Introduction
Lateralisation, a phenomenon concerning the left-right asymmetrical organisation of brain functions and behaviours, has captivated the interest of neuroscientists (Güntürkün et al., Reference Güntürkün, Ströckens and Ocklenburg2020; Labache et al., Reference Labache, Ge, Yeo and Holmes2023). It represents an intriguing concept in neuroscience, enhancing brain efficiency by enabling the concurrent left-right processing of multiple information streams (David Fernandes and Niven, Reference David Fernandes and Niven2020; Desaunay et al., Reference Desaunay, Guillery, Moussaoui, Eustache, Bowler and Guénolé2023). There are two levels of laterality: individual-level laterality, where an individual displays a preference towards one side, and population-level laterality, where most individuals in a population exhibit behaviour that is consistently asymmetric towards the same side (Chapelain et al., Reference Chapelain, Pimbert, Aube, Perrocheau, Debunne, Bellido and Blois-Heulin2015; Versace et al., Reference Versace, Caffini, Werkhoven and de Bivort2020). In insects, behavioural asymmetries become have been reported during several tasks and in particular during mating phases (Takanashi et al., Reference Takanashi, Nakano, Surlykke, Tatsuta, Tabata, Ishikawa and Skals2010). These phases involve the development of premating and mating behaviours, characterised by lateralised movements, i.e. movements to the right or left (Kavallieratos et al., Reference Kavallieratos, Boukouvala, Gidari, Di Giuseppe, Canale and Benelli2023). These directional variations play a significant role in mating success, offering distinct differences in biological fitness (Vallortigara and Rogers, Reference Vallortigara and Rogers2005; Dadda et al., Reference Dadda, Zandona, Agrillo and Bisazza2009; Vallortigara and Rogers, Reference Vallortigara and Rogers2020). While research on lateralised traits has primarily focused on vertebrate animals (Stieger et al., Reference Stieger, Wesseler, Kaiser, Sachser and Richter2023; van Dijk et al., Reference van Dijk, Bhattacharjee, Belli and Massen2023; Wang et al., Reference Wang, Luo, Lin, Xu, Gu, Bu, Bai and Li2023), an increasing number of studies are shedding light on individual and population-level brain and behavioural asymmetries in various invertebrate species (Benelli et al., Reference Benelli, Romano, Stefanini, Kavallieratos, Athanassiou and Canale2017; Romano et al., Reference Romano, Benelli and Stefanini2017). The lateralisation of courtship and mating behaviour has been examined in several insect species, including hymenopteran parasitoids (Romano et al., Reference Romano, Benelli, Stefanini, Desneux, Ramirez-Romero, Canale and Lucchi2018) (Romano et al., Reference Romano, Benelli, Kavallieratos, Athanassiou, Canale and Stefanini2020), stored-product beetles (Kavallieratos et al., Reference Kavallieratos, Boukouvala, Gidari, Di Giuseppe, Canale and Benelli2023; Othman et al., Reference Othman, Elias and Zainalabidin2023), mosquitoes (Benelli, Reference Benelli2018), and a calliphorid fly (Benelli et al., Reference Benelli, Romano, Messing and Canale2015a). In this paper, we add to this growing body of data by investigating the lateralisation of courtship and mating behaviour in Ostrinia furnacalis Guenée (Lepidoptera: Crambidae). Exploring the behavioural ecology of an insect pest species holds promise for pioneering approaches within Integrated Pest Management (IPM), offering innovative strategies for pest control and conservation (Avosani et al., Reference Avosani, Nieri, Mazzoni, Anfora, Hamouche, Zippari, Vitale, Verrastro, Tarasco and D'Isita2023).
