Intrinsic advantages of Cheilomenes sexmaculata over two coexisting Coccinella species （Coleoptera：Coccinellidae）

Development, survival and reproductive performance of coexisting ladybird species, viz. Cheilomenes sexmaculata, Coccinella septempunctata, and Coccinella transversalis, of the tribe Coccinellini were studied and compared to assess their coexistence and ecological relationships. High values of life history parameters, viz. developmental rate,immature survival, fecundity, egg viability, reproductive rate and conversion of efficiency of ingested food were recorded for C. sexmaculata followed by C. transversalis and C.septempunctata suggesting that the former has intrinsic advantages over the latter two species. This could possibly counterbalance its disadvantages, like relatively smaller size and weight, thereby making it competitive. The developmental period increased with increase in body size. Exceptionally high fecundity after single mating has been recorded in C. sexmaculata. The egg viability, however, was lower than in both Coccinella species.     

Survival, development and life tables of two congeneric ladybirds in aphidophagous guilds

Two congeneric aphidophagous ladybirds, Coccinella septempunctata and Coccinella transversalis, were reared on three aphid species, Lipaphis erysimi, Myzus persicae and Aphis nerii, to estimate the effect of prey quality and intra- and interspecific interactions on their survival and development of life stages. Mortality of first instar ladybirds of both species was highest feeding on A. nerii. Preimaginal mortafity was lowest when feeding on L. erysimi （C. septempunctata, 1.6% and C. transversalis, 3.2%）, and highest when feeding on A. nerii （ C. septempunctata, 6.2% and C. transversalis, 8.2%）. Comparatively higher weight and larger size of C. septempunctata along with the lower levels of mortality recorded suggested that it is more likely to have acted as an intraguild predator than C. transversalis. High recorded mortality of C. transversalis is attributed to probable intraguild predation on account of its smaller size. The major sources of mortality were probably cannibalism, intraguild predation and other unknown factors. Lower prey quality increased the incidence of cannibalism and intraguild predation, especially in C. transversalis. The investigation suggests an intrinsic competitive advantage for C. septempunctata over C. transversalis in guilds of three aphid species.     

Mating in aphidophagous ladybirds: costs and benefits

Abstract:  Mating costs and benefits were studied in three aphidophagous ladybirds, viz. Cheilomenes sexmaculata , Coccinella septempunctata and Propylea dissecta by subjecting them to different numbers of matings. Longevity, fecundity and percent egg viability were regressed with number of matings to determine the costs and trade-offs, if any. Longevity decreased with increasing number of matings in both C. sexmaculata and P. dissecta indicating a cost of mating. The lack of such a cost in C. septempunctata has been ascribed to spermatophore consumption by females of this ladybird. Both fecundity and percent egg viability increased with increasing number of matings and are probably indicative of the benefits. Short-lived females distributed their reproduction uniformly in their lifetime while long-lived females showed a high burst of reproductive activity followed by a gradual decline. Percent egg viability decreased after the completion of the requisite number of matings.     

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.     

REPRODUCTIVE BEHAVIOUR OF TWO APHIDOPHAGOUS LADYBEETLES, CHEILOMENES SEXMACULATA AND COCCINELLA TRANSVERSALIS

Abstract  Reproductive behaviour of two aphidophagous ladybeetles, Cheilomenes sexmaculata and Coccinella transversalis was studied. A premating period of 5.0±0.5 and 11.7±0.4 days and a pre-oviposition period of 5.5±0.7 and 12.7±0.5 days was observed for C. sexmaculata and C. transversalis , respectively. Males of both the species exhibited courtship in five steps, viz . approach, watch, examine, mount and attempt. Sexually immature, recently mated and ovipositing females rejected male advances in both the species. Chemical, visual and behavioural cues probably play a role in mate recognition. Quiescent mating occurred in C. sexmaculata , whereas abdominal shakings in the form of bouts and strokes were characteristic in C. transversalis. C. sexmaculata had a relatively prolonged mating duration (133.4±z8.9 min) than C. transversalis (37.9±2.0 min), possibly due to the absence of active processes, i.e ., bouts and strokes. The active processes in C. transversalis decreased with multiple matings in a day. Unmated adults of both the species mated more vigorously than the mated ones. Reproductive performance of both the species was best after multiple matings.     

