Harmonia Axyridis Research Articles

A roadmap for ladybird conservation and recovery.

Ladybirds (Coleoptera: Coccinellidae) provide services that are critical to food production, and they fulfill an ecological role as a food source for predators. The richness, abundance, and distribution of ladybirds, however, are compromised by many anthropogenic threats. Meanwhile, a lack of knowledge of the conservation status of most species and the factors driving their population dynamics hinders the development and implementation of conservation strategies for ladybirds. We conducted a review of the literature on the ecology, diversity, and conservation of ladybirds to identify their key ecological threats. Ladybird populations are most affected by climate factors, landscape composition, and biological invasions. We suggest mitigating actions for ladybird conservation and recovery. Short-term actions include citizen science programs and education, protective measures for habitat recovery and threatened species, prevention of the introduction of non-native species, and the maintenance and restoration of natural areas and landscape heterogeneity. Mid-term actions involve the analysis of data from monitoring programs and insect collections to disentangle the effect of different threats to ladybird populations, understand habitat use by taxa on which there is limited knowledge, and quantify temporal trends of abundance, diversity, and biomass along a management-intensity gradient. Long-term actions include the development of a worldwide monitoring program based on standardized sampling to fill data gaps, increase explanatory power, streamline analyses, and facilitate global collaborations.

Plant volatile compound methyl benzoate is highly effective against Spodoptera frugiperda and safe to non-target organisms as an eco-friendly botanical-insecticide

Recent studies have indicated that the plant volatile methyl benzoate (MB) exhibits significant insecticidal bioactivity against several common insects. However, the potential environmental hazards of MB and its safety to non-target organisms is poorly understood. In the present study, these characteristics were investigated through laboratory experiments and field investigations. The results revealed that MB was highly toxic to the agricultural pest, fall armyworm Spodoptera frugiperda. Compared with the commercial pesticide lambda-cyhalothrin, the toxicities of MB against S. frugiperda larvae and adults were comparable and 3.41 times higher, respectively. Behavioral bioassays showed that the percentage repellency of MB to S. frugiperda larvae was 56.72 %, and MB induced 69.40 % oviposition deterrence rate in S. frugiperda female adults. Furthermore, in terms of median lethal concentration (LC50) and median lethal doses (LD50), MB exhibited non-toxic effects on non-target animals with 3-d LC50 of > 1 % to natural predators (Coccinella septempunctata and Harmonia axyridis), 3-d LD50 of 467.86 µg/bee to the bumblebee Bombus terrestris, 14-d LC50 of 971.09 mg/kg to the earthworm Eisenia fetida, and 4-d LC50 of 47.30 mg/L to the zebrafish Brachydanio rerio. The accumulation of MB in the soil and earthworms was found to be extremely limited. Our comparative study clearly demonstrated that MB is effective as a selective botanical pesticide against S. frugiperda and it is safe to use in the tested environment, with no toxic effects on non-target animals and natural predators.

A comparison of microbiota in the ladybird Harmonia axyridis between native and invaded ranges

AbstractAs a biocontrol agent of aphids and coccids, the harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was introduced from its native Asian range into North America. There, it has spread quickly and widely, potentially contributing to the decline of endemic ladybirds. This study examined microbial communities residing in H. axyridis in its native and introduced or invaded regions. We collected ladybirds at 11 localities across mainland China (native range) and at seven localities across the USA (invaded range) and applied next‐generation amplicon sequencing to examine microbial communities. We found that the diversity of the microbial community of H. axyridis in the invaded range declined compared to the native range. The microbial community differed markedly in composition between native and invaded ranges. Among all identified 22047 amplicon sequence variants, only 4.2% were shared by the two ranges, whereas 4967 were unique to the invaded and 16159 to the native range. Our findings suggest that the composition of the microbial community of H. axyridis is largely restructured in the invaded North American region compared to the native Asian region.

