Harmonia axyridis is a well-known predatory ladybird beetle renowned for its high degree of elytral pattern polymorphism. The black and yellow-red complementary areas of elytra are respectively attributed to the deposition of melanin and carotenoid pigments, while the carotenoid profiles are likely to be affected by the phenotypic plasticity of dark spots. Here, using a goldenrod-colored mutant (named gr) and a melanic mutant (named ml), we examined their elytral carotenoid profiles and compared them with those of the wild type (named wt). Moreover, we determined whether similar changes could be detected from the newly emerged stage (NE) to the 5-day post-emergence stage (PE5). The results showed that the non-oxidative carotenes accounted for over 95% of the total carotenoid pool in all the three morphs. Moreover, identical composition of carotenes was observed at both stages, with (E/Z)-phytoene and γ-carotene comprising the majority (over 70%). However, distinct profiles of carotenes were detected in ml as compared to wt and gr. Additionally, both ml and gr presented several specific xanthophylls compared to wt. Nevertheless, the three morphs showed similar changes in carotenoid composition from stage NE to PE5, i.e. the proportion of light-colored pigment (colorless (E/Z)-phytoene) decreased, while the proportion of colored pigments (lycopene and γ-carotene) increased. Our findings suggested that while different carotenoid profiles were detected in the two body color mutants, both mutants exhibited a conserved strategy for carotenoid allocation to the elytra during post-emergence development. These findings will contribute to a more comprehensive understanding of the carotenoid-based coloration in insects, particularly its correlation with the melanin-based pigmentation.

As holometabolous insects, ladybird beetles display marked morphological differences between the larval and adult stages. However, the larvae and adults of Chilocorus rubidus share the same diet, and no prior study has compared their mouthparts. In this study, scanning electron microscopy (SEM) was used to examine the ultramorphology of mouthparts and associated sensilla in both adults and larvae of C. rubidus. The results showed that the mouthparts of C. rubidus are of the typical biting-chewing type, and their basic composition of the mouthparts are conserved between larvae and adults. However, the specific morphological characteristics of each mouthpart component varies among different larval instars and between larvae and adults, particularly from the 4th instar to the adult stage. The mandibles of larvae bear bifid incisors, whereas those of adults are unidentate. Additionally, the maxilla and labium exhibit distinct structural differences between the two stages. Six types of sensilla and two types of glandular structures were identified on the adult mouthparts, among which sensilla campaniformia (Sca), sensilla coleconica (Sco), perforated plates (Pp), and cuticular pores (Cp) were absent in the larval stage. The number of all sensillum types gradually increased from the larval to adult stage, especially for the sensory fields on the top of labial palpi and maxillary palpi. In particular, sensilla styloconica II are observed on the tip of labial palpi of ladybird beetles for the first time. These results provide a theoretical basis for understanding the biological control potential of this species.

Many insect species demonstrate thermal-induced phenotypic plasticity in melanin levels as an effective temperature adaptation strategy. Harmonia axyridis (Pallas) (f. succinea morph), known for its diverse elytra patterns, generally displays a reduction in the overall melanin level and spot number on both the dorsal cuticle of pupa and elytra as temperature increases. In our laboratory colony, we have discovered a novel melanism mutant (ml) that exhibits elevated melanin levels throughout most developmental stages compared to the wild type (wt). In this study, we examined whether ml displays similar thermal-induced phenotypic plasticity as wt under different temperatures (17.5°C, 25°C, and 32.5°C). Our findings indicated that ml, inherited in a Mendelian autosomal recessive pattern, exhibited much smaller changes in the occurrence frequency of dark spots on dorsal surfaces of both the pupa and the elytra alongside temperature variations. Additionally, ml consistently had significantly higher melanin levels than wt across all three temperature conditions. Surprisingly, despite having larger dark spot areas on the elytra, ml had higher carotenoid concentrations than wt at 25°C and 32.5°C, while no significant difference was observed at 17.5°C. These results indicated that the melanism mutant ml of H. axyridis displays distinct thermal-induced melanism plasticity compared to the wild type, which will enhance our understanding of the thermal responses of insects differing in genetic background.