The Asian corn borer, O. furnacalis, is a polyphagous nocturnal moth, and a pest causing significant damage to major crops in Asia and Europe (Li et al., Reference Li, Feng, Ji, Huang and Tian2021; Kim et al., Reference Kim, Jung, Kim and Kim2022). It is known for its intricate mating rituals, where mate selection predominantly hinges on male age and vitality (Frolov et al., Reference Frolov, Shchenikova, Selitskaya, Grushevaya, Zhukovskaya, Fedoseev, Kuzmin, Lastushkina, Kurenshchikov and Kurenshchikov2022). Investigating the courtship of O. furnacalis, including the role of lateralisation, can yield valuable insights into effective strategies for population control and crop damage mitigation (Boukouvala et al., Reference Boukouvala, Kavallieratos, Canale and Benelli2022). Specifically, studying the sensory cues and behavioural elements involved in O. furnacalis mating behaviour can help identify potential targets for pest management, such as using pheromones or other attractants (Yao et al., Reference Yao, Zhou, Li, Liu, Zhao, Wei, Du and An2021). Variations in ultrasonic sounds and pheromones are closely related to each other in moth species and can profoundly impact mate recognition, reproductive isolation, and speciation (Takanashi et al., Reference Takanashi, Nakano, Surlykke, Tatsuta, Tabata, Ishikawa and Skals2010; Arminudin et al., Reference Arminudin, Wijonarko and Trisyono2020). Our study involved the exploration, observation, and quantification of lateralisation in the courtship and mating behaviour of O. furnacalis. Our goal was to uncover patterns of population-level lateralisation during courtship and mating behaviour and to elucidate how these variances might impact the mating success of male insects. The investigations of these selected lateralised behaviours during male–female interactions aim to enhance our understanding of O. furnacalis behavioural ecology and the significance of lateralised traits within this species.
Materials and methods
Experimental site
The study was conducted in the Agricultural Entomology and Pest Control laboratory and Conservation Tillage Pest and Disease Monitoring Base at Jilin Agricultural University (43.815°N, 125.398°E).
Insect culture
Insects were collected from maize fields (43.815°N, 125.391°E) during early August 2023 with pheromone traps (for male adults) and aerial nets (for female adults), and transported within a plastic container (height: width: length; 23 cm × 45 cm × 70 cm) to the laboratory for mating, approximately 3 km away from the maize fields. The insects were housed in mesh cloth cages (height: width: length; 16 cm × 16 cm × 16 cm; 13 adult parent pairs per cage), at a relative humidity (RH) of 65 ± 5% and a temperature of 26 ± 2 °C. A butter paper was placed on the upper side of the mesh cloth cage for egg laying. A diet comprising 10% sugar-soaked cotton balls (10 ml water) was provided to parent adults. After an incubation period of 2–4 days, eggs were collected and placed in a plastic container (height: width: length; 23 cm × 45 cm × 70 cm), where larvae were fed with a self-made artificial diet (water, wheat germ flour, yeast powder, agar, sucrose, vitamin C (VC), sorbic acid, and nipagin; Liu et al., Reference Liu, Feng, Abbas, Abbas, Hafeez, Han, Romano and Chen2023) until reaching the pupal stage.
Experimental setup for observation of courtship and mating behaviour
To prevent any premature mating interactions among the emerging adults, O. furnacalis pupae were individually isolated in plastic round cups with lids (3.5 cm diameter × 3.5 cm height), which had small holes and contained cotton inside to ensure proper air circulation and humidity access. Newly emerged adult male–female pairs were introduced into the experimental containers (height: width: length; 73 cm × 53 cm × 45 cm) to study courtship and mating behaviours. We observed lateralised courtship and mating behaviours in a total of 150 male–female pairs. To improve the precision of our observations, the experiment was replicated three times, each time with an approximate cohort of 50 adult male–female pairs. It is important to note that only adult pairs displaying mating interactions were included in the analysis; any pairs not displaying such behaviour were omitted from the final dataset. The final sample size for analysis comprised 119 male–female mating pairs (adult pairs exhibited mating interaction out of 150 male–female pairs), aggregated from all three independent repetitions.
A 12-hour observation was conducted for each of the three repetitions using a REOLINK® night vision camera (model number: Reolink Duo 2 Wifi; OS Supported: Windows, Mac, iOS, Android). The same container was used consistently for all three repetitions. The process involved conducting one repetition for 12 hours, removing adults, proceeding with the next repetition for another 12 hours, and repeating the cycle for the third repetition. The camera was equipped with 1/2.7” CMOS sensors and recorded video at a resolution of 4608 × 1728 (8.0 Megapixels) with a frame rate of 20 frames/second to record the insects’ behaviours. The experimental setup consisted of a large plastic container with two compartments, each maintained under controlled conditions of 65 ± 5% RH and a temperature of 26 ± 2 °C. The upper compartment (height: width: length; 63 cm × 53 cm × 45 cm) served as the habitat for the insects, while the inner compartment (height: width: length; 10 cm × 10 cm × 8 cm) housed the night vision camera. To ensure clear and unobstructed video recordings, the camera lens was positioned within the mating chamber. It was connected to an Android mobile phone with a dedicated Android application for seamless recording and data storage management. The night vision camera featured a memory card slot for directly storing recorded videos and captured pictures.
