With global landscape and climate change, insect pests have widespread and frequent outbreaks, seriously damaging agricultural and forest services for human wellbeing, particularly the expansion of invasive pests in nonnative ranges (Scherm et al., 2000; Mina et al., 2022). In many countries, chemical pesticides are still the primary control strategy for pests, but excessive utilization of pesticides has led to problems, such as reducing biodiversity of insects in freshwater and terrestrial systems (Beketov et al., 2013), polluting the environment, increasing pest resistance to pesticides, and contributing to global insect pollinator declines (Basset and Lamarre, 2019). Insect pest management has become one of the biggest challenges, such as on organic farms (Kim et al., 2019). Natural enemies are alternative and environmentally friendly means to control insect pests and have received wide attention worldwide (Landis et al., 2000).

The ectoparasitoid beetle, Dastartcus helophoroides Fairmaire (Coleptera: Bothrideridae) is distributed widely in Kyushu and Osaka in Japan, Korea and China (Lyu et al., 2014). This beetle is an important parasitoid of several longhorned beetles in its native range, including Anoplophora glabripennis Motschulsky (Haack et al., 2010), Monochamus alternatus Hope (Lyu et al., 2014), and Batocera horsfieldi Hope (Yang et al., 2014). These longhorn beetles are phytophagous: the larvae usually bore in the large branches and trunks of woody plants, ranging from alive to moribund to dead and decomposing (Hanks, 1999). Many longhorn beetle species cause tremendous economic and ecological losses in forests worldwide, including insect vectors of nematodes (Zhou et al., 2023), such as A. glabripennis and the genus Monochamus. The A. glabripennis is a polyphagous xylophage native to Asia and ranked as one of the top 100 worst invasive species worldwide in North America and Europe (Branco et al., 2022). Potential losses of widespread A. glabripennis outbreaks in compensatory value were equal to approximately 12% of the total economic losses caused by forest pests and diseases in China, exceeding more than US$1.5 billion (Golec et al., 2018). Outside its native range, estimations of potential economic losses exceed US$1 trillion if adjusted to 2021 values, and approximately 35% of urban trees have been destroyed in the USA (Branco et al., 2022). Pine wood nematodes is transported between host trees by cerambycid beetles of the genus Monochamus, and approximately 1.7 million hectares were infected in 19 provinces in 2021, destroying 14 million trees in China’s pine forests (Yu et al., 2023).

Insects use visual and chemical cues from intra- and interspecific communication and the environment to mediate their activities and behaviors, such as reproduction, and foraging, and even to organize and maintain social structures in social insects (Nieri et al., 2022). Many different stimuli signals have often been applied to pest management, such as chemicals, lights, colors, sounds and vibrations (Fleming et al., 2005; Kim et al., 2019; Cavaletto et al., 2021; Van der Kooi et al., 2021; Zapponi et al., 2022). In cerambycid beetles, pheromone-baited traps are a common tool for detecting and sampling insects for surveillance, eradication, or management, and pheromones of more than 100 cerambycid species have been identified to date, including sex attractant pheromones, aggregation-sex pheromones, and nonvolatile contact pheromones (Hanks and Millar, 2016). However, semiochemical-based traps baited with a mixture of host kairomones (plant volatile organic compounds) and/or sex pheromones have still not reached operational efficacy for some Cerambycid beetles in field bioassays; for example, the trapping number of approximately 80% (34/43) of longhorn beetle species was fewer than 10 beetles per 10–14 days (Nehme et al., 2010; Ray et al., 2012; Wickham et al., 2012; Hanks and Millar, 2013; Wickham et al., 2014; Silva et al., 2016; Wickham et al., 2016; Zhu et al., 2017; Xu et al., 2020) (Supplementary Figure S1). Therefore, an effective trapping tool needs to be developed for some longhorn beetles with limited semiochemical-based trapping effects in the future.