Numerical response of ladybird beetles (Col., Coccinellidae) to aphid prey (Hom., Aphididae) in a field bean in north-east India

Two predaceous species of Coccinellidae, Menochilus sexmaculatus and Coccinella transversalis , occurred abundantly in bean crops infested with the aphid, Aphis craccivora Koch in north-east India. The number of eggs and adults of the two coccinellids increased in response to the increase in the population of aphid prey. Reproductive numerical responses were found to be synchronous to prey density whereas aggregative numerical responses appeared asynchronous in the later part of the aphid cycle on beans. Menochilus sexmaculatus oviposited smaller clusters of eggs at lower density of aphids than C. transversalis which laid larger clusters and showed greater numerical response at higher densities of aphids. Within a species cluster the size of the eggs seems to be directly related to aphid density. The two coccinellid species of this study seem to be efficient predators of A. craccivora in terms of their reproductive and aggregative numerical responses.     

Sibling cannibalism in aphidophagous ladybirds: its impact on sex-dependent development and body weight

Abstract:  The effects of sibling egg cannibalism on sex-dependent development and adult body weight were determined by rearing simultaneously two groups of sibling larvae of ladybirds, viz. Propylea dissecta and Coccinella transversalis individually. The first group included cannibals (i.e. neonates, which took a sibling egg as the first meal and later fed on aphids, Aphis craccivora ) and the other included non-cannibals (reared exclusively on aphids). The cannibal larvae developed faster with heavier adults than non-cannibals. This expedited development and nutritional advantage (increased body weight) was greater in first instars indicating maximum benefit of sibling cannibalism to them. Sibling cannibalism was relatively more advantageous to male than to female ladybirds. Laboratory data predict that the larger size of adults in the field could possibly be the result of sibling egg cannibalism at the neonate level.     

Ovarian dynamics and oosorption in two species of predatory lady beetles (Coleoptera: Coccinellidae)

Abstract Ovarian development and oviposition dynamics of two species of lady beetle, Coccinella septempunctata L. and C. transversoguttata richardsoni Brown, are examined in laboratory experiments in which pea aphids (Acyrthosiphon pisum Harris) are provided ad libitum and then removed. Both species respond to prey removal by stabilizing at lower body weights, and by laying progressively fewer and smaller eggs of reduced viability, until oviposition ceases altogether after several days of starvation. Dissections of females after prey removal reveal similar patterns of oosorption in both species. However, C. septempunctata reduces oviposition more rapidly after prey removal than does C. transversoguttata. When prey are again provided, C. septempunctata soon lay as many eggs as previously but C. transversoguttata lay fewer. Females, especially of C. septempunctata, that stop producing and resorb eggs in the absence of prey lay more eggs subsequently than do females that feed continually on prey provided ad libitum and lay eggs throughout the experiment. Thus, although both species are responsive to a rapid change in prey availability, C. septempunctata appears to be especially responsive. Rapid responses to changes in prey availability may contribute to the greater abundance and reproductive success of this introduced species relative to the native C. transversoguttata in western North American alfalfa fields that exhibit widely varying pea aphid densities. However, both species engage in oosorption as a means of reserving resources under poor prey conditions and enhancing future reproductive effort when prey conditions improve.     

The use of honeydew in foraging for aphids by larvae of the ladybird beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Abstract.  1. To clarify the use of honeydew in foraging for aphids by larvae of the ladybird beetle, Coccinella septempunctata L., searching behaviour of ladybird larvae for Aphis craccivora Koch and Acyrthosiphon pisum Harris and the abundance of honeydew under aphid colonies were examined in laboratory experiments.
2. More larvae responded by climbing the plants with aphids than responded to plants without aphids. When the plants were replaced with sticks, in order to exclude visual and olfactory cues from plants and aphids, more larvae of C. septempunctata climbed sticks above the area that contained honeydew than climbed sticks above the area that did not contain honeydew. Then, ladybird larvae use honeydew as a contact kairomone when foraging for aphids.
3.  Aphis craccivora deposited a larger number of honeydew droplets beneath the plants than did similar numbers of A. pisum. Thus, C. septempunctata larvae licked more frequently the honeydew of A. craccivora than that of A. pisum and spent longer searching on the area containing honeydew of A. craccivora than that of A. pisum . Consequently, a larger number of larvae climbed a stick above honeydew of A. craccivora than that of A. pisum.
4. It may be also considered that C. septempunctata larvae can distinguish honeydew of the two aphid species and respond more strongly to A. craccivora than A. pisum.     