Bacteria have a profound influence on life history and reproduction of numerous insects, while the associations between hosts and bacteria are substantially influenced by environmental pressures. Cold storage is crucial for extending the shelf life of insects used as tools for biological control, but mostly causes detrimental effects. In this study, we observed a great decrease in egg hatch rate of cold-stored Harmonia axyridis during the later oviposition periods. Furthermore, most eggs produced by their F1 offspring exhibited complete loss of hatchability. We hypothesized that long-term exposure to cold may greatly alter the bacterial community within the reproductive tracts of H. axyridis, which may be an important factor contributing to the loss of egg viability. Through sequencing of the 16S rRNA gene, we discovered considerable changes in the bacterial structure within the reproductive tracts of female cold-stored beetles (LCS_F) compared to non-stored beetles (Control_F), with a notable increase in unclassified_f_Enterobacteriaceae in LCS_F. Furthermore, in accordance with the change of egg hatchability, we observed a slight variation in the microbial community of eggs produced by cold-stored beetles in early (Egg_E) and later (Egg_L) oviposition periods as well as in eggs produced by their F1 offspring (Egg_F1). Functional predictions of the microbial communities revealed a significant decrease in the relative abundance of substance dependence pathway in LCS_F. Moreover, this pathway exhibited relatively lower abundance levels in both Egg_L and Egg_F1 compared to Egg_E. These findings validate that long-term cold storage can greatly modify the bacterial composition within H. axyridis, thereby expanding our understanding of the intricate bacteria-insect host interactions.

The morphological diversity of insect mouthparts is closely related to changes in food sources and diets. Research into the structures of insect mouthparts may help to establish a fundamental basis for a better understanding of insect feeding mechanisms. In this study, we examined the fine morphology of the mouthparts of Illeis chinensis using scanning electron microscopy. We paid particular attention to the types, quantities, and distribution of sensilla on the mouthparts. Our results showed that the basic components of the mouthparts of I. chinensis are the same as those in other lady beetles, i.e., the labrum, mandible, maxillae, labium, and hypopharynx. We also found structural specialization indicating adaptation to fungal feeding. On the mouthparts, there are eight kinds of sensilla and two kinds of glandular structures, including sensilla chaetica, sensilla basiconica, sensilla styloconica, sensilla coeloconica, sensilla campaniformia, sensilla placodea, sensilla digitiformia, Böhm bristles, perforated plates, and cuticular pores. This is the first time that sensilla digitiformia has been reported in ladybirds. Finally, variations in mouthparts among ladybirds with differing diets, as well as the putative functions of each of the mouthparts and sensilla, were discussed. This research can provide a reference for understanding the functions of the mouthparts in ladybird feeding behavior and thereby contribute to the development of precise insect behavior regulation and management strategies.

BACKGROUND: Pollen is a common plant-derived food source for predatory ladybird beetles under field conditions, yet the potential for pollen to improve the quality of artificial diets remains largely unexplored. In this study, we developed three pollen diets by incorporating varying proportions of canola bee pollen (7.5%, 15.0% and 22.5% with 2.5%, 5.0%, and 7.5% of water, respectively) into a conventional diet. The feeding efficiency of Harmonia axyridis, an omnivorous predator, was evaluated and compared on three pollen diets, a conventional nonpollen diet and pea aphids. RESULTS: The larvae fed a medium or high pollen diet exhibited significantly higher survival in the 4(th) instar, pupa and adult stages than those fed a nonpollen diet. These larvae also developed into significantly heavier adults, and their survival rates in adulthood were comparable to those fed pea aphids. Specifically, we revealed the underlying mechanisms through which a high pollen diet enhances pupal development. Consumption of high pollen diet versus nonpollen diet resulted not only in a significant decrease in pupal glycogen content, but also an increase in adult lipid content. Both diet treatments induced similar changes in carbohydrate and glycogen content compared to the aphid diet while exhibiting different alterations in pupal protein content and adult lipid content. Furthermore, the transcriptome analysis revealed that the nutrient metabolism, immune response, and cuticle development pathways were predominantly enriched among the differentially expressed genes (DEGs). CONCLUSION: Canola bee pollen offers diverse advantages in terms of rearing H. axyridis larvae with an artificial diet, which will advance the development of effective diets for predaceous coccinellids. (c) 2024 Society of Chemical Industry.