Light traps are widely used to monitor and manage the population density of insect pests, and play an important role in physical pest control (Kim et al., 2019). Due to natural light is present in the daytime, the target pest is usually a crepuscular or nocturnal insect, and at least some of the activity occurs at night (Kim et al., 2019; Nieri et al., 2022). Both foraging and mating behavior in A. glabripennis adults occur throughout the day, and the peaking of foraging behavior occurs at night (21:30) (Lyu et al., 2015a). In addition, the mating behavior of M. alternatus also took place throughout the day, particularly during the peak time of activity at night (18:00–24:00) (Luo et al., 2012). Longhorn beetles Phymatodes aereus, Anelaphus pumilus, and Massicus raddei are also nocturnal insects (Mitchell et al., 2015). These results suggested that a light-trapping strategy may be used to monitor and manage the population density of Cerambycid beetles. Although light traps can be used to attract and kill insect pest populations, they can also kill the natural enemies of pests (Luo and Chen, 2016). Therefore, the phototactic behavioral responses of natural enemies should be considered when light traps are used to monitor and manage target insect pests.

The phototactic behavior of insects not only depends on the characteristics of the light source, including light wavelength and intensity, but the other conditions also influence phototactic behavior response rates, such as rhythmicity with photoperiod, light exposure time, sex and gene expression (Kim et al., 2019; Kooi et al., 2021). Although the results of previous study showed that near-infrared light (NIR, 700 nm) is most suitable in attracting D. helophoroides adults, the phototactic response of D. helophoroides have broad spectrum of light (from UV to NIR) and the response rates were not significant difference between UV, blue, green and NIR lights (Wang et al., 2021). In addition, near infrared light (NIR,700 nm) were used to trap Cerambycid beetles has been rarely reported. In the field, UV (or violet), blue, and green lights are usually used to attract and kill target insect pests, including Cerambycid beetles (Luo and Chen, 2016). For example, the beetles (Coleoptera) show a preference for UV, violet (350–440) and green (500–560) wavelength spectra (Kim et al., 2019; Van der Kooi et al., 2021). UV-black-light-blue light traps captured more Cerambycid beetles (Arhopaus ferus) than yellow light traps (Pawson et al., 2009). UV (365 nm) and violet light (420 and 435 nm) are the most suitable wavelengths for attracting adult A. glabripennis at night (Jiang et al., 2023a). Therefore, in order to decrease the trapping rate of natural enemy (D. helophoroides) in the light traps, it is of great significance to reveal the response mechanism of D. helophoroides adults for the UV and visible lights.

The behavioral and physiological changes of insects under light exposure are well established (Kim et al., 2019; Kooi et al., 2021) and are tightly related to gene expression and regulation (Futahashi et al., 2015). RNA-Seq is a powerful tool for the analysis of DEGs, the discovery of novel transcripts, and the identification of key genes (Trapnell et al., 2010). It has been widely utilized in various fields ranging from agriculture to medicine, investigating gene expression changes in response to light exposure and other biotic and abiotic stresses (Hong et al., 2020; Chen et al., 2022). In Diaphorina citri adults, 841 upregulated differential expressed genes (DEGs) and 932 downregulated DEGs, and DEGs play key roles in physiological and biochemical responses such as oxidative stress, protein denaturation, inflammation and tumor development after blue light (400 nm) exposure (Wang F. F. et al., 2023). While 40 DEGs were upregulated and 413 DEGs were downregulated in the Bemisia tabaci after ultraviolet-A radiation, and DEGs were mainly involved in physiological and biochemical responses, including anti-oxidation and detoxification, protein turnover, metabolism (Khan et al., 2023). Many studies have shown that downregulated DEGs are significantly greater than upregulated DEGs after different light exposures and the antioxidant activity is decreased (Cui et al., 2021; Khan et al., 2023). However, these data are insufficient to fully understand the molecular mechanisms underlying the response to light exposure, especially in nocturnal Coleoptera beetles.

