Axyridis Adults Research Articles

Functional and Numerical Responses of Harmonia axyridis (Coleoptera: Coccinellidae) to Rhopalosiphum nymphaeae (Hemiptera: Aphididae) and Their Potential for Biological Control.

The water lily aphid (Rhopalosiphum nymphaeae) is a highly polyphagous herbivore that causes severe damage to many terrestrial and aquatic plants, especially lotus. Due to environmental concerns about water pollution and other issues caused by chemical control methods, there is an urgent need to develop effective and sustainable control methods. The harlequin ladybird (Harmonia axyridis) is a well-known aphid predator and may pose a potential threat to R. nymphaeae. To study the predation ability of H. axyridis at different developmental stages on R. nymphaeae, we assessed the functional response, attack rate, and search effect of H. axyridis larvae and adults preying on R. nymphaeae. The numerical response of this process was also evaluated under a constant ladybird-to-aphid ratio and constant aphid density conditions, respectively. Our results showed that all predator stages exhibited type II functional responses. The predation rate of individual H. axyridis on R. nymphaeae nymphs significantly increased as prey density increased. In contrast, the search effect of H. axyridis gradually decreased with an increase in prey density. Meanwhile, H. axyridis at different developmental stages possess varying predation abilities; fourth instar and adult H. axyridis were found to be highly efficient predators of R. nymphaeae. H. axyridis adults exhibited the highest predation ability and predation rate, while both the adult and fourth-instar larvae exhibited the highest attack rate. Moreover, fourth-instar larvae exhibited the highest search effect value at initially lower prey densities, although adults surpassed them at higher prey densities. Our results also indicated that H. axyridis exhibited varying degrees of intraspecific interference and self-interference influence as predator density increases. These results strongly support H. axyridis as an effective biocontrol agent for R. nymphaeae.

Design and evaluate the performance of a mechanical system for the release of Harmonia axyridis adults.

Harmonia axyridis (H. axyridis) is the natural enemy of many aphid species. Traditional manual release of H. axyridis adults requires substantial manpower, and release efficiency is low. Automatic mechanical devices can improve the efficiency of delivery. Based on H. axyridis adults' morphological size, a prototype release system for H. axyridis was designed, which considered the adhesion characteristics of H. axyridis adults. According to the measured physical characteristics of H. axyridis adults, the structural parameters of the mechanical system for the release of the H. axyridis adults were determined. The relationship of the quantity of release, the impeller rotating speed, and the time for the release of H. axyridis adults were constructed. The mechanism can quantitatively adjust the number of H. axyridis adults to meet a certain H. axyridis-aphids ratio. Combining the image processing technology with the camera function of a mobile phone, the maximum cross-sectional area method was used to count the H. axyridis adults in the designated area. Results showed that the impeller rotating speed had a significant effect on the survival rate of the H. axyridis adults. When the airflow velocities were 29.5 m/s and 38.3 m/s, the survival rates of the H. axyridis adults were 93.8% and 94.5% at 4.2 rpm. The adhesion rate of the H. axyridis adults was 2.5%-4.6%. This work will provide technical support for the research of biological control.

Cnidium monnieri (L.) Cusson Flower as a Supplementary Food Promoting the Development and Reproduction of Ladybeetles Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae).

Predaceous ladybeetles are highly polyphagous predators that ingest supplementary food from flowering plants. Flowering plants widely grown in agroecosystems can sustain multiple natural enemies of agricultural pests, and the pollen and nectar resources from flowering plants may have a positive role in natural enemies. Cnidium monnieri (L.) Cusson, an annual herb with many flowers, blooms from May to July. C. monnieri can support several predatory natural enemies, and the addition of C. monnieri strips increases the density of Harmonia axyridis (Pallas) and improves the biological control of apple aphids in an apple orchard. H. axyridis is also the most important natural enemy in wheat aphid biocontrol and is attracted to healthy and aphid-infested C. monnieri plants. In addition, adult Propylaea japonica Thunberg survives significantly longer on C. monnieri flowers than on a water-only diet. In this study, a laboratory experiment was conducted to assess (i) the effect of nutritional supplements derived from C. monnieri flowers on the development and reproduction of H. axyridis under a wheat aphids-only diet; (ii) the effect of C. monnieri flowers on H. axyridis adult reproduction performance. We compared the larval durations, survival, weight, adult longevity, and reproduction of H. axyridis reared on wheat aphids-only and aphids plus C. monnieri flower diets. The results showed that H. axyridis larvae reared on aphids plus flowers had significantly greater weights and survival rates, shorter larval durations, and produced 1.62 times more eggs than those reared on wheat aphids-only diets. H. axyridis adults ingesting a C. monnieri flowers plus an aphid diet increased egg production 1.44 times compared to the aphids-only diet. Our study demonstrates that C. monnieri flowers as a supplementary food positively affect the survival, development, and reproduction performance of H. axyridis.