Effect of temperature on the life cycle of Harmonia axyridis (Pallas), and its predation rate on the Spodoptera litura (Fabricius) eggs

Biological control is one of the strategies of pest control which is determined by the biological fitness and metabolic rates of the predator species used. Temperature and resource are important factors which influence the role of insects as biocontrol agents. Harmonia axyridis is a cosmopolitan and non-specific polyphagous predator. It can survive ecologically diverse environments and exploit multiple preys. This study investigated the effects of temperature on the population parameters of H. axyridis and its predation on the eggs of prey Spodoptera litura. For this purpose, an age–stage, two-sex life table of the predator was constructed at four constant temperatures, i.e. 15, 20, 25 and 30 °C, under laboratory settings of: 70 ± 5% RH, and 16:8 h (L: D) photoperiod. A computer simulation was then used to project the population and predation responses with respect to temperatures tested. We found that the development of larvae and adult (male/female) stages of H. axyridis decreased with colder temperatures (i.e., 15 and 20 °C) but increased with warmer temperatures (25 and 30 °C). The intrinsic rate of increase (r) and mean generation time (T) were 0.0662 d−1 and 79.84 d at 15 °C, 0.0843 d−1 and 64.90 d at 20 °C, 0.1067 d−1 and 48.89 d at 25 °C, and 0.1378 d−1 and 35.55 d at 30 °C, respectively. The mean duration of the total pre-adult stage was 44.26, 32.91, 20.63, and 15.39 d at 15, 20, 25, and 30 °C, respectively. At 30 °C. the finite rate of increase (1.1477 d−1) was the highest and the mean generation time (35.55 d) was the shortest. The net predation rate (C0) was 7935.54, 10,466.28, 10,139.38, and 7126.36 eggs at 15, 20, 25, and 30 °C, respectively. Population and predation projections were proportional to temperature. These findings are important for modelling the population responses of H. axyridis to climate change and tailoring integrated pest management strategies to altered climates.

Intercropping flowering plants facilitate conservation, movement and biocontrol performance of predators in insecticide-free apple orchard

Habitat management is an important approach suppressing pest via conservation biological control in agricultural systems. Intercropping flowering plants is a well- practiced habitat management measure, supporting predators with shelter, nectar, alternative prey and pollen. However, few studies systematically revealed predator’s conservation performance, transfer process and biocontrol ability by intercropping flowering plants in apple orchards. Here, an experimental model of intercropping flowering plants in apple orchard was planned for two consecutive years to response above questions. Four flowering plants conserve a different number and proportions of six main predator species (three ladybeetles (Propylaea japonica, Harmonia axyridis and Hippodamia variegata), one lacewing (Chrysoperla sinica), one hoverfly (Episyrphus balteatus) and one spider (Misumenops tricuspidatus)). By rubidium (Rb) marking technique, transfer rate of predators C. sinica from flowering plant Cnidium monnieri to apple trees were 79.5 % and 84.1 % in 2020 and 2021, respectively. Transfer rate of predators H. axyridis from flowering plant C. monnieri to apple trees were 74.2 % and 80.1 % in 2020 and 2021, respectively. By predator exclusion trials, the Biocontrol Services Index (BSI) was calculated in sampling date, in which the number of aphids on the caged and uncaged branch has significant difference in the four flowering plants and untreated control plots in 2020 and 2021, respectively. Thus, our results suggest that, intercropping flowering plants in insecticide-free apple orchard contributed to increase the number of predators and biological control of aphid Aphis spiraecola. These findings support that intercropping flowering plants as a promising management option could be implemented in apple orchards.

Density and seasonal dynamics of Bemisia tabaci and its predators in different agricultural landscapes in South China.