Mouthparts are the feeding organs of insects, which play vital roles in the feeding process. The morphology of insect mouthparts has greatly evolved according to different foods and feeding habits. Therefore, studying the structure of the mouthparts is the key to understanding their feeding mechanisms. Vibidia duodecimguttata is an important biological control agent for powdery fungus. In this study, the fine morphology of the mouthpart of V. duodecimguttata was studied by scanning electron microscopy. The basic components of mouthpart of V. duodecimguttata are similar to those of other ladybeetles, while the specific morphology of each part is different. In total, six kinds of sensilla were identified on mouthpart, and twelve types of sensilla were divided according to their morphology, length and distribution. In addition, two kinds of glandular structures were also found, namely perforated plates and cuticular pores. Finally, the morphological differences between mycetophagous and other feeding habits ladybeetles were compared, and the function of each kind of sensilla was discussed, which may establish a solid foundation for further understanding of the feeding mechanism of ladybirds.

The multicolored Asian ladybird beetle Harmonia axyridis is an important predatory natural enemy in alfalfa fields in China.The pea aphid Acyrthosiphon pisum and the thrip Odontothrips loti are two serious piercing-sucking pests in alfalfa fields.In this study,predatory functional response and predation preference were measured to clarify the biological control potential of H.axyridis towards A.pisum and O.loti.Briefly,the2 nd —3 rd instar nymphs of A.pisum and adults of O.loti were provided as prey for 1 st —4 th instar larvae and the female adults of H.axyridis,respectively.The results showed that the predatory functional response of the larvae and female adults of H.axyridis feeding on both of two prey species fitted with the HollingⅡmodel.Feeding on A.pisum nymphs,the 4 th instar larvae of H.axyridis displayed the highest predation ability,followed by the female adults.Meanwhile,the predation ability of the 1 st ,2 nd ,and 3 rd instar larvae gradually decreased with the reduction of developmental stage.When feeding on O.loti adults,the female adults of H.axyridis exhibited the highest predation ability,followed by the 4 th instar larvae,while the 2 nd and 3 rd instar larvae showed relatively low predation ability.Feeding on A.pisum nymphs and O.loti adults,the searching efficiency of the 1 st —4 th instar larvae and female adults of H.axyridis decreased with increasing prey density.When H.axyridis 4 th instar larvae and female adults were fed A.pisum nymphs and O.loti adults at different ratios （40:80,60:60 and 80:40）,the 4 th instar larvae preferred A.pisum with a predation preference index （D）＞1,whereas the female adults showed no preference with a predation preference index （D）＜1.In conclusion,H.axyridis has great control ability against the2 nd —3 rd instar A.pisum nymphs and O.loti adults,and the 4 th instar larvae and female adults exhibit especially higher predation capability compared to the younger larvae.The 4 th instar larvae of H.axyridis prefer A.pisum nymphs when they coexisted with O.loti adults.