Ecological function of key volatiles in Vitex negundo infested by Aphis gossypii.

Herbivore induced plant volatiles (HIPVs) are key components of plant-herbivorous-natural enemies communications. Indeed, plants respond to herbivores feeding by releasing HIPVs to attract natural enemies. The present study analyses the effect of HIPVs of Vitex negundo (Lamiaceae), an indigenous plant species in northern China, on the predatory ladybug species Harmonia axyridis. Y-tube olfactometer bioassay showed that H. axyridis adults were significantly attracted by V. negundo infested by the aphid Aphis gossypii. We analyzed and compared volatile profiles between healthy and A. gossypii infested V. negundo, screened out the candidate active HIPVs mediated by A. gossypii which could attract H. axyridis, and tested the olfactory behavior of the candidate active compounds on H. axyridis. The gas chromatography-mass spectrometry analysis showed that five volatile compounds were significantly up-regulated after V. negundo infestation by A. gossypii, and five substances were significantly down-regulated in the terpenoid biosynthesis pathway. The olfactory behavior response showed that H. axyridis has significant preference for sclareol, eucalyptol, nonanal and α-terpineol, indicating that this chemical compounds are the important volatiles released by V. negundo to attract H. axyridis. This study preliminarily clarified that V. negundo release HIPVs to attract natural enemies when infected by herbivorous insects. The description of the volatile emission profile enriches the theoretical system of insect-induced volatile-mediated plant defense function of woody plants. Applications in crop protection would lie in designing original strategies to naturally control aphids in orchards.

Direct and indirect effects of banker plants on population establishment of Harmonia axyridis and aphid control on pepper crop.

Banker plant systems increase biological pest control by supporting populations of natural enemies, i.e., using non-pest arthropod species as alternative prey. However, the presence of alternative prey does not always result in improved control of the target pest species owing to the complexity of biotic interactions. To increase the effectiveness of banker plants in IPM programs, a fine understanding of the indirect interactions between target aphid and alternative prey mediated by biocontrol agents is necessary. In this study, we first established a banker plant system, banker plant (Vicia faba)-alternative prey (Megoura japonica)-predator (Harmonia axyridis), to control the target pest (Myzus persicae) on pepper. We found that M. japonica strongly preferred faba bean as a host plant and posed no risk to Solanaceous crops. Harmonia axyridis adults had no significant predation preference for the alternative prey. In the short term, the interaction direction of the two aphid species depended on the relative initial density and the timescale. Harmonia axyridis showed a stronger negative effect on M. persicae than that on M. japonica. In the long term, the presence of alternative prey, M. japonica, enhanced the control effect of H. axyridis to M. persicae with initial density of 100-500 aphids per plant. The presence of the alternative prey could proliferate the population of H. axyridis, with from 0.2- to 2.1-fold increase of H. axyridis eggs. Overall, we put forward a strategy for setting the initial density of alternative prey of the banker plant system to target the high and low density of aphids, which highlighted the importance of indirect interactions in designing a proper banker plant system.

Effects of long-term cold storage on maternal and progeny fitness of laboratory-reared Harmonia axyridis adults

Effects of long-term cold storage on maternal and progeny fitness of laboratory-reared Harmonia axyridis adults

Transgenerational Effects of a Neonicotinoid and a Novel Sulfoximine Insecticide on the Harlequin Ladybird.