Bemisia tabaci is the main pest of agriculture in many regions of the world. The resistance of whitefly to pesticides has increased as a consequence of the continuous irrational use of wide-spectrum pesticides. Thus, pesticides are no longer always effective as a long-term control method. The agricultural landscape can affect the occurrence of an insect population. The objective of this study was to clarify the occurrence of whitefly and its predators in tomato fields in different agricultural landscapes. Different landscapes are classified into urban, flower, water, and mountain landscapes by the principal component analysis method. In 2018–2019, whitefly had the longest main activity period and the lowest density in the flower landscape. The water landscape helped to maintain the highest densities of whitefly during the main activity period. Nine species of predators were sampled, and Nesidiocoris tenuis, Chrysoperla sinica, Menochilus sexmaculata, and Harmonia axyridis were the dominant species throughout the sampling season in both years. During the main activity period, N. tenuis had the highest density in all sampled landscapes. The density of the dominant predators was the highest in the flower landscape, and each natural predator had the largest temporal niche width in the 2-year sampling period. Bemisia tabaci, N. tenuis, and M. sexmaculata were highly synchronized temporally. The flower landscape showed satisfactory results in suppressing whitefly. Increasing the proportion of flowering plants and increasing the diversity of plant crops in the agricultural landscape can effectively reduce the densities of whitefly during an outbreak.

Analysis of the bacterial communities of four predatory natural enemies collected from a Northern China Bt cotton field

• 16 s RNA sequencing was used to study microbial diversity of four natural enemies. • Harmonia axyridis and Propylaea japonica have the highest microbial diversity. • There are three similar dominant phyla in H. axyridis and P. japonica . • They have 11 common dominant symbiotic bacteria. Predatory natural enemies are major insect species in cotton field ecosystems. Microbes that live inside these insects play essential roles in vital host activities, however, the microbiota of these insects have not been well characterized. In this study, we used Illumina 16S rRNA amplicon sequencing to investigate microbial diversity of the natural enemies Chrysoperla sinica, Harmonia axyridis , Propylaea japonica and Orius similis from a cotton field in northern China. The microbial diversity of C. sinica was low and its dominant bacterial community were Rickettsia (87.78%) and Wolbachia (6.29%). The microbial community of O. similis was more diverse than that of C. sinica . The microbial diversity of H. axyridis and P. japonica was higher, and they had similar dominant phyla, which included Firmicutes, Proteobacteria and Bacteroidetes. Their common dominant bacterial community were Romboutsia , Escherichia-Shigella , Bacteroides , Terrisporobacter , Enterobacter , Lactobacillus , Fusobacterium , Actinobacillus , Sphaerochaeta , Bacteroidales_S24-7_group and Cyanobacteria. This study also forms the basis for further study on the microbiota of natural enemies from different habitats.

Melanin Synthesis Pathway Interruption: CRISPR/Cas9-mediated Knockout of dopa decarboxylase (DDC) in Harmonia axyridis (Coleoptera: Coccinellidae).

CRISPR/Cas9 technology is a very powerful genome editing tool and has been used in many insect species for functional genomics studies through targeted gene mutagenesis. Here, we successfully established CRISPR/Cas9 research platform in Asian multi-colored ladybird beetle, Harmonia axyridis, an important natural enemy in biological control. In this study, one pivotal gene dopa decarboxylase (DDC) in melanin synthesis was targeted by CRISPR/Cas9 to generate mutants in H. axyridis by CRISPR/Cas9 technology. Our results showed that injection of single guide RNA of the DDC and Cas9 protein into preblastoderm eggs induced one insertion and four deletion (indels) mutant H. axyridis. Mutations of HaDDC gene generated 25% mutant rate with melanin missing phenotype in larva, pupa,l and adult stage. The predation ability of the fourth instar larvae has no significant difference between wild (control) and mutant H. axyridis (G0), while these mutant fourth instar larvae had longer developmental period than that of the wild type. Consequently, the total predation of the fourth instar larvae was significantly increased in H. axyridis mutants comparing with the wild type. These results indicated that the success of CRISPR/Cas9 gene editing in H. axyridis. The gene editing platform in H. axyridis would facilitate the gene function research and promote special strain of predatory ladybird beetle generation.