Voracity and feeding preferences of two aphidophagous coccinellids on Aphis citricola and Tetranychus urticae

Voracity and feeding preferences of adult Coccinella septempunctata L. and Harmonia axyridis Pallas (Coleoptera: Coccinellidae, tribe Coccinellini) were evaluated in the laboratory on a common prey, the spirea aphid, Aphis citricola van der Goot (Homoptera: Aphididae), and on the twospotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), a prey previously unrecorded for these two predators. The experiments were carried out in the laboratory on apple saplings (Malus domestica Borkhausen). Adult males and females of H. axyridis consumed significantly more mites than adults of C. septempunctata. For H. axyridis, males consumed 41.3 spider mites in 24 h and females 48.4, whereas for C. septempunctata males consumed 14.1 prey and females 15.2. The consumption of spirea aphids by the males was similar for the two species. Consumption by the females was significantly greater for H. axyridis (46.5) than for C. septempunctata (22.2). The two coccinellids showed a significant preference for A. citricola in the presence of T. urticae. This preference was more pronounced for C. septempunctata. The total number of prey consumed and the percentage of exploited biomass decreased significantly for C. septempunctata and stayed relatively constant for H. axyridis as the number of mites increased in the prey ratio. Our results suggest that T. urticae is only an alternative prey for both predators, and that H. axyridis should be more efficient than C. septempunctata in a prey assemblage with aphids and mites.     

Influence of prey species on immature survival, development, predation and reproduction of Coccinella transversalis Fabricius (Col., Coccinellidae)

Six aphid species, viz. Aphis craccivora, Aphis gossypii, Aphis nerii, Myzus persicae, Lipaphis erysimi and Uroleucon compositae were provided as prey to the feeding stages of Coccinella transversalis (Fabricius). All of them were found to be essential prey, however the relative prey suitability varied. All the predatory stages of C. transversalis consumed and preferred A. gossypii, the most and A. nerii, the least. Significant effect of prey quality was observed on pre‐imaginal developmental periods, wet weights and adult longevity. The complete development was shortest on A. gossypii (13.01 ± 0.18 days) and longest on A. nerii (20.51 ± 0.25 days). The total prey consumption by larva, adult male and female in their lifetime was maximum (665.30 ± 5.75, 4831.10 ± 123.54 and 5412.30 ± 94.51, respectively) on A. gossypii and minimum (434.80 ± 4.03, 802.80 ± 34.37 and 905.20 ± 52.48, respectively) on A. nerii. Immature survival, growth index and adult emergence of C. transversalis was maximum (68.33, 7.82 and 88.21%, respectively) when larval instars consumed A. gossypii and minimum (37.75, 2.18 and 60.69%, respectively) after feeding on A. nerii. Female reproduction was also prey quality dependent showing maximum reproductive performance in terms of fecundity and percentage viability, with a highest reproductive period and lowest non‐reproductive period on A. gossypii, followed by A. craccivora, L. erysimi, M. persicae, U. compositae and A. nerii. Regression analysis revealed a positive correlation between: (1) daily prey consumption and relative growth rate, (2) adult weight and developmental rate, (3) weights of adult male and female, and (4) female longevity and fecundity.     

多食性瓢虫捕食5种蚜虫的统计学比较:实验室研究(英文)

通过食蚜瓢虫Propylea dissecta(Mulsant)的捕食统计学参数的比较,尝试回答瓢虫是如何克服食物基础季节性的变动问题。在实验室中饲养五世代的瓢虫从五种蚜虫(Rhopalosiphum maidis(Fitch),Aphis craccivora Kock,Aphis gossypii Glover,Uroleucon compositae(Theobald)和Lipaphis erysimi(Kalt))为食物来源获得营养。相对适合的猎物次序是A.gossypii,A.craccivora,R.maidis,U.compositae和L.erysimi。新生幼虫的死亡率最高,其次是卵。统计表明,净生殖率、内懔增长率和有限增长率为(407.18,0.2274天-1,1.2553天-1)最高的在A.gossypii和最低的(176.02,0.1533天-1,1.1657天-1)在L.erysimi,一个世代时间最短的26.43天是捕食A.gossypii;而最长的33.73天为捕食L.erysimi。本研究为P.dissecta捕食A.gossypii高发生提供一种解释,因为它经历了高内懔增长率和统计参数最佳值。     

Role of surface chemicals in egg cannibalism and intraguild predation by neonates of two aphidophagous ladybirds, Propylea dissecta and Coccinella transversalis