In the present study, we investigated the influence of light exposure time, sex, and diel rhythm on the phototactic behavioral response of female and male D. helophoroides under light with different wavelengths, and the gene expression profiles of females and males under white light exposure. Due to UV, violet (350–440 nm) and green (500–560 nm) wavelength spectra were often used to trap Cerambycid beetles, therefore, 6 LED light wavelengths, which were UV (365 nm), violet (420 nm and 435 nm), green (515 nm), and red (600 nm and 660 nm), were selected to investigate the effect of exposure time on the phototactic behavioral responses of females and males, thus providing an appropriate test condition for the next experiment. Then, we displayed the phototactic behavioral responses of females and males under different light wavelengths at five time slots to show diel rhythm on the phototactic behavioral response. Finally, at the transcriptome level, we investigated the gene expression profiles of females and males under different light exposure times (15 and 120 min) of white light relative to dark conditions (control treatment) to explore the response mechanism for light exposure. Thus, these results not only can provide valuable information for the monitoring and management of population density and prediction, but also may expand the understanding of the molecular response mechanism in the nocturnal beetle D. helophoroides to light exposure.

To decrease negative effect of chemical pesticides on the environment, the taxis of insects to artificial lights are widely used to detect, monitor and manage insect pests (Kim et al., 2019; Van der Kooi et al., 2021), such as Tenebrionidae, Curculionidae, Pselaphidae, Silvanidae, Cerambycidae and Scolytinae (Park and Lee, 2017; Marchioro et al., 2020). However, traps with artificial lights can also attract many natural enemies when they are used to detect and manage insect pests (Luo and Chen, 2016; Kim et al., 2019). Therefore, the trapping ability of lights for natural enemies of pests should also be considered in the monitoring and detection of insect pests (Bian et al., 2018). The ectoparasitoid beetle D. helophoroides is an important natural enemy of wood-boring insects and is widely used in controlling cerambycid beetles, including A. glabripennis and M. alternatus (Wang L. et al., 2023; Lyu et al., 2023; Zhang et al., 2023). Therefore, it is vital to explore the response mechanisms of ectoparasitoid beetles to light cue cognition at behavioral and molecular level. Our results showed that female and male D. helophoroides have negative or weak phototaxis at a certain light intensity, and it was influenced by light exposure time, diel rhythm, sex, and light wavelength.

Previous studies have shown that D. helophoroides adults are attracted by NIR light with a peak wavelength of 700 nm and an intensity at 7 lux, and the highest phototactic response rate is approximately more than 60% in the near-infrared light region (Wang et al., 2021). In the present study, males showed the highest preference for 400, 455, and 600 nm (Figure 4A), while females exhibited the highest preference at 660 nm (Figure 4C). The trapping rates were approximately 10.67%–15.83%. We speculate that the light intensity may cause a significant difference between the two studies. In previous study showed that phototactic behavioral rate of adults decreased with increasing light intensity (Wang et al., 2021). In this study, a 6.31 × 10¹⁸ (photos/m²/s) light intensity (approximately 180 lx) was used, which may also contribute to the low trapping rates of adults.

The trapping rate of females and males was also affected by light exposure time. For example, the trapping rate of females at 420 and 600 nm and males at 515 nm under the light exposure with 15 min was higher than under 120 min (Figures 2B, D, E), so the samples were selected in the light exposure time with 0, 15 and 120 min after dark adaptation in transcriptomic analysis. Moreover, the trapping rate was not significantly different between 15 and 120 min (Figures 2A, C, F). In transcriptomic and qRT-PCR data, there was not significant difference in the majority of gene expression (Figure 7A; Figure 9). Therefore, the treatment sample time interval should be extended to response monochromatic light radiation in the further study.

Previous studies have shown that Coleoptera beetles display a preference for UV, violet and green wavelength spectra (350–440 and 500–560 nm) (Kim et al., 2019; Van der Kooi et al., 2021). Using the same behavioral response chamber, both females and males A. glabripennis displayed higher phototactic responses under illumination with 420 and 435 nm wavelengths (violet and blue) at night, with an approximately 74%–82% trapping rate (Jiang et al., 2023a). UV light traps were more attractive to Arhopalus ferus and Prionoplus reticularis (longhorn beetles) than their adjacent two yellow lights (Pawson and Watt, 2009). UV-blue light traps captured 2–4 times more bark beetles Hylurgus ligniperda and Hylastes ater beetles than traps baited with other wavelengths in New Zealand (Pawson et al., 2009). These results suggested that UV and blue light traps can be used to detect and control wood boring pests, including longhorn and bark beetles. In this study, females showed a higher preference for 420, 435, 475, 560, and 630 nm at night from 19:00–21:00 (Figure 3B), but the trapping rate decreased with increasing light intensity (Wang et al., 2021). Therefore, light intensity should be enhanced to reduce the trapping of D. helophoroides when UV and blue light traps are used to detect and manage wood boring pests.