Long-term cold storage is a commonly used technique in mass rearing of natural enemies, but it brings a diversity of negative effects, especially for the laboratory-reared biocontrol agents. Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an important natural enemy of aphids. In this study, the laboratory-reared H. axyridis adults were stored at 6 °C for up to 120 days, and the accompanying effects on maternal and progeny fitness were evaluated and compared with the non-stored beetles (control). Before storage, the newly emerged adults were fed with β-carotene-amended artificial diet for ten days and then acclimated at 15 °C for two days. The mass and trehalose content of the beetle were inversely proportional to the storage duration. The survival rates of the cold-stored beetles decreased as the storage duration increased. However, the survival rates were still above 50% after 120 days in storage (DIS-120). The DIS-120 beetles had a similar fecundity but a significantly longer pre-oviposition period than the control beetles. The egg hatch rates of the DIS-120 beetles were above 60% during the first six days and then dramatically decreased to near zero after day 13. However, the egg viability of the fertility-reduced beetles could be partially restored to approximately 40% by re-mating with non-stored partners. The F1 offspring of the DIS-120 beetles also had a sustained high fecundity but significantly lower egg hatch rate than the F1 offspring of the control beetles. This study demonstrated that the laboratory-reared H. axyridis could be cold stored for approximately 120 days, and their reproductive capability was still acceptable.

异色瓢虫Harmonia axyridis是我国常见的一种捕食性天敌昆虫,其基于黑色素的体色在环境适应中发挥着重要作用.多巴胺(dopamine,DA)是昆虫合成黑色素的一类重要前体物质,同时在调节生理活动方面具有重要作用,但尚不清楚多巴胺在异色瓢虫生长发育中的作用.本实验室前期发现一异色瓢虫浅色突变体gr,其体色的黑化程度明显浅于野生型.本研究以该突变体为研究对象,以添加不同浓度DA的人工饲料(10 mg/g(D-H)、1 mg/g(D-M)、与0.1 mg/g(D-L))饲养幼虫,测定生长发育相关参数及新羽化成虫的鞘翅颜色参数.结果显示:桃蚜Myzus persicae饲喂至2龄的gr取食对照饲料后无法成功发育至3龄,而取食添加DA的饲料后可发育至4龄,但不同饲料间的存活率无显著差异,同时D-L处理的3龄幼虫发育时间显著短于D-H与D-M.桃蚜饲喂至4龄后取食人工饲料,D-M处理的化蛹率、羽化率、雌雄虫体重及鞘翅黑色斑点的Brightness值均高于其它两种饲料及对照处理,并且D-L处理新羽化成虫鞘翅黑色斑点的Brightness值最小(颜色最黑).上述结果表明DA在异色瓢虫幼虫生长发育中具有重要作用,但受浓度影响;幼虫期补充DA可影响成虫鞘翅颜色.

The lady beetle Hippodamia variegata is an important biocontrol agent of many aphids. In this study, the fine morphology of antennae as well as the typology, morphology and distribution of antennal sensilla were comprehensively examined by scanning electron microscopy. The antennal morphology of female and male are similar and consist of the scape, pedicel, and nine flagellomeres. No significant difference was detected in the length of each segment between two sexes, while the male antennae are much stronger than females. In total, six types of sensilla can be defined on antenna, including Böhm bristle, sensilla chaetica (with three subtypes), sensilla basiconica (with three subtypes), sensilla trichodea, sensilla placodea and sensilla coeloconica. It is worth noting that sensilla chaetica III distributed only on the fixed position of male antennae. In addition, the functional morphology of antennae of H. variegata were compared with other lady beetles from multiple perspectives. Specially, the function of sensilla were also discussed according to their morphology, location and information from previous studies.