Simple SummaryThe coccinellid Harmonia axyridis is an important natural enemy of various agricultural pests, including aphids. Agrochemicals can negatively affect the performance of arthropod natural enemies and, thus, the ecological services they provide. In this context, we assessed the lethal and sublethal effects of two neuroactive compounds with different chemical structures: the long-established neonicotinoid insecticide, imidacloprid, and the novel, sulfoximine insecticide, sulfoxaflor, both of which act on nicotinic acetylcholine receptors against adult and developmental stages of H. axyridis. Estimated LC20 and LC50 doses of imidacloprid for a target pest species, Aphis gossypii, resulted in significantly greater mortality in contact bioassays against adult H. axyridis compared with equivalent LC20 and LC50 doses of sulfoxaflor. Both concentrations of imidacloprid and sulfoxaflor significantly reduced the proportion of ovipositing females of parental generation. LC20 and LC50 dose of imidacloprid and LC50 dose of sulfoxaflor significantly reduced both the fecundity and fertility of parental generation. In progeny of parents exposed to both insecticides at LC50 concentrations the juvenile survival rate was significantly reduced, and both concentrations of imidacloprid and sulfoxaflor, except LC20 dose of sulfoxaflor, significantly prolonged the larval development time. These experimental results disclose the negative influence of sulfoxaflor and imidacloprid at low concentrations on the harlequin ladybird and its subsequent generation. Hence, actions should be taken to optimize imidacloprid and sulfoxaflor applications for the control of aphid pests, aiming at preserving the biocontrol services provided by this important predator.The harlequin ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), is a generalist predator and an effective biocontrol agent of various insect pests that has been exploited for the control of aphid pests in the greenhouse and field. However, insecticides are widely used to control aphid pests worldwide and the potential non-target effects of sulfoxaflor and imidacloprid for controlling aphid pests towards this biocontrol agent are little known. Although both sulfoxaflor and imidacloprid act on nicotinic acetylcholine receptors of insects, sulfoxaflor has a novel chemical structure compared with neonicotinoids. We assessed the lethal, sublethal and transgenerational effects of sulfoxaflor and imidacloprid on H. axyridis simultaneously exposed via ingestion of contaminated prey and via residual contact on the host plant at LC20 and LC50 doses estimated for the cotton aphid. Imidacloprid significantly reduced the survival of H. axyridis adults compared to sulfoxaflor at the same lethal concentration against cotton aphid. Both concentrations of imidacloprid and sulfoxaflor reduced the proportion of ovipositing females, and both concentrations of imidacloprid and sulfoxaflor, except LC20 dose of sulfoxaflor, reduced the fecundity and fertility of the parental generation. In the progeny of imidacloprid- and sulfoxaflor-exposed parents, both tested LC50 concentrations significantly decreased the juvenile survival rate, and both concentrations of imidacloprid and sulfoxaflor, except LC20 dose of sulfoxaflor, prolonged the development time. Our findings provide evidence of the negative influence of imidacloprid and sulfoxaflor at low lethal concentrations on the harlequin ladybird and on the progeny of exposed individuals, i.e., transgenerational effects. Hence, these findings stress the importance of optimizing the applications of imidacloprid and sulfoxaflor for the control of aphid pests, aiming at preserving the biocontrol services provided by H. axyridis throughout the integrated pest management approach.

Functional response of Harmonia axyridis preying on Acyrthosiphon pisum nymphs: the\xa0effect of temperature

In the current study, we investigated the functional response of Harmonia axyridis adults and larvae foraging on Acyrthosiphon pisum nymphs at temperatures between 15 and 35 °C. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of the functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to A. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instar H. axyridis consumed the most aphids. For fourth instar larvae and female H. axyridis adults, the successful attack rates were 0.23 ± 0.014 h−1 and 0.25 ± 0.015 h−1; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

Connection between cuticular hydrocarbons and melanization in Harmonia axyridis revealed by RNAi-mediated silencing of the CYP4G79

