Nonconsumptive Harmonia axyridis (Coleoptera: Coccinellidae) induces stage-dependent dispersal, development, and diapause investment in Periphyllus koelreuteriae (Hemiptera: Chaitophoridae)

Abstract

In predator–prey systems, nonconsumptive effects can influence prey behavior and physiological states. Prey encountering enemies exhibit adaptive responses to reduce predation risk, with these responses often tied to their current life stages. Here, we experimentally investigated the adaptive changes in Periphyllus koelreuteriae (Takahashi) across different life stages in response to short-term exposure to the nonfeeding Harmonia axyridis (Pallas) in the laboratory, focusing on aphid dispersion, development, and fecundity. Upon receiving signals from H. axyridis, aphids at all instars except the early nymphs (first instar and second instar) showed enhanced dispersal ability, with antipredatory dispersion intensifying as either ladybeetles or aphids matured. When facing predation risk, aphid nymphs respond by prolonging the developmental duration of their current instar, and once the risk is eliminated, the nymphs resume normal development. Furthermore, shortened adult longevity is observed only in the fourth-instar nymphs and adults, which reduces the total lifespan, whereas the lifespan of the first- to third-instar nymphs remains unchanged. In addition, fourth-instar nymphs and adults, facing predation risk, significantly decreased reproductive output and had a higher proportion of diapause offspring. This study demonstrates that transient predation pressure from H. axyridis induces stage-dependent adaptive changes in aphid populations, including enhanced dispersal, prolonged preadult duration, and reduced fecundity. The results provide insights for optimizing biological control of aphid populations using predatory ladybeetles.

Graphical abstract

Graphical Abstract.

Introduction

Predator–prey relationships are ubiquitous in nature, and food webs formed by predator–prey interactions can exert cascading effects on the properties and functions of ecosystem (Schmitz 2008). Predators are not only able to consume prey directly through lethal predation (consumptive effects) but also to regulate prey populations by influencing prey fitness through “startle” (nonconsumptive effects or predation risk) (Lee et al. 2014). Although predation risk is not directly lethal, it induces changes in prey behavior and physiology that ultimately lead to reduced reproductive success and limited population growth (Creel et al. 2007, Sheriff et al. 2011, Peacor et al. 2013). Studies have shown that the modulatory effects of nonconsumptive effects on prey population dynamics can occasionally outweigh the direct lethal effects of predation (Peacor and Werner 2004, Preisser et al. 2005). Much of the previous biological control research has focused on the direct lethal effects of predators (Sih et al. 1985), and as our understanding of ecology expands, more and more studies are demonstrating the value of the nonlethal effects of predators in regulating pest population dynamics (Buchanan et al. 2017, Culshaw‐Maurer et al. 2020). Therefore, a detailed understanding of the impact of predation risk on prey is crucial for us to more accurately assess the effectiveness of predators. It also facilitates further exploration of the mechanisms of predator–prey interactions.

Predation risk causes prey to adopt antipredation strategies in response to predation pressure, thereby reducing the likelihood of detection and being killed by predators (Harvell 1990, Agrawal 2001). This defensive strategy usually leads to changes in behavioral responses, developmental progress, morphological characteristics, and resource allocation in the prey (Peckarsky et al. 2008, Zuharah et al. 2015, Buchanan et al. 2017). For example, when predation pressure is detected, Bemisia argentifolii reduces damage to the lower parts of the plant and migrates to the apical plant tissues to avoid the predatory Delphastus catalinae (Lee et al. 2014). The fruit fly Drosophila melanogaster exhibits different degrees of developmental acceleration in response to stress imposed by the generalist predator Propylea japonica (Li and Ge 2010). The chemical cues from predators delay the development of the mosquito Culex pipiens which in turn results in reduced body size of adults (Beketov and Liess 2007). Upon perceiving the presence of aquatic predators, Ischnura cervula shifts its attention from foraging to predator detection and reduces its investment in feeding behavior (Siepielski et al. 2016).