Throughout the observation period, the camera was placed approximately 1 m from the focal insects to optimise video quality and capture detailed behavioural patterns. Leveraging night vision technology, the insects’ activities were monitored during the dark period when their natural mating behaviours were most frequent. Following data collection, recorded videos were stored on a memory card for subsequent analysis. These videos were examined for courtship displays, mating sequences, and the manifestation of any lateral biases (fig. 1).
After behavioural displays, observations were made regarding the male's selection of the side for approach to the female's posterior of the abdomen. Furthermore, the specific side chosen by the male for intromissive copulation at 180° turn was recorded; this manoeuvre is pivotal for facilitating the establishment of end-to-end genital linkage and initiating copulation. This evaluation sought to elucidate the potential influence of lateralised behaviours on the mating process in O. furnacalis (Table 1).
Statistical analysis
The impact of lateralisation on differences in the mean duration and/or number of courtship and mating behaviours acts was analysed using Origin Pro 2023b (Northampton, Massachusetts, USA) with non-parametric statistics (P < 0.05) because of non-normal (Shapiro–Wilk test, P < 0.05) data distribution and non-homoscedasticity (Levene's test, P < 0.05). Laterality differences between the numbers of males approaching the left or right side of the female, as well as the number of males turning 180° to the left or to the right in an attempt to copula during courtship interactions, were analysed using an Chi2 (χ2) test with Yates’ correction (P < 0.05) (Loriaux, Reference Loriaux1971).
Results
Among the adults under observation, only 119 male–female pairs displayed mating behaviours and were consequently included in the analysis. When a male encounters a female, a sequence of distinct behaviours unfolds. Initially, the male engages in a sequence of actions, including ultrasonic courtship songs through wing vibrations, exhibiting male aggression towards the female, and softly tapping the female's body with his antennae. As the male approaches the tip of the female's abdomen, he carefully touches the posterior of her abdomen with his antennae. This interaction frequently elicits a response from the female, where she raises her abdomen, indicating her receptivity. Following this, the male may respond aggressively if met with rejection or if the female attempts to evade the courtship. During this phase, the male rotates his body, forming a 180 ° angle relative to the female (figs 2 and 3A-B). In the later stages of courtship, the female typically becomes motionless in response to the male's persistent courtship behaviours (Table 2). This motionlessness serves as a crucial signal, indicating her readiness to engage in end-to-end genital contact – a pivotal step in initiating copulation.
Values are means followed by standard errors (SE) within each row, similar letters indicate no significant differences between side-biased parameters (Wilcoxon test, P < 0.05).
The success of mating was notably higher when O. furnacalis males approached females from the left side during sexual interactions (χ2 = 6.700; df = 1; P < 0.0001), while approaches from the right side did not significantly impact mating success (χ2 = 0.0001; df = 1; P = 0.988) (Table 2). Additionally, turning direction to the left while attempting copula resulted in a higher male mating success (χ2 = 8.130; df = 1; P < 0.0001) compared to males displaying a right-biased turning behaviour (χ2 = 1.944; df = 1; P = 0.717). (See Table 3.)
Values are means followed by standard errors (SE); within each row, different letters indicate significant differences among side-biased parameters (Kruskal–Wallis test, P < 0.05).
Mating success in males was significantly influenced by ultrasonic courtship songs (χ2 = 15.130; df = 1; P < 0.0001), male aggression towards female displayed during courtship (χ2 = 5.590; df = 1; P = 0.011), female courtship rejection or escape (χ2 = 4.640; df = 1; P = 0.051), as well as the number of the male copulation attempts (χ2 = 6.504; df = 1; P = 0.021). The male's mating success, however, remained unaffected by the duration of the antennal tapping by the male on the female (χ2 = 2.001; df = 1; P = 0.067) and duration of the antennal tapping by the male on the female (χ2 = 1.651; df = 1; P = 0.922). (See Table 2.)