Toxicity and risk assessment of nine pesticides on nontarget natural predator Harmonia axyridis (Coleoptera: Coccinellidae).

Harmonia axyridis (Coleoptera: Coccinellidae) is a beneficial predatory arthropod in the agricultural ecosystem. For the success and development of integrated pest management strategies, it is essential to assess the toxicity risks of commonly used pesticides to nontarget arthropods. The glass tube residue method was used to determine the risk of nine pesticides to H. axyridis after second-instar exposure. To assess the potential risk of the selected pesticides, the pre-adult LR50 values were calculated by the hazard quotient (HQ) method. The LR50 (application rate causing 50% mortality) values of imidacloprid, dinotefuran, thiamethoxam, acetamiprid, bifenthrin, and dimethoate were 0.44, 0.82, 0.10, 0.05, 0.04, and 0.21 g a.i.ha-1 , respectively, showing unacceptable risk to H. axyridis after exposure to in and off field. However, emamectin benzoate and two fungicides, tebuconazole and myclobutanil, posed a low risk to H. axyridis and their HQ values were less than the trigger value of 5. The four neonicotinoid insecticides (imidacloprid, dinotefuran, thiamethoxam, and acetamiprid), pyrethroid bifenthrin, and organophosphorus dimethoate showed a high risk to H. axyridis. Emamectin benzoate, tebuconazole, and myclobutanil showed a low risk to H. axyridis under both exposure scenarios. The results provide critical scientific evidence to guide future regulation of pesticide management practices and protection of nontarget arthropods like H. axyridis. © 2022 Society of Chemical Industry.

Establishment and Expansion of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in Urban Green Areas in the Iberian Peninsula: From 2015 to 2021.

Simple SummaryHarmonia axyridis (Coleoptera: Coccinellidae) is a widespread invasive ladybird. In this study, we determine its occurrence and expansion in urban areas of the Iberian Peninsula after 2014. We also define the aphidophagous ladybird species complex in urban areas of the northeastern Iberian Peninsula and track any changes between 2015 and 2021. The expansion of the species mainly occurred in Catalonia (northeast Iberian Peninsula), where spring and summer populations on trees and shrubs and overwintering aggregations were recorded. The records of H. axyridis populations allow us to distinguish between two areas: one that has already been invaded and another that has not yet been invaded. The relative abundance of the ladybird species in each area is determined on a yearly basis. In the invaded area, H. axyridis became dominant two years after its detection, replacing Adalia bipunctata. This change in species prevalence is more pronounced in trees highly infested with aphids. In the not yet invaded area, changes in species dominance also occurred, and A. bipunctata replaced Oenopia conglobata from 2020 onwards. The yearly release of this ladybird in urban green areas for aphid control purposes could explain this shift. This study defines the current situation of H. axyridis in the Iberian Peninsula, and determines the main changes in ladybird species assemblages during the last few years.In the Western Palearctic region, Harmonia axyridis (Coleoptera: Coccinellidae) is mainly established in urban areas. In this study, we update its occurrence in urban areas of the Iberian Peninsula and determine its expansion after 2014. Changes in the ladybird species assemblage are also evaluated. We compile information about the records of H. axyridis in Spain from 2015 to 2021. In addition, we sample different locations to determine the relative abundances of the species composing the aphidophagous ladybird complex. The expansion of H. axyridis mainly occurred in Catalonia (Iberian Peninsula), where it is possible to identify two clear areas: one that has already been invaded and another that has not yet been invaded. Harmonia axyridis became the dominant species in the invaded area two years after it was first identified. This dominance is clearly shown on Liriodendron tulipifera and Tilia platyphyllos, where it accounted for more than 75% of the total collected individuals in the last year of the study. In the not-yet invaded area, Adalia bipunctata overcame Oenopia conglobata and became the prevalent species from 2020 onwards, likely due to its regular releases for aphid biocontrol. This study reveals that changes in ladybird species assemblages may not only be caused by invasive species, but also by biological control practices.