Animals adopt distinct survival strategies in response to both environmental cues and physiological states, a fundamental tradeoff universally observed in predator–prey interactions (McNamara and Houston 1990, Tigreros et al. 2018). In arthropods, prey responses to predation risk are modulated by multifaceted factors, including natural enemy traits and prey attributes (Ramirez et al. 2010, Wei et al. 2023). The phytophagous mite Tyrophagus putrescentiae exhibits stage-dependent responses to predation risk from Neoseiulus cucumeris, with distinct impacts observed across its developmental instars (Wei et al. 2023). Pea aphids under predation threat exhibit a faster developmental rate of cornicles during the first four instars than in the adult stage (Mondor and Roitberg 2002). Ladybeetles exert significantly stronger deterrence effects on younger instars of Helicoverpa armigera than on older ones (Yan et al. 2017). Prey at different developmental stages may employ distinct defensive strategies owing to variations in physiological states, resource requirements, and developmental priorities, which ultimately shape prey population density.

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), is a well-known generalist predator. As a natural enemy of various pest species, this predatory insect is known to suppress outbreaks of many arthropods, resulting in significant impacts on agriculture and forestry through lethal consumption (Koch 2003). Moreover, due to its high adaptability, broad diet, and strong predation capacity, H. axyridis serves as a promising biocontrol agent in cropping systems (Finlayson et al. 2010, Wu et al. 2025).

Periphyllus koelreuteriae (Takahashi) is a key pest of Koelreuteria bipinnata Franch (Sapindaceae: Koelreuteria), an avenue tree species in East Asia (Li et al. 2015). These aphids primarily feed on tender parts of trees, including buds, young leaves, and shoots, which can cause leaf curling, deformation, shoot growth stagnation, and even withering and death of branches and leaves in severe cases. Additionally, the aphid secretes abundant honeydew, compromising landscape aesthetics. In China, P. koelreuteriae overwinters as fertilized eggs in bark crevices and branch forks (Wang et al. 1990). Eggs hatch in early spring of the following year, leading to continuous damage to K. bipinnata from March to May. Diapause nymphs emerge in late April, over-summer as first-instar diapause nymphs after mid-May, which differ significantly from normal aphids in appearance and behavior: diapause individuals are transparent, neither feeding nor moving, and stay at the edges of leaves, while normal ones have black speckles and are active feeders. Diapause is terminated and activity resumes in early September, with egg-laying for overwintering occurring in mid-November (Li et al. 2015). Currently, chemical control remains the primary management strategy for this aphid. However, long-term pesticide use not only accelerates the development of pesticide resistance in P. koelreuteriae but also causes environmental pollution and endangers human health. As a natural predator of P. koelreuteriae, using ladybeetles to control aphid populations represents a promising alternative to pesticide-based control (Che et al. 2024). However, the effects of predation risk from H. axyridis on P. koelreuteriae have not been reported. Given that aphid populations reproduce rapidly and often cause persistent damage to plants in the wild due to overlapping generations, to enhance the efficacy of biocontrol, it is necessary to understand the impact of predation risk on P. koelreuteriae at different life stages, thereby maximizing the role of ladybeetles in aphid control.

We investigated the effects of predation risk from H. axyridis on dispersal, development, and reproduction across different life stages (first to fourth instar nymphs and adults) of P. koelreuteriae. Meanwhile, to explore the transgenerational effects of predation pressure on the morphological traits, we recorded the proportion of diapausing aphids in offspring. By establishing an impaired-predator environment where predators were present but unable to directly consume prey, we imposed perceived predation risk on the prey to explore their responses to the nonconsumptive effects of predatory enemies (Thaler et al. 2012, Kersch‐Becker and Thaler 2015). The results reveal the defensive strategies of P. koelreuteriae at different instars in response to short-term predation risk from H. axyridis, contributing to a more comprehensive evaluation of ladybeetle-mediated aphid population regulation and providing new insights for the biocontrol of aphid outbreaks.

Materials and Methods

Plants and Insects

P. koelreuteriae were collected from K. bipinnata trees along the campus avenues of Henan University of Science and Technology (34°36′N, 112°25′E) in Luoyang, Henan Province, China. One-to 2-year-old branches were excised, cut into 20-cm segments, and inserted into 20 mm × 120 mm test tubes filled with distilled water. Test tubes were vertically positioned in a rack within a growth chamber (PQX-450B-30H, Ningbo Laifu Technology Co., Ltd) under controlled conditions: 23 ± 1 °C, 60%±5% relative humidity (RH), and a 15L:9D photoperiod. Branches with emerging tender buds were used for aphid rearing, with periodic replacements based on bud development. The tested aphids included 5 groups: first- to fourth-instar nymphs (first-instar nymphs: N1; second-instar nymphs: N2; third-instar nymphs: N3; fourth-instar nymphs: N4) and adults.

H. axyridis adults were collected from campus rapeseed fields in early April and