No significant differences between males approaching females with left- or right-biased directions were observed in the duration of the male's ultrasonic courtship songs (χ2 = 1.900; df = 1; P = 0.071), male aggression towards female for courtship (χ2 = 1.504; df = 1; P = 0.091), the duration of the male antennal contact with the posterior of female (χ2 = 0.071; df = 1; P = 0.990), (χ2 = 0.043; df = 1; P = 0.720), and female courtship rejection or escape (χ2 = 0.904; df = 1; P = 0.661), female motionlessness in response to male courtship behaviours (χ2 = 0.029; df = 1; P = 0.000), the number of the male copulation attempts (χ2 = 0.027; df = 1; P = 0.891), as well as the duration of intromissive copulation (χ2 = 0.026; df = 1; P = 0.876). (See Table 2.)
Turning direction was not associated with the duration of the male's ultrasonic courtship songs (χ2 = 0.016; df = 1; P = 0.897), male aggression towards female during courtship (χ2 = 3.969; df = 2; P = 0.137), the duration of the male antennal contact with the posterior of female (χ2 = 1.147; df = 2; P = 0.563), male aggression towards female in response to courtship rejection or escape (χ2 = 3.969; df = 2; P = 0.137), and female motionlessness in response to male courtship behaviours (χ2 = 5.128; df = 2; P = 0.077), the number of the male copulation attempts (χ2 = 3.527; df = 1; P = 0.060), or the duration of intromissive copulation (χ2 = 0.484; df = 1; P = 0.486). (See Table 3.) However, the number of male copulation attempts was significantly affected by the side chosen by the male to turn 180° and attempt copulation (χ2 = 16.017; df = 2; P < 0.0001). Males that turned 180° from the female left side performed significantly more attempts to insert their aedeagus into the female's genital chamber, if compared to right-biased turning males, which started copulation earlier with lower copulation attempts (Table 3).
Discussion
In the context of lateralised courtship and mating behaviours in male adults of O. furnacalis, various critical behaviours come into play to ensure successful mating, as reported in recent research (Sun et al., Reference Sun, Bu, Su, Guo, Gao and Wu2023). Our research has discovered novel lateralisation in mating behaviours of O. furnacalis adult males and females, particularly in response to female calling behaviours for mating. Upon encountering a female, the male engages in a series of distinct actions. In the results section, the whole sequence of ethological units is described. Our general observations align with previous studies on other Ostrinia species, emphasising the consistency of these courtship and mating behaviours, specifically the role of male ultrasonic courtship songs across this group of insects (Nakano et al., Reference Nakano, Takanashi, Skals, Surlykke and Ishikawa2010; Nakano et al., Reference Nakano, Takanashi, Surlykke, Skals and Ishikawa2013; Nakano and Nagamine, Reference Nakano and Nagamine2019; Rizvi et al., Reference Rizvi, George, Reddy, Zeng and Guerrero2021; Zweerus et al., Reference Zweerus, van Wijk, Schal and Groot2021). Specifically, our results on the importance of laterality find resonance with numerous studies on lateralisation in mating behaviours in other insects species, including the rock ant (Temnothorax albipennis) (Hunt et al., Reference Hunt, Dornan, Sendova-Franks and Franks2018), Khapra beetle (Trogoderma granarium) (Kavallieratos et al., Reference Kavallieratos, Boukouvala, Gidari, Di Giuseppe, Canale and Benelli2023), mosquitoes (Culex pipiens) (Benelli, Reference Benelli2018), olive fruit fly (Bactrocera oleae) (Benelli et al., Reference Benelli, Romano, Messing and Canale2015a; Zaynagutdinova et al., Reference Zaynagutdinova, Kölzsch, Müskens, Vorotkov, Sinelshikova, Giljov and Karenina2022) and Mediterranean fruit fly (Ceratitis capitata) (Benelli et al., Reference Benelli, Donati, Romano, Stefanini, Messing and Canale2015b). This broader alignment with the literature reinforces the generalisability of our findings to a broader context of insect behaviour and adds to the growing body of knowledge in this field.