Toxicity of Photorhabdus luminescens and Xenorhabdus bovienii bacterial metabolites to pecan aphids (Hemiptera: Aphididae) and the lady beetle Harmonia axyridis (Coleoptera: Coccinellidae)

Toxicity of the metabolites of two bacteria, Photorhabdus luminescens and Xenorhabdus bovienii, symbionts of entomopathogenic nematodes, were tested in the laboratory against the multicolored Asian lady beetle, Harmonia axyridis, the black pecan aphid, Melanocallis caryaefoliae, and the blackmargined aphid, Monellia caryella. Bacterial broth prepared from both P. luminescens and X. bovienii demonstrated high levels of toxicity equivalent to the pyrethroid insecticide bifenthrin and caused higher insect mortality than tryptic soy broth plus yeast extract (TSY) (blank control) against M. caryella; broth culture of P. luminescens was more effective than TSY against M. caryaefoliae. At the levels tested, the metabolites were not toxic to H. axyridis.

Changes in the Physiological Adaptation and Regulation Ability in Harmonia axyridis under Chlorpyrifos and Imidacloprid Stress

As the dominant natural enemy of aphids, Harmonia axyridis plays a crucial role in integrated pest control (IPM) in agro-ecosystems. In order to study the physiological adaptation and regulation ability of Harmonia axyridis to insecticides under chemical pesticide stress, ladybirds were treated with organophosphorus chlorpyrifos (chlorpyrifos) and new nicotine imidacloprid (imidacloprid) to explore the physiological adaptability of ladybirds under chemical pesticide stress by activating trehalose metabolism. The results showed that the imidacloprid affect the larvae develop to pupate, resulted in the H. axyridis died and significantly increased the food consumption of Harmonia axyridis, while the chlorpyrifos prolong the development period of pupae significantly and decreased significantly the food intake of H. axyridis fed with aphids treated with chlorpyrifos. It was further found that Chlorpyrifos could inhibit the activity of the trehalase, while the trehalase activity increased under imidacloprid stress, but both insecticides could decrease the trehalose content. The TRE and TPS genes of Harmonia axyridis under chlorpyrifos and imidacloprid stress were upregulated or downregulated. These relevant results can provide a strong reference for the rational use of chemical pesticides or biological pesticides to control pests in the future.

Temporal and climatic variation in the colour forms of Adalia bipunctata and Harmonia axyridis (Coleoptera: Coccinellidae) populations in the United Kingdom

Colour form polymorphism in Adalia bipunctata (Linnaeus, 1785) and Harmonia axyridis (Pallas, 1773) has been extensively studied in the past. Climate, season, and region are known to influence the colour form frequencies of these species, however, this effect is region specific, and the response of populations has changed over time. Here, 5862 photographic records from the UK Ladybird Survey from 2013-2017 were used to assess the geographic variation in colour form frequency (melanic versus non-melanic) of A. bipunctata and H. axyridis across the United Kingdom (UK) in relation to climate and season. Climate data from the UK Met Office were used to determine the effect of climate on melanic form. Seasonal variation in melanic form was observed in H. axyridis but not A. bipunctata. For H. axyridis, the probability of being melanic decreased in areas with higher annual sunlight hours. In A. bipunctata, there was an interaction between sunlight hours and rainfall. In areas with low rainfall, the probability of being melanic was negatively correlated with sunlight hours. Where rainfall was high, the probability of being melanic was positively correlated with sunlight hours. These findings highlight the role of climate in determining the proportion of colour forms in UK populations of A. bipunctata and H. axyridis. Furthermore, the results support the hypothesis that seasonal variation in melanism does not occur in A. bipunctata populations with a low overall proportion of melanics.

Functional Response of Harmonia axyridis to the Larvae of Spodoptera litura: The Combined Effect of Temperatures and Prey Instars.