[目的]七星瓢虫Coccinella septempunctata与多异瓢虫Hippodamia variegate是重要的捕食性天敌,在生物防治中具有广泛的应用前景.开发高效饲养装置以减少幼虫自相残杀率是实现2种瓢虫规模化饲养的重要技术.[方法]在培养皿中增加不同设计的隔断,形成3种饲养盒(Con-A、Con-B和Con-C),以空培养皿作为对照.饲养16头1龄幼虫,通过一系列参数筛选最佳隔断设计.[结果]2种瓢虫幼虫自相残杀主要发生在饲养5d后,但Con-C中的七星瓢虫存活数下降缓慢;在3种饲养盒中,多异瓢虫存活数的下降趋势均弱于对照.从Con-C中获得的七星瓢虫成虫数最多,显著高于对照及其他饲养盒;从3种类型饲养盒中获得的多异瓢虫成虫数均高于对照,但差异不显著.2种瓢虫幼虫主要选择在饲养盒的隔断上化蛹.从Con-A中获得的成虫个体相对较大,但雌雄具有不同变化.[结论]在培养皿中增加隔断有利于高密度饲养七星瓢虫与多异瓢虫幼虫,为进一步开发高效、操作简便的幼虫饲养盒奠定了理论基础.

在人工饲料中分别添加质量分数为2％、4％、6％的凝固剂(卡拉胶、食用明胶、海藻酸钠),探究异色瓢虫幼虫各龄期的存活率及发育历期.结果 表明,添加食用明胶效果相对较好,部分幼虫可发育至成虫,但对存活率具不利影响,且各龄期的发育时间较不添加凝固剂显著延长;添加海藻酸钠的效果最差,所有幼虫不能正常化蛹,当人工饲料中海藻酸钠的浓度为6％时几乎无幼虫能正常发育至2龄.综合来看,添加3种凝固剂的效果均不理想.

七星瓢虫是一种重要的捕食性天敌,在生物防治中应用广泛.为了探究贮藏前补充人工饲料对该瓢虫低温耐受力的影响,本研究通过在贮藏前对新羽化成虫饲喂人工饲料(简称AD)及豌豆蚜(对照,简称AP),以6℃下不同时间后的适合度来评价两个处理的低温耐受力.结果 表明:随着贮藏时间延长,AD成虫的存活率呈下降趋势,在60 d时降至80％,但AP在整个贮藏期均具有较高存活率(＞95％)且AP-45显著高于AD-45;AD成虫体质量损失随贮藏时间延长也显著增加,但均低于AP;AD-60仍具较高生殖力(产卵量为46.4粒,孵化率为80.6％),与AP-60差异不显著.结果 表明人工饲料可作为七星瓢虫成虫贮藏前的一种替代食物,将在进一步开发经济、高效的低温贮藏技术中发挥重要作用.

The lady beetle Coccinella transversoguttata is an important biocontrol agent of aphids. As the main the feeding apparatus, mouthparts play essential roles in feeding process, and the morphological variation of mouthparts is correlated with variation in food source and feeding behavior. To better understand the feeding behavior of C. transversoguttata, we studied the functional morphology of mouthparts, with special attention to the fine morphology of each part of mouthpart and various kinds of sensilla. The mouthpart of C. transversoguttata is typical mandibulate type that composed of labrum, mandible, maxillae, labium, and hypopharynx. Detailed descriptions were given about the fine morphology of each part, and various types of sensilla were identified and classified. In total, two types of sensilla chaetica, four types of sensilla basiconica, two types of sensilla styloconica, two types of sensilla placodea, and one type of cuticular pore were identified according to their length, morphology and distribution. Specially, the putative function of each part of mouthpart as well as each kind of sensilla and their coordinative mechanisms in feeding process were discussed. These results would lay a solid foundation for understanding the feeding mechanism of lady beetles.