Abstract:  The role of surface chemicals in egg cannibalism and intraguild predation by neonates of two aphidophagous ladybirds, Propylea dissecta and Coccinella transversalis were examined. Neonates of both species prefer to eat non-sibling conspecific eggs than heterospecific eggs, with higher preference in P. dissecta . Surface chemicals appear to play a major role for the preference of conspecific eggs, as the ladybird behaviour was reversed when these chemicals were interchanged. The surface chemicals present on the eggs possibly act as feeding stimulants to conspecific neonates but not for heterospecific neonates. Egg clustering enhances the effect of surface chemical and stimulate non-sibling egg cannibalism and appears to reduce intraguild predation. Egg clustering is advantageous to ladybirds, as it can stimulate non-sibling cannibalism by neonates. It appears that aggregation of chemicals present on the conspecific egg surface possibly attracts the hungry conspecific neonate, providing the first meal for its survival, while protecting against heterospecific predators. Neonates of both ladybirds were reluctant to eat heterospecific eggs.     

七星瓢虫成虫对烟蚜的捕食作用

对七星瓢虫CoccinellaseptempunctataL .成虫对烟蚜Myzuspersicae的捕食作用进行了定量研究。七星瓢虫成虫对烟蚜的功能反应属HollingⅡ型反应 ,拟合的圆盘方程为Na =1 .1 5 76Nt ( 1 +0 .0 0 3 48Nt) ,χ2 检验表明圆盘方程理论值与实测值相符。捕食选择试验表明在烟蚜、烟青虫Helicoverpaassaut(Guenee)卵和 1龄幼虫 3种猎物中 ,七星瓢虫成虫最喜好烟蚜。七星瓢虫成虫对自身密度的功能反应用Watt模型拟合为A =2 90 .0 3P-0 .7584,其捕食作用率与个体间相互干扰作用的关系用Hassell模型拟合为E =0 .8783 7P-0 .1 0 0 94。文中进一步就烟田中七星瓢虫的保护利用进行了讨论。     

Predatory effect of Coccinella septempunctata on Thrips tabaci and Trialeurodes vaporariorum

Abstract:  The predatory effect of adult ladybird Coccinella septempunctata L. on adults of thrips, Thrips tabaci Lindeman, and whiteflies, Trialeurodes vaporariorum (Westwood), was examined in controlled environment chambers, on tomato leaves, in transparent small plastic cages at proportions of 1/(10 + 10), 1/(20 + 20), 1/(30 + 30) and 1/(40 + 40) predator/number of thrips and whiteflies. We conclude that C. septempunctata could be used with success for the biological control of thrips and whiteflies in greenhouse crops, with almost the same effectiveness as for aphids, at predator/prey proportions near 1 : 30. Additionally, it was found a prey preference for T. tabaci in comparison with T. vaporariorum . According to the model used, effective predation is correlated with predator/prey ratio rather than to prey preference.     

温度和光周期影响两种同域发生瓢虫同种和异种组合时的猎物消耗量和利用率（英文）

【目的】印度次大陆是世界上最脆弱的地理景观。气候条件的略微变动可能对其季节周期可能产生不良影响,并引起农业生态系统中蚜虫的大暴发。七星瓢虫Coccinella septempunctata L.和狭臀瓢虫C.transversalis Fab.是该次大陆上广泛分布、同域发生的两种食蚜性瓢虫。【方法】设计异地试验,来探究同种和/或异种组合时的这两种瓢虫用共同的猎物资源(豌豆蚜)饲养时,对增加的温度(15,20,25,30和35℃)和光周期(8L∶16D,12L∶12D和16L∶8D)的响应。【结果】结果表明,在这5个不同温度和3个不同光周期条件下,同种或异种组合时这两种瓢虫表现出了拮抗作用。尽管表现出拮抗作用,但是同种或异种组合的两捕食动物在25℃和长光周期(16L∶8D)条件下消耗、转化和利用的猎物生物量最大。然而,它们的猎物消耗率、转化效率和生长速率在异种组合中最高。在5个不同温度下,4龄幼虫均更有效地利用猎物生物量,将其转变成自身生物量,而雌成虫在3个不同光周期条件下也是如此。【结论】因此可以推断,增加的温度和光周期条件可能不会阻止同种和异种组合中的瓢虫发生拮抗作用,但是在25℃和长光周期(16L∶8D)条件下,相互作用的瓢虫的猎物消耗量和利用率为最佳。     