Functional responses are central to predator–prey dynamics and describe how predation varies with prey abundance. Functional responses often are measured without regard to prey size (i.e., body mass) or the temperature dependence of feeding rates. However, variation in prey size within populations is ubiquitous, and predation rates are often both size and temperature-dependent. Here, we assessed functional responses of larvae and adult Harmonia axyridis on the 1st, 2nd, and 3rd instars of the prey Spodoptera litura across a range of temperatures (i.e., 15, 20, 25, 30, and 35°C). The type and parameters of the functional responses were determined using logistic regression and fitted to the Roger's random predator equation. The magnitude of predation varied with the predator and prey stage, but prey predation increased with warming and predator age. Predation by the female and 4th instar of H. axyridis on the 1st instar of prey was greater, followed by the 2nd and 3rd instar of prey S. litura. No predation occurred on the larger prey for the 1st, 2nd, and 3rd instars of H. axyridis. The larvae and adult H. axyridis produced a type II (hyperbolic) functional response curve across all temperatures and the three prey types they consumed. Space clearance rates, handling time, and maximum predation rates of H. axyridis changed with temperature and prey size, increasing with temperature and decreasing with prey size, suggesting more predation will occur on younger prey. This study indicates an interactive role of temperature and prey/predator size in shaping functional responses, which might complicate the planning of effective biocontrol strategies against this serious pest.

Evaluation of floral-derived volatile blend for attracting aphid parasitoids and lady beetles in the tobacco fields

In tobacco planting in China, the artificial release of aphid parasitoids Aphidius gifuensis has been applied to control aphids for a decade. However, due to seasonal effects and crop rotation, the sustainability of releasing parasitoids and the aphid control efficacy have not been properly evaluated. In this study, effective semiochemical-based attractants were further screened and optimized in the tobacco fields. Film lures were developed to release the synthetic attractant blends. In tobacco planting fields, the synthetic mixture of β-pinene, methyl salicylate, linalool, and limonene(6:6:2:20 mg) significantly increased the population of natural enemies, including A. gifuensis and ladybeetles (Coccinella septempunctata, Harmonia axyridis and Hippodamia variegate) monitored using using malaise traps. The increase in the natural enemy population was related to the season and the lure placement density in the tobacco fields, as well as the distribution of surrounding habitats and flowering plants. A density of 135 lures per hectare significantly increased the number of parasitoids, reduced the population of aphids, elevated the rate of parasitized aphids by 42%, and effectively suppressed the aphid population in the tobacco fields. Combined with the protection of flowering plants around tobacco fields, synthetic lures may provide a technical measure for conservative biological control.

Rising temperatures affect the interspecific interference competition between Harmonia axyridis and Propylea japonica, and their predation rate on Myzus persicae

Rising temperatures affect the interspecific interference competition between Harmonia axyridis and Propylea japonica, and their predation rate on Myzus persicae

Curinus coeruleus1 as Potential Natural Enemy of Diaphorina citri2 in Citrus Orchards at Nuevo Leon, Mexico

Coleopterans Hippodamia convergens Guérin-Méneville, Harmonia axyridis Pallas, Olla v-nigrum Mulsant, Chilocorus cacti L., Chilocorus stigma Say, Cycloneda sanguinea L., Coleomegilla maculate De Geer, and Curinus coeruleus Mulsant were found preying on Diaphorina citri Kuwayama in Nuevo Leon State. C. coeruleus has been reported only in Florida, USA, and at Veracruz, Mexico. This is the first report of the predator at Nuevo Leon, Mexico.