Previous studies have shown that the 24-h rhythm of locomotor activity in female and male D. helophoroides was elevated in the dark phase and reduced in the light phase, and the peak of locomotor activity occurred at 20:30–22:30 during the dark period, while that of adults hardly occurred during light period, indicating that they are nocturnal insects (Lyu et al., 2015b; Lyu et al., 2015c). Further researches showed that increasing the light duration during the dark phase significantly decreased the activity percentage of locomotor, disturbing the normal rhythm of locomotor activity. Moreover, the oviposition ability of females was decreased under light (1, 10, and 100 lx) exposure at night relative to no light (0 lx) at night (Jiang et al., 2023b). In this study, female and male adults exhibited negative phototaxis for LED lights (Figures 5B, D), which is an adaptation strategy to avoid the adverse influence of light exposure.

In the organism response to abiotic stress, a comparative transcriptome analysis was performed using RNA-Seq to examine the cellular responses of plants and animals in response to heavy metals, heat, drought, pathogenesis and insect stress, and up- and downregulated DEGs were identified and analyzed, and potential regulatory mechanisms were speculated or verified under adverse situations (Sun et al., 2022; Wang Z. et al., 2023; Liu et al., 2023). For example, RNA-Seq was used in crayfish experiments under Cu stress, and 4,662 DEGs, including 3,534 upregulated and 1,128 downregulated DEGs, were identified (Wang Z. et al., 2023). In the present study, a total of 1,052 DEGs were identified in the head of D. helophoroides following light exposure for 15 and 120 min, and different comparison groups had different up- and downregulation (Figures 5C–I). These results indicated that transcriptional alterations occurred in the head of this beetle during light exposure for 15 and 120 min relative to dark adoption. STEM analysis revealed that 3 clusters (DEGs) significantly changed in male and 4 clusters significantly changed in females (Figures 7D–K), suggesting that differential response strategies may be employed by female and male beetle at different light exposure times. This corroborates the results of behavioral experiments (Figure 2) that showed that trapping rate changes were observed under different light exposures.

Our previous study showed that the locomotor activity percentage of beetles under the light phase was significantly lower than that under the dark phase, suggesting that long-term light exposure can derange temporal adaptation and decrease organism fitness (Jiang et al., 2023b). In the present study, KEGG pathway analysis showed that the lysosome pathway was enriched (Figure 6B), and all of the relative genes in this pathway were downregulated under light exposure for 15 and 120 min relative to dark adaptation, suggesting that the function of this pathway decreased under light exposure. The autophagy lysosome pathway is a major mechanism for degrading intracellular macromolecules, which is also known to protect adult cells against irreversible states (Fujimaki et al., 2019; Lawrence and Zoncu, 2019). In addition, a previous study also showed that reducing lysosomal function drove cells progressively deeper into quiescence depth, and even into a senescence-like irreversibly arrested state (Fujimaki et al., 2019). Reducing lysosomal function may suggest that light illumination may have a negative effect on this nocturnal beetle. Thus, in transcriptome level, the results also showed that female and male adults have a lower or negative phototactic behavioral response rates to light illumination (Figure 4).

