest development rate, highest weight on emergence, greater longevity and highest survival. Age‐specific survivorship of the offspring of younger parents declined later than the offspring of middle (30–40 day old) and old (50–60 day old) aged parents. This study would help in understanding the effect of parental ageing on future generations of predaceous ladybird beetles and would be helpful in designing mass multiplication programme of the bioagent, C. sexmaculata, in the laboratory.     

Prey quality dependent growth,development and reproduction of a biocontrol agent,Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae)

Growth, development and reproduction of a ladybird beetle, Cheilomenes sexmaculata (Fabricius) were investigated in relation to seven aphid species, viz. Aphis craccivora Koch, Aphis gossypii Glover, Rhopalosiphum maidis (Fitch), Myzus persicae (Sulzer), Uroleucon compositae (Theobald), Lipaphis erysimi (Kaltenbach) and Aphis nerii Boyer de Fonscolombe on specific hosts. Maximum prey consumption, percent larval survival, developmental rate, weight of different life stages, percent adult emergence, adult longevity and fecundity of C. sexmaculata were recorded on A. craccivora, and minimum on A. nerii. A linear relationship was found between development rate and weight of adult, daily prey consumption and relative growth rate, log weights of adult males and females, and female longevity and total fecundity. On the basis of overall performance of ladybird the order of suitability of prey species was A. craccivora>A. gossypii>R. maidis>M. persicae>U. compositae>L. erysimi>A. nerii.     

Egg dumping by predatory insects

Synovigenic insects resorb oocytes when food is scarce and mature oocytes when food is plentiful. These two antagonistic processes allow an optimal allocation of resources to reproduction and somatic functions. Unlike hymenopteran parasitoids, ladybirds cannot resorb mature oocytes present in the oviducts. Is the energy contained in these oocytes lost or is there a mechanism for recovering it when needed? Females of two species of ladybird beetles Adalia bipunctata (L.) and Adalia decempunctata (L.) that are starved for >24 h lay single infertile eggs, which they immediately eat, and these eggs comprise the mature oocytes in the oviducts at the onset of starvation. This behaviour has some similarities to egg dumping reported in herbivorous insects and is part, in ladybird beetles, of a process to retrieve energy invested in reproduction. Such behaviour may exist in other predatory synovigenic insects species that do not invest in maternal care.     

Dropping behaviour of larvae of aphidophagous ladybirds and its effects on incidence of intraguild predation: interactions between the intraguild prey, Adalia bipunctata (L.) and Coccinella septempunctata (L.), and the intraguild predator, Harmonia axyridis Pallas

Abstract.  1. Two experiments were performed in the laboratory to assess the behaviour of dropping from a host plant as a defence against intraguild predation in aphidophagous ladybird larvae.
2. In the first experiment, encounters were observed on bean plants between fourth instars of the intraguild predator species, Harmonia axyridis , and first instars of two other ladybird species, Adalia bipunctata (L.) and Coccinella septempunctata (L.). The percentages of first instars of the latter two species that dropped from the plant in response to attack differed dramatically, with 47.5% of C. septempunctata first instars dropping vs. 0% of A. bipunctata .
3. In the second experiment, first instars of A. bipunctata or C. septempunctata and a fourth instar of H. axyridis were allowed to forage together on bean plants for 3 h. During this time, 44.3% of C. septempunctata larvae dropped from the plant, but less than 2% of A. bipunctata larvae did so. In contrast, 95.0% of A. bipunctata larvae fell victim to intraguild predation by H. axyridis vs. only 54.5% of C. septempunctata larvae.
4. The significance of dropping behaviour of ladybird larvae as a defence against intraguild predation, and the relationship of dropping behaviour to species-specific habitat affinity of ladybirds, is discussed.     

Laboratory evaluation of certain natural compounds against the melon ladybird beetle,Epilachna chrysomelina F. attacking cucurbit plants

Neem Azal-T/S, Neudosan and Spruzit flüssig at different concentrations were evaluated against the second and fourth instar larvae of E. chrysomelina under laboratory conditions. In case of acute effects, the highest mortality was recorded when larvae were offered squash leaves treated with the highest concentration (2%) of Neem Azal-T/S, and the lowest mortality was, however recorded after treating them with the lowest concentration (0.25%). On the other hand, the second instar larvae were more susceptible to any compound at any concentration than the fourth instar one. One per cent Neudosan formulation showed the highest toxicity to both the 2nd and 4th instar larvae. As the concentration of this compound decreased the mortality percentage of treated larvae decreased to reach the minimum at the lowest concentration (0.25%). The same trend could be applied for Spruzit flüssig compound. When Neem Azal-T/S was compared with Neudosan, the later at any concentration was more toxic than the former. Generally, Neudosan and Spruzit flüssig seemed to be active against E. chrysomelina during the first three days after treatment, then, deterioration occurred among this compound. In case of latent effects, the duration of the treated fourth instar larvae of E. chrysomelina with any tested compound, was prolonged. An increase in the concentration caused prolongation of this period to reach the longest at the highest concentration. This prolongation, was more pronounced after Neem Azal-T/S treatment followed by Neudosan and Spruzit flüssig. The same trend could be applied for the duration of the pupal stage as being affected by the different concentrations of the tested compounds which were applied to the fourth instar larvae. However, adults of E. Chrysomelina treated as fourth instar larvae with high concentrations of Neem Azal-T/S showed some adult malformations. The sex ratios of adults produced from fourth instar larvae treated with different concentrations of the tested natural compounds were about 1?:?1, except for two cases; 1% Neudosan where the number of females were double the number of males and 0.5% Spruzit flüssig where the number of males were double the number of females. An increase in the concentration of any tested compound caused an obvious decrease in the percentage of emerged adults. The least emergence percentage was recorded in the case of Spruzit flüssig, followed by Neudosan and Neem Azal-T/S. Treating the fourth instar larvae with the different concentrations of the tested natural compounds significantly shortened the longevity of produced adults and decreased the fecundity.     

七星瓢虫对麦长管蚜捕食作用及其模拟模型的研究

实验室内16—21℃的温度下,七星瓢虫雌成虫捕食行为集中在8:00—22:00。瓢虫各龄幼虫及雌成虫对麦长管蚜的功能反应均属Holling Ⅱ型。28℃时,瓢虫雌成虫的攻击率最大,处理时间最短。随温度增加,攻击率减小,处理时间增加。假设:猎物种群在无捕食者存在时,呈Logistic曲线增长;捕食者随机搜寻猎物。对猎物的功能反应为Holling Ⅱ型,捕食者个体间存在相互干扰;捕食者种群存在一个最低死亡率K_0,随种群增大,死亡率增加,增加速率与密度成反比;捕食者取食的猎物转化为自身部分的比例为β。 七星瓢虫-麦长管蚜捕食作用系统模拟模型:较好地描述了当麦长管蚜种群增长到某一数量时,放置一头瓢虫雌成虫后蚜虫种群增长过程。本文对模型平衡点作了局部稳定性分析。     

Performance of Cryptolaemus montrouzieri feeding on Pulvinaria aurantii ovisacs on citrus plants

We studied the performance of the coccinellid Cryptolaemus montrouzieri on citrus plant species infested with orange pulvinaria scale, Pulvinaria aurantii, under controlled conditions in the laboratory. The experimental host plants were blood orange, grapefruit, lemon, pummelo and kumquat. All life history parameters indicated best performance of C. montrouzieri, when reared on P. aurantii ovisacs on the leaves of grapefruit. Pummelo, blood orange, lemon or kumquat were less suitable.