In the present study, we have identified two specific behavioural displays in O. furnacalis that exhibit within-population dimorphism in laterality. It was consistently observed that a significant majority of male O. furnacalis, during courtship and mating, preferred to position themselves at the tip of the female's abdomen. In doing so, they occasionally engaged in antennal tapping and palpation on the left side of the female's body. Additionally, males strongly preferred clockwise and anti-clockwise rotations (right and left turns) when forming a 180-degree angle with the female's body, which is crucial for the end-to-end genital linkage. Notably, we observed that males approaching females from the right-side were primarily left-biased in their 180° turning, while those approaching from the left-side exhibited a right-biased in their turning behaviour. It is important to underline that these lateralised traits did not substantially impact the main behavioural parameters characterising courtship and mating in O. furnacalis. However, it is noteworthy that males executing a 180° turn from their left-side appeared to make fewer copulation attempts, suggesting a potentially better orientation and efficiency in achieving genital linkage among right-biased males. Many studies agree with our finding in turning 180° while mating with various insects (Benelli et al., Reference Benelli, Romano, Messing and Canale2015a; Chivers et al., Reference Chivers, McCormick, Warren, Allan, Ramasamy, Arvizu, Glue and Ferrari2017; Kiss et al., Reference Kiss, Toth, Jocsak, Bartha, Frenyo, Barany, Horvath and Zsarnovszky2020; Romano et al., Reference Romano, Benelli and Stefanini2022)
Significantly, our study unveiled a correlation between mating success and lateralisation. Males that approached females from the right-side and those that preferred leftward turning exhibited significantly higher mating success rates. This finding marks the first evidence of population-level lateralised mating traits in O. furnacalis, a species previously known primarily for motor bias in lateralisation. Our results align with a substantial body of literature highlighting the prevalence of population-level lateralised traits in social and solitary insect species (Anfora et al., Reference Anfora, Frasnelli, Maccagnani, Rogers and Vallortigara2010; Sakurai and Ikeda, Reference Sakurai and Ikeda2022). Recent studies have reported lateralised traits related to courtship, mating, and genital morphology (Schilthuizen, Reference Schilthuizen2013) in various insects, including lesser mealworm beetle (Alphitobius diaperinus) (Calla-Quispe et al., Reference Calla-Quispe, Irigoin, Mansurova, Martel and Ibáñez2023), earwigs (Nala nepalensis) (Kamimura et al., Reference Kamimura, Matsumura, Yang and Gorb2021), rusty grain beetle (Cryptolestes ferrugineus) (Boukouvala et al., Reference Boukouvala, Kavallieratos, Canale and Benelli2022), encyrtid parasitoids (Anagyrus sp.) (Romano et al., Reference Romano, Benelli, Stefanini, Desneux, Ramirez-Romero, Canale and Lucchi2018), green bottle fly (Lucilia sericata) (Romano et al., Reference Romano, Benelli and Stefanini2021), and Drosophila melanogaster (Versace et al., Reference Versace, Caffini, Werkhoven and de Bivort2020; Lapraz et al., Reference Lapraz, Boutres, Fixary-Schuster, De Queiroz, Plaçais, Cerezo, Besse, Préat and Noselli2023). Our research unveils the existence of lateralised courtship and mating behaviours in O. furnacalis, enriching our comprehension of this species beyond mere motor biases previously reported. This discovery resonates with a broader trend of population-level lateralisation seen across various insect species, underscoring the pivotal role of lateralisation in insect reproductive behaviours.