Agriculturally intensified landscapes are associated with reduced body condition of lady beetles

ContextAgricultural intensification is contributing to a global species decline. Underlying mechanisms include toxic effects of pesticides on non-target organisms and reductions in habitat and food availability. However, the effects of agricultural intensification on body condition, particularly of ecosystem service-providing arthropods, are poorly understood.ObjectivesHere, we investigated whether variations in the body condition of common lady beetle species (Coleoptera: Coccinellidae) can be explained by the composition and configuration of the surrounding landscape. Assuming strong seasonal variation in food availability in intensively farmed regions, we included the entire period of lady beetle activity in our study.MethodsLady beetles were collected from April to September 2011 in 30 landscapes in southern Wisconsin, USA. We examined how body size, body density, and lipid content of the beetles responded to the percentage of intensive cropland, habitat diversity, and edge density in the surrounding landscape.ResultsThe strongest predictor of body condition was the percentage of intensive cropland. For every 10% increase in cropland, body density decreased by about 3.9% and lipid content by 6.4%. Landscape diversity and edge density correlated with body condition of individual species.ConclusionsIn agriculturally intensified landscapes, lady beetles with reduced body condition may produce fewer offspring, have lower survival rates, and exert less effective pest control. Thus, our results suggest a mechanistic link between landscape patterns and observed declines in lady beetle populations. Our results also show that the expansion of monocultures affects even common cropland-associated species such as Harmonia axyridis, suggesting a long-term decline in biocontrol services in simplified agricultural landscapes.

Coleoptera claws and trichome interlocking

The present study tests the hypothesis that the specialized claws with a basal tooth found in some coccinellid beetles represent an adaptation to interlock with flexible unbranched trichomes of different plants. We compared the attachment ability of three Coleoptera species, Chnootriba elaterii, Harmonia axyridis (both Coleoptera: Coccinellidae), and Chrysolina herbacea (Coleoptera: Chrysomelidae) with claws of different shape. The attachment ability of insect individuals with or without claws to a plant with leaves bearing straight non-branched trichomes (Cucurbita moschata) and to a plant with smooth leaves (Prunus laurocerasus) was measured in traction force experiments. Insect attachment ability was also tested on a resin replica of C. moschata leaf, to variate trichome stiffness, and on glass as a reference surface. Centrifugal force tester experiments were performed to compare the attachment ability of the two ladybird species to glass and to the leaf of C. moschata. Natural and artificial substrates were characterized in cryo-SEM. The collected data reveal that plant trichomes can enhance insect attachment to plant surface compared with smooth glass by increasing insect friction force, but this is directly related to the trichome stiffness. To effectively grasp soft trichomes, insects evolved special claws-associated structures, such as the dentate claws observed in Coccinellidae.

Effects of aphid-induced semiochemicals from cover plants on Harmonia axyridis (Coleoptera: Coccinellidae).

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an important natural enemy of aphids. Plant species and plant health conditions can affect the behavior of H. axyridis. To determine plant effects on this lady beetle, we examined beetle responses to four cover crops: coriander (Coriadrum sativum L., Apiales: Apiaceae), marigold (Tagetes erecta L., Asterales: Asteraceae), sweet alyssum (Lobularia maritima L., Brassicales: Brassicaceae), and alfalfa (Medicago sativa L., Fabales: Fabaceae). Our goal was to better understand this predator's ovipositional behavior in response to different plants and its olfactory response to the aphid-induced volatiles from these plants. We found that this lady beetle did not have any significant oviposition preference among the four plant species, but H. axyridis preferred to lay eggs on the lower surface of leaves, regardless of the plant species. H. axyridis females had a significant preference for aphid-infested marigolds, but were not attracted by any of the other three cover plants or marigolds without aphid damage. Compared to the uninfested marigold plants, the emission of 12 compounds significantly increased on the aphid-infested marigolds, and two of them were attractive to H. axyridis under suitable concentrations. H. axyridis did not show any significant oviposition preference among the four cover crops. Aphid-infested marigolds can attract H. axyridis. Indole and terpinen-4-ol mediated lady beetle attraction. These synomones have potential for manipulating populations of H. axyridis as a component of conservation biological control. © 2022 Society of Chemical Industry.