干扰作用及空间异质性对七星瓢虫成虫捕食作用的影响

通过系统研究,得出：1)七星瓢虫Coccinella septempunctata雌雄成虫在捕食过程中麦秆数越多,环境阻力越大,捕食作用率越低;2)七星瓢虫与异色瓢虫 Harmonis axyridis 捕食过程中的种间干扰作用大于两种瓢虫的种内干扰作用;3)异色瓢虫(♀)种内竞争强度I与瓢虫数P的关系为I=0.0012+1.4072lgP;异色瓢虫(♂)种内竞争强度I与P的关系为I=0.0058+1.3942lgP;七星瓢虫(♀)种内竞争强度I与P的关系为I=-0.0072+0.7234lgP。异色瓢虫(♀)和七星瓢虫(♀)的种间竞争强度I与天敌数量(P)关系的模型为I=0.0539+1.1167 lgP,异色瓢虫(♀)和七星瓢虫(♂)的种间竞争强度I与P的模型为I=0.0018+1.1944lgP。     

饥饿对七星瓢虫捕食作用的影响

通过不同饥饿程度七星瓢虫雌、雄成虫对麦二叉蚜捕食作用的研究,得出：①饥饿不能改变七星瓢虫雌、雄成虫捕食作用的功能反应类型;②七星瓢虫雌、雄成虫间在各种饥饿条件下的捕食量差异均不显著;③七星瓢虫雌、雄成虫对麦二叉蚜的捕食量（Ｎａ）随着时间（ｔ）的变化,其模型分别是Ｎａ＝９０／１＋ｅ０．９４５３４－０．１５７４５ｔ和Ｎａ＝９０／１＋ｅ０．８７２８５－０．１２９８５ｔ;④七星瓢虫雌、雄成虫之间在２４ｈ内的捕食速度（Ｖ）差异不显著,其与时间段（ｘ）关系的模型分别为Ｖ＝８．３５５９ｘ－１．２４６０和Ｖ＝４．３４８７ｘ－０．５９６４。     

COMPARATIVE DEMOGRAPHICS OF A GENERALIST PREDATORY LADYBIRD ON FIVE APHID PREY: A LABORATORY STUDY

Abstract  Prey driven demographic parameters of an aphidophagous ladybird, Propylea dissecta (Mulsant) were studied in attempt to answer how ladybird overcomes the problem of seasonally fluctuating food base. The ladybird reared for five generations in laboratory derived differential nutrition from five food sources ( i.e . aphid species, Rhopalosiphum maidis (Fitch), Aphis craccivora Koch, Aphis gossypii Glover, Uroleucon compositae (Theobald) and Lipaphis erysimi (Kalt.)). The order of relative prey suitability was A. gossypii, A. craccivora, R. maidis, U. compositae and L. erysimi . Neonates suffered maximum mortality followed by eggs. Estimates of net reproductive rate, intrinsic rate of increase and finite rate of increase were highest (407. 18, 0.2274 day^-1, 1.2553 day^-1) on A. gossypii and lowest (176.02, 0.1533 day^-1, 1.1657 day^-1) on L. erysirni . Generation time was shortest (26.43 days) on A. gossypii and longest (33.73 days) on L. erysirni . The present study thus, provides an explanation to the high incidence of P. dissecta on A. gossypii , as it experienced high intrinsic rate of increase and optimal values for related demographic parameters.     

Optimal number of matings in two aphidophagous ladybirds

Abstract.  1. The present study was designed to identify the optimal number of matings required for maximum fecundity and egg viability in two aphidophagous ladybirds, Cheilomenes sexmaculata and Propylea dissecta .
2. For this purpose, ladybirds were subjected to different numbers of matings and the reproductive responses were recorded thereafter.
3. The Gompertz model was used to draw asymptotic graphs for fecundity and per cent egg viability in both ladybird species. Ninety-five per cent and 50% of maximum theoretical fecundity and per cent egg viability were predicted from the model.
4. Ninety-five per cent maximum theoretical fecundity was obtained after 13.25 and 12.95 matings in C. sexmaculata and P. dissecta , respectively; and 8.95 and 11.25 matings were required for 95% maximum theoretical per cent egg viability in C. sexmaculata and P. dissecta , respectively.
5. The results of these experiments clearly support the existence of an optimal number of matings in these two ladybird species leading to maximum adult fitness.