The insect cuticle is a multifunctional shield providing shape stabilization and threat protection. It has a complex composition of cuticular components. Although cuticular melanization is essential and melanin spots are common for many insects, information about the connection between melanization and other cuticular components is limited. The ladybird Harmonia axyridis adults and pupae exhibit regular and predictable melanin spots on their cuticles. Here, RNAi-mediated silencing of CYP4G79 , which functions as an oxidative decarbonylase in hydrocarbon biosynthesis, decreased the cuticular hydrocarbon contents at different levels of H. axyridis , resulted in enlarging (mild) or breaking (severe) melanin spots on cuticle. In addition, transcriptional analysis showed key genes of cuticular melanization up-regulated under CYP4G79 RNAi; Scanning electron microscope (SEM) and Oil Red O (ORO)-staining results suggested a distribution correlation among Cuticular hydrocarbons (CHCs), lipids and melanin. For severe phenotypes with broken melanin spots of treated beetle’s pupal cuticle, histological examinations showed that abnormal pigmentation in cuticular layers were physiologically caused by cuticular microstructural change. In brief, these two cuticular components of H. axyridis , may function together; and cuticular hydrocarbons are essential to the formation of melanin spots. Furthermore, the orderly formations of cuticular components are important to cuticle construction; this study furthers our understanding of insect cuticle formation and functions.

Phototactic Behavior of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is a well-known aphid predator in its native Asian habitat. Currently, H. axyridis are predominantly released for aphid control in China; however, light traps and colored sticky cards also were widely used to control aphid pests, which results in population reduction of H. axyridis. This study used 15 monochromatic and whole-spectrum lights to investigate whether H. axyridis has a particular light intensity and spectral preference. Positive phototaxis was found in both H. axyridis adults and larvae to a broad specturm of light. The phototactic responses of adult H. axyridis showed significant similarity to that of larvae. Female H. axyridis had four sensitivity maxima at 414, 492, 504, and 568 nm, male H. axyridis had four maxima of sensitivity at 380, 492, 504, and 549 nm, and H. axyridis larvae also had four maxima of sensitivity at 414, 504, 549, and 568 nm. The phototactic responses of H. axyridis to various monochromatic lights did not significantly differ between sexes. The larval response to a broad spectrum of light was significantly less than that of adults. Furthermore, H. axyridis adults of both sexes showed an increased phototactic response at low intensities and a decreased response at high intensities for both blue light and green light. Moreover, the phototactic response of both female and male H. axyridis was strongest at 10 lux. The males of H. axyridis are more sensitive to light intensity than females; however, the H. axyridis light intensity experiments between sexes showed no significant differences. These behavioral differences could be exploited for the development of selected colored light traps used for insect pest management.

Effect of different diets on the growth and development of Harmonia axyridis (Pallas)

AbstractHarmonia axyridis (Pallas) is an important natural enemy of crop pests. Feeding H. axyridis through artificial diets (ADs) is an important means to achieve large‐scale production. In this study, the effects of different diets on the growth, development and reproduction of H. axyridis were comprehensively evaluated, and the reasons for the reduced reproductive capacity of H. axyridis fed ADs were preliminarily explored. Artificial diets were prepared using pig liver and pork as the main ingredients. Larval duration, larval survival rate, egg production and other traits were comprehensively evaluated. Harmonia axyridis fed ADs during both the larval and adult periods completed growth and development from larva to adult but had a prolonged development duration (6.13‐day extension) and reduced survival rate (15.3% reduction) in the larval stage. In addition, adults could not lay eggs. Next, individuals of H. axyridis were fed Megoura japonica (Matsumura) in the larval stage and an AD, adequate aphids (AA) or an artificial diet plus 5 (AD5), 10 (AD10) or 25 (AD25) aphids in the adult stage. The adults in the AD group produced a small number of eggs (103.3 eggs). When aphids were added to the diet, egg production gradually increased with the number of aphids added. The AD25 group exhibited no significant difference in egg production compared with that in the AA group (983.8 eggs and 1,158.3 eggs, respectively). Anatomical observations of the H. axyridis adults in these five groups revealed that ovary development was slowest in the AD group. In addition, we found that the levels of vitellogenin and juvenile hormone were significantly lower in the AD group than in the AA group. These results provide a foundation for formulating ADs for H. axyridis and improving the large‐scale reproduction of this species.