In addition, the focal adhesion pathway was also significantly enriched statistically in the 15 and 120 min light exposure groups (female and male) relative to dark adaptation (Figure 6B and 8 C, Supplementary Table S12, p _adjust < 0.001). Focal adhesions are key modulators of cellular responses to biotic and abiotic stimuli in cell proliferation, differentiation, and motility (Wehrle-Haller, 2012). In crustaceans, focal adhesions have been reported to be involved in Cd, Pb and Cu tolerance through transcriptomic and proteomic approaches (Lu et al., 2019; Jiao et al., 2021; Wang Z. et al., 2023). In crayfish, focal adhesion pathway plays a critical role in the crayfish response to Cu stress and that upregulation of hub genes may increase the survival capacity of crayfish (Wang Z. et al., 2023). However, in our study, genes linked to focal adhesion were significantly downregulated under light exposure for 15 and 120 min relative to dark adaptation (Figure 6B; Supplementary Table S16). In the real environment, there is a significant difference between light stresses and heavy metal stresses. The heavy metal pollutants in aquatic environments are generally widespread. For example, Cu ions are significantly enriched in water, sediment, and cultured fish species around aquaculture farms in the Yangtze River and Taihu Lake, East China (Rajeshkumar et al., 2018; Xiong et al., 2020). Crustacean animals hardly choose the optimal living environment through migration, while nocturnal insects can select a suitable habitat to avoid light exposure through migration. Therefore, crustacean animals may decrease the influence of heavy metals through an upregulated focal adhesion pathway, while the focal adhesion pathway was downregulated in nocturnal insects under light exposure relative to the normal environment (dark adaptation) to impact normal physiological activity.

Furthermore, focal adhesions are specialized sites within the cell, where mechanical force generated within the cell is transmitted to the surrounding ECM, thus influencing its organization and also contributing to cell migration (Burridge, 2017). The compound eye of insects usually regulates the length and shape of the cone, the cross-sectional areas and shapes of the rhabdoms, and the movement of pigment cells to adapt to changes in light and dark environments (Insausti et al., 2013; Chen et al., 2019). For example, cones of M. alternatus were 14.67 ± 0.51 μm in length and formed a conical shape with a narrow and pointed proximal end in the light-adapted state, while cones were much shorter (5.57 ± 0.16 μm) and had a disc-shaped structure with a round and blunt proximal end in the dark-adapted state. The cross-sectional area of the rhabdom decreases by approximately 35% in the light-adapted state relative to that of the dark-adapted state (Wen et al., 2020). Furthermore, photoreceptors have a light/dark adaptation mechanism for adjusting light sensitivity through changes in rhodopsin levels and cellular location in the crepuscular mosquito Anopheles gambiae (Moon et al., 2014). In the present study, GO annotation analysis showed that the DEGs were significantly enriched in cell morphogenesis, cell morphogenesis involved in differentiation, basement membrane, and substrate adhesion-dependent cell spreading under light exposure for 15 and 120 min relative to dark conditions (Figure 6A), suggesting some of cell redistribution during change in the light and dark environment. Moreover, DEGs that were enriched in the focal adhesion pathway were mainly distributed in the cell motility and eventually into regulation of actin cytoskeleton (Figure 10; Supplementary Figure S3). For arthropods, rhodopsin was present within the cytoplasmic compartment during daylight timepoints, while it moved to the rhabdomeres only under dark conditions to enhance visual capability in a low light environment (Sacunas et al., 2002; Hu et al., 2012; Moon et al., 2014). Therefore, these DEGs may regulate changes in cone, rhabdom and pigment cell length and shape to enhance light signal recognition ability. Whether these DEGs can regulate changes in cone cells, movement of pigment cells and cross-sectional areas and shapes of the rhabdoms requires further experiments.

Based on the results from this study and other previous studies (Macias-Muñoz et al., 2019), a potential synergistic molecular network can be proposed for the nocturnal beetle D. helophoroides in response to light exposure (Figure 10). When light photons were received by photoreceptor cells, genes related to the ECM-receptor interaction pathway are downregulated, such as MSTRG. 130, evm.TU.HIC_ASM_0.1906, 1,097, 1,098, evm.TU.HIC_ASM_10.534, and evm.TU.HIC_ASM_8.978 were downregulated under light exposure (15 and 120 min) relative to dark adaptation (Figure 10). Furthermore, these genes also regulated cell morphogenesis and differentiation to decrease the amount of received light quantum, reducing cellular damage. Subsequently, ITGA (evm.TU.HIC_ASM_12.1091) and ITGB (evm.TU.HIC_ASM_11.701) were downregulated; and then on the one hand, RhoGEF was upregulated to further influence the focal adhesion pathway; on the other hand, PI3K-AKT signaling pathway was regulated, impacting cell motility and survival. Finally, beetles showed negative phototaxis under light exposure.