The effects of various factors on intraguild predation (IGP) between predators have been widely investigated. However, little is known about the influence of these factors on IGP between predators and parasitoids. Under laboratory conditions, we studied the effects of starvation period of predator, plant dimension, and extraguild prey density on IGP between Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and Aphidius gifuensis Ashmead (Hymenoptera: Braconidae), two natural enemies of Myzus persicae (Sulzer) (Hemiptera: Aphididae). Both H. axyridis fourth instar and adults consumed A. gifuensis mummies. H. axyridis fourth instar and adults starved for 24 and 48h had a higher frequency of IGP than those that were not starved. However, the number of aphids and mummies consumed by H. axyridis did not differ between the 24 and 48h starvation treatments. Although IGP still occurred, mummy consumption decreased with increasing aphid density and plant dimension. In addition, H. axyridis consistently preferred aphids to mummies. Our results indicate that prey preference of H. axyridis, a shorter starvation period of predator (<48h), larger plant dimension, and higher extraguild prey density could reduce the frequency of IGP by H. axyridis on A. gifuensis, and thus decrease the negative impact of IGP on aphid control.

Hippodamia variegata is an important predator of aphid pests. In this study, we determined the complete mitochondrial genome (mitogenome) of H. variegata. The mitogenome is 17,823 bp in length, consisting of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and one non-coding control region. Initiation codons ATA, ATG, ATT, and AAT were identified in two, five, five, and one PCGs, respectively, whereas stop codons TAA or TAG were found in eight genes except for five genes which use incomplete stop codon T–. The phylogenetic analysis indicated that three species in Hippodamia (H. variegata, H. convergens, and H. undecimnotata) were closely related and had a close relationship with the genus Harmonia.

Micropyles in insects are small openings that allow sperm entry into, and the number was usually decreased on unfertilized and (or) undeveloped eggs. However, reports showed that Harmonia axyridis, a reproductive success model, deposited similar number of micropyles on undeveloped and developing eggs. Thus, it was confusing whether micropyles in H. axyridis were unaffected. To solve this confusion, two experiments were conducted here. Firstly, virgin female and four different days delayed mating (DDM) experiments were conducted to reveal the effects of fertilization stimulus and delayed-fertilization. Secondly, intercrosses between a light-colored mutant (HAM, an adaptive deficiency) and wild type (HAW) were conducted to further reveal whether there were female and male interactions. We found that (1) eggs produced by virgin and DDM females had significantly less micropyles than control. Even so, more than 18 micropyles were observed on eggs following fertilization and, consequently, egg production as well as hatch rate was not negatively affected by mating delay; (2) number of micropyles was significantly varied among the four reciprocal crosses and virgin HAW female. Specifically, the heterozygous eggs (Cross-D) and wild-type homozygous eggs (Cross-B) respectively had the least and maximum micropyles, and eggs from virgin HAW female had significantly less micropyles compared to those from HAW female (Cross-B or Cross-C), but the number was significantly higher than those from HAM female (Cross-A or Cross-D). These results informed us that the number of micropyles in H. axyridis is plastic but maintaining a high-quantity that offers many benefits, which should contribute to its reproduction success.

[目的]全面了解甘肃农业大学校园建筑上越冬瓢虫的多样性.[方法]通过2018年10月中下旬至11月上旬在校园建筑的窗户缝内采集越冬的瓢虫成虫,研究越冬瓢虫及不同色斑型的相对丰盛度及雌雄性比.[结果]异色瓢虫(Harmoniaaxyridis)、菱斑巧瓢虫(Oenopiaconglobate)与二星瓢虫(Adaliabipunctata)3种瓢虫成虫集聚在一起进行越冬(共计848头),其中异色瓢虫的相对丰盛度指数最大(81.13％),为优势种.在上述3种瓢虫的越冬种群中,均是黄底型个体的相对丰盛度指数最大,分别为75.44％,62.10％与90.10％,为优势色斑型;异色瓢虫黄底型中的Har-Y7,Har-Y8与Har-Y93种斑型的个体数量较多.异色瓢虫与菱斑巧瓢虫的雌雄性比分别为1.05与0.94,而二星瓢虫种群的性比为0.81.[结论]甘肃农业大学校园建筑上具有种群数量较大的越冬瓢虫种群,给正常工作造成了一定不利影响,需采取有效措施减少瓢虫的侵入并可通过收集进行合理保护和利用.