Antennal sensory organs and glands of the harlequin ladybird, Harmonia axyridis

AbstractHarmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is a sub‐cosmopolitan species. Native to Asia, it has been released during the 20th century for classical and augmentative biological control of several herbivorous insects, mostly aphids and coccids. Despite its recognized positive impact on biological control, H. axyridis is now considered among the most dangerous invasive species in Europe and in most places where it has established. This is mostly due to its ability to reduce the populations of native predatory species of the same trophic guild. When exploring a new area, H. axyridis adults use semiochemical cues to acquire information about the habitat. Presumably, these cues are perceived by the sensilla located on the antennae. Surprisingly, in spite of the huge literature existing on H. axyridis, the antennal sensory organs have been poorly characterized. Here, we used scanning and transmission electron microscopy (SEM, TEM) techniques to study H. axyridis antennae, with focus on the various types of sensilla and their distribution in male and female individuals. The presence of various classes of antennal sensilla belonging to the main types described in insects (chemoreceptors, mechanoreceptors, and thermo‐hygroreceptors) was highlighted, as well as the widespread presence of antennal glands. The investigations showed some peculiar characteristics not known in Coccinellidae, such as the concentration of sensory structures at the level of the distal part of the apical antennomere and the discovery of antennal glands associated with it. No sexual dimorphism was revealed, neither for the general structure of the antenna (similar number of antennomeres and presence of modifications), nor for the total length and width of the antenna, the relative size of the antennomeres, the types of antennal sensilla, of their distribution and abundance. The potential relevance of these sensory structures and antennal glands, reported for the first time in Coccinellidae, is discussed in the context of intra‐ and interspecific communication.

Laboratory Evaluation of the Effect of Insecticides on Chrysoperla carnea (Neuroptera: Chrysopidae), Forficula auricularia (Dermaptera: Forficulidae), Adalia bipunctata (Coleoptera: Coccinellidae) and Harmonia axyridis (Coleoptera: Coccinellidae)

The effect of 8 biopesticides and 23 synthetic pesticides on the eggs and larvae of Chrysoperla carnea (Stephens, 1836), adults of Forficula auricularia Linnaeus, 1758, larvae of Adalia bipunctata (Linnaeus, 1758) and adults of Harmonia axyridis (Pallas, 1773) have been evaluated under laboratory conditions. All of the tested biopesticides were harmless (causing mortality < 30%) or only slightly harmful (causing mortality 30–79%) to the tested natural enemies. The tested synthetic fungicides were harmless or slightly harmful, with the exception of myclobutanil, which was moderately harmful (causing mortality 90–99%) to A. bipunctata larvae. The tested synthetic insecticides were harmless or slightly harmful to C. carnea eggs and F. auricularia larvae. Various results were obtained for neonicotinoids ranging from the harmful effects (causing mortality > 99%) of thiacloprid on A. bipunctata larvae and H. axyridis adults to the harmless effects of acetamiprid on F. auricularia adults and C. carnea eggs. Thiacloprid, dodine and chlorpyrifos-methyl had effects on the behaviour of F. auricularia adults. The results confirmed the selectivity of the tested biopesticides that had no negative effects on the tested natural enemies.

Effect of long-term cold storage on trehalose metabolism of pre-wintering Harmonia axyridis adults and changes in morphological diversity before and after wintering.

Harmonia axyridis is a major bio-control agent of pests in agriculture and forest ecosystems. It is also a globally important invasive insect species. To test whether dark elytra colour is associated with greater cold hardiness, we compared the survival rate of prolonged cold exposure in both yellow and black colour morphs of female and male H. axyridis. We determined the trehalose and glycogen content, trehalase activity, and the dynamics of genes associated with the trehalose metabolic pathway. Yellow forms predominated before winter began, however black forms increased from 11.15 to 30.46% after overwintering. There was no significant difference in trehalose content between the females and males during overwintering. Glycogen content in over-wintering yellow females and black males increased significantly, while it decreased in black females. Soluble trehalase activity increased significantly in all the insects except black females. Membrane-bound trehalase activity increased in black males, and decreased in black females. Trehalose and glycogen content and trehalase activity were regulated by differential expression of TRE and TPS genes. Female beetles weighed more than males and survived in low temperatures for longer periods of time, regardless of elytra colour, suggesting that mass is a stronger predictor of overwintering survival rather than colour morph. Our results provide a guide for comparing cold resistance in insects and a theoretical basis for cold storage of H. axyridis for use as natural enemies of pests in biological control programs.