Theoretical models propose that population-level lateralisation is more likely to develop in social species. The reasoning behind this hypothesis lies in the potential benefits of lateralisation in social interactions (Rogers et al., Reference Rogers, Rigosi, Frasnelli and Vallortigara2013; Frasnelli and Vallortigara, Reference Frasnelli and Vallortigara2018; Ocklenburg et al., Reference Ocklenburg, El Basbasse, Ströckens and Müller-Alcazar2023; Tonello and Vallortigara, Reference Tonello and Vallortigara2023). In social insects, individuals often need to coordinate their behaviours, such as during group movements, foraging, or communication (Johnson, Reference Johnson2010; Feinerman and Korman, Reference Feinerman and Korman2017). Lateralisation, or the consistent preference for using one side of the body or brain, can facilitate efficient and synchronised interactions within the population. This may lead to improved coordination, reduced ambiguity in communication signals, and enhanced overall social cohesion (Frasnelli and Vallortigara, Reference Frasnelli and Vallortigara2018). While the specific mechanisms and advantages may vary across species, the underlying concept is that in social environments, population-level lateralisation could confer adaptive advantages that promote effective group functioning and communication (Vallortigara, Reference Vallortigara2006). However, in many insect species (such as O. furnacalis), the common and intense interactions among individuals, including numerous conflicts and mating events, as well as encounters with other species like predators and host plants, may help explain the widespread occurrence of population-level lateralisation (Casanova, Reference Casanova2020; Manns, Reference Manns, Vonk and Shackelford2022). The theory does not necessarily suggest that social species require population-level lateralisation, but it posits that lateralisation might emerge as an Evolutionary Stable Strategy (ESS) either at the individual or population level, depending on the specific context (Rogers et al., Reference Rogers, Frasnelli and Versace2016; Colombo, Reference Colombo2023; Jacobs and Oosthuizen, Reference Jacobs and Oosthuizen2023).
The discovery of lateralised courtship and mating behaviours across different insect orders suggests that this trait could serve as a pivotal component in the ESS governing the reproductive behaviour of these species (Vidal-Abarca Gutierrez et al., Reference Vidal-Abarca Gutierrez, Nicolás-Ruiz, Sánchez-Montoya and Suárez Alonso2023), While much of this research has traditionally been conducted in laboratory settings to understand the relevance of brain lateralisation as an adaptation to ecological demands (Manns, Reference Manns2021), our study also focuses explicitly on population-level lateralised courtship and mating in O. furnacalis. This provides valuable insights, demonstrating a noteworthy parallel with several vertebrates and invertebrates that exhibit lateral biases in their natural environments, unconstrained by laboratory conditions (Ventolini et al., Reference Ventolini, Ferrero, Sponza, Della Chiesa, Zucca and Vallortigara2005; Koboroff et al., Reference Koboroff, Kaplan and Rogers2008). This study, revealing asymmetries in the behaviour of O. furnacalis, supports the hypothesis that lateralisation is a widespread phenomenon and emphasises the need for increased attention to this topic among behavioural biologists in the context of pest management and ecological studies.
In conclusion, this study provides evidence of lateralised courtship and mating behaviours at the population level in O. furnacalis, offering a contribution to the understanding of these behaviours. Our research advances our fundamental knowledge of the courtship and mating behaviour of O. furnacalis, shedding light on previously unexplored aspects of its reproductive biology. The new insights gained into the reproductive behaviour of O. furnacalis may also hold practical implication by identifying behavioural traits suitable for assessing the quality of mass-reared individuals in pest control programs. Comprehending population-level lateralisation enables the identification of individuals with improved coordination and communication skills. This understanding holds promise for enhancing the effectiveness of pest management strategies by facilitating targeted releases.
Prior to this study, there were no attempts to evaluate the existence and functional importance of lateralised traits within the Crambidae. To advance our understanding, further research efforts need to extend beyond the laboratory setting and into the field to explore the existence of these lateralisation traits in O. furnacalis under natural conditions. The goal of these investigations is to offer a more thorough understanding of the distinct lateralisation traits displayed by this species. The quantification of mating displays in this laboratory study establishes a foundation for further research, enabling future comparative analyses with other insect species. This sets the stage for broader insights into the evolutionary and ecological implications of lateralisation among insect populations.
Availability of data and materials
Not applicable.
Acknowledgements
This work was supported by the Ministry of Science and Technology of China (2022YFD1500701).
Authors’ contributions
Sohail Abbas: Conceptualisation, Writing-Original Draft, Methodology, Data Analysis and Curation; Aleena Alam: Schematic Diagram and Data Curation, Muneer Abbas: Writing-Review and Editing; Arzlan Abbas: Writing-Review and Editing; Jamin Ali: Writing-Review and Editing; Menno Schilthuizen: Critically Revised Manuscript; Donato Romano: Methodology, Critically Revised Manuscript; Chen Ri Zhao: Supervision, Funding, Resources and Writing-Review and Editing.
Competing interests
None.
Ethical approval
Not applicable.