Attraction of adult Harmonia axyridis to volatiles of the insectary plant Cnidium monnieri

Plant volatiles mediate the interactions within plant-insect communities and influence the distribution and behavior of insects. Natural enemies often utilize the volatiles that released from plants to locate the profitable patches for foraging. The lady beetle Harmonia axyridis (Pallas) is a dominant generalist predator of various pests in agriculture fields, yet little is known about the chemical cues which the predator employs to locate its prey. In this study, we tested the attractiveness of volatiles emanating from healthy and aphid-infested insectary plant Cnidium monnieri (L.) Cuss. to H. axyridis adults in a Y-tube olfactometer. Next, using coupled gas chromatography – electroantennogram detection (GC-EAD) and gas chromatography – mass spectrometry (GC–MS) identified the volatile components which elicited electrophysiological activity in H. axyridis adults. Lastly, Y-tube olfactometer tests in laboratory and field traps were used to verify the effectiveness of the volatile components. In olfactometer trials, H. axyridis adults preferred healthy and aphid-infested plants versus control. In GC–MS and GC-EAD trials, two antenna-active components (1,2-diethylbenzene and p-diethylbenzene) were detected among the volatile blends emanating from healthy and aphid-infested plants; and in ensuing behavioral assays, H. axyridis adults were attracted to two synthetic volatile compounds. Under field conditions, the number of H. axyridis adults as recorded in traps for two synthetic volatile components at three different concentrations (100 mg/ml, 10 mg/ml, and 1 mg/ml) were significantly higher than those for mineral oil (control). These findings could provide an effective means for the cultivation of insectary plants to develop natural enemy attractants and support the biological control in the field.

Asymmetric intraguild predation of Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) on a native Coccinellidae guild

Abstract Harmonia axyridis is an exotic species that can cause serious impacts on native biodiversity in areas where it is introduced to act as a biological control agent. This predator is often involved with intraguild predation, in most cases with aphids predators. Here, we report the results of experiments designed to understand the outcome of the invasion of H. axyridis on native coccinellid aphidophagous guilds using intraguild predation as a theoretical framework. Tests were conducted to determine the interactions between 1st and 4th instars larvae and H. axyridis adults, with Cycloneda sanguinea, Cycloneda pulchella, Eriopis connexa and Hippodamia convergens larvae, as well as eggs predation rate. Two treatments were used: absence and presence of food, Cinara atlantica. The results showed that 1st and 4th instars larvae and H. axyridis adults are able to prey on larvae and eggs of four Coccinellidae species analyzed, and also their own eggs, showing that this exotic species is a dominant predator in this guild of aphidophagous coccinellids. Adding to these results, studies are recommended, especially the monitoring of these species in the field in the long run, reporting their abundance and diversity as well as their behavior and impact within aphidophagous guilds, especially in Coccinellidae species.

Fitness costs of reflex bleeding in the ladybird beetle Harmonia axyridis: the role of parental effects.

Reflex bleeding is an important antipredator defense mechanism in Coccinellidae. We examined the costs of reflex bleeding in larval and adult stages of the ladybird beetle Harmonia axyridis on offspring fitness and reproductive performance through the comparisons between bled and control larvae, reciprocal crosses of bled/control beetles, and early and late clutch phenotypes. Beetles bled during their larval stage spent a longer time in development and weighed less than controls. Egg fertility was reduced for crosses where either one or both parents had been bled during the larval or adult stage. Offspring crosses that included a parent bled during the larval stage suffered fitness costs in development and female body mass, while those bled during the adult stage suffered no transgenerational costs. Males that suffered bleeding during their larval stage accelerated progeny development of nonbled females in early clutches, suggesting a positive transgenerational effect of larval bleeding, while males that did not suffer bleeding accelerated progeny development of bled females in later clutches. As the underlying effects of bleeding on females' offspring in the early clutches were diminished in the late ones, suggesting another transgenerational effect. The strengths of maternal and paternal effects on progeny development of parents bled at the larval stage were higher in earlier clutches. This study suggests that H. axyridis adults are less affected than larvae by the frequent use of the defensive secretions in their stressful habitats.

Search for Nutritional Fitness Traits in a Biological Pest Control Agent Harmonia axyridis Using Comparative Transcriptomics.

Harmonia axyridis is an important natural predator used in the biological control of insect pests. Vitellogenin (Vg) supplementation to artificial diet can improve fecundity of H. axyridis, however, the effects of Vg on physiology of H. axyridis at the molecular level is unclear. This study investigated the effects of Vg on the physiology (digestive enzyme activities) and transcriptome patterns by feeding H. axyridis adults with treatment (artificial diet with Vg supplement) and control (artificial diet supplemented with bovine serum albumin (BSA). The transcriptome sequencing yielded 43.94 Gb of clean data, and 3,946 differentially expressed genes (DEGs) – including 93 upregulated and 3,853 downregulated genes between the treatment and control. Six DEGs related to development and digestive enzyme were chosen for quantitative real-time PCR (qRT-PCR) to validate the accuracy of the RNA-seq results and confirmed that the transcriptome analysis yielded reliable results. The Vg supplement has increased activities of digestive enzymes and related genes expression in H. axyridis. The transcript level of digestive enzyme genes (apolipoprotein D and phosphoenolpyruvate carboxykinase) were much higher in adults fed on diet supplemented with Vg compared with that of the control.

Artificial diet is fruitful pre-storage nutrition for long-term cold storage of laboratory-reared Harmonia axyridis (Pallas) adults

Cold storage of laboratory-reared natural enemy is important for developing feasible biological control program. Harmonia axyridis, a ‘chill intolerant’ insect, is an important biological control agent in Asia. Previous studies related to cold storage of H. axyridis mostly focused on the field-collected adults, while these techniques were not applicable for laboratory-reared individuals. Pre-storage nutrition has been confirmed to be a critical factor that affects cold tolerance of a given species. In this study, Acyrthosiphon pisum-reared newly emerged adults of H. axyridis were provided with artificial diet or A. pisum as pre-storage diet (named Ha-artificial diet and Ha-aphid, respectively) for 4 days, with sex separated. Before storage, the adults were acclimated at 15 °C for another two days. After that, the six-day old unmated adults were stored at 6 °C for 15, 30, 45, and 60 days. After storage, the adults were transferred back to 25 °C and evaluated for fitness. We found that: (1) adult survival decreased with the increasing of days of storage, and Ha-artificial diet had relatively higher survival rate compared to Ha-aphid; (2) weight loss during storage increased with prolonged storage duration, and Ha-artificial diet had significantly lower weight loss compared to Ha-aphid following the four storage periods; (3) both the pre-oviposition period and egg hatch rates were neither affected by pre-storage diet nor storage duration. While at 60 days, Ha-aphid had significantly lower egg hatch rates compared to unstored control; (4) egg production of Ha-artificial diet following 30 days of storage was significantly higher than that at 60 days or that of Ha-aphid at 30 days, but they all did not significantly differ with unstored control. In summary, artificial diet was suitable for serving as pre-storage diet for laboratory-reared H. axyridis adults, and Ha-artificial diet could be stored for at least 30 days without any detrimental effects. Our results highlight the positive effects of artificial diet serving as pre-storage nutrition and might encourage more studies to develop effective storage techniques for predatory natural enemies.

Volatiles from Sophora japonica flowers attract Harmonia axyridis adults (Coleoptera: Coccinellidae)

The multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), is a common generalist predator in China and is occasionally found gathering on the Chinese pagoda tree, Sophora japonica, in summer. In a field investigation, we found that H. axyridis adults preferred S. japonica during its flowering period even though their optimal prey (aphid) is absent at this time. In addition, male and female adults were attracted to S. japonica flowers to a similar extent in a Y-tube olfactometer assay. Using coupled gas chromatography-electroantennogram detection (GC-EAD), we identified a flower odor component (nonanal) that elicited a significant electrophysiological response in H. axyridis. Electroantennogram (EAG) dose-dependent responses revealed that the amplitude of the adult beetle's EAG response increased with increasing concentration of nonanal, peaking at 10 mg mL−1. In Y-tube olfactometer behavioral tests, H. axyridis adults preferred a 10 mg mL−1 nonanal source over a 100 mg mL−1 diluent. Under field conditions, the adults were significantly attracted to both concentrations (10 and 100 mg mL−1), and high concentrations generally had greater attraction. All these results suggest that nonanal, a volatile compound of S. japonica flowers, greatly attracts H. axyridis adults. This study provides a basis for the development of synthetic attractants of H. axyridis, with the potential to promote biocontrol services of this generalist predator in the native area (e.g., China) and to suppress its population by mass trapping in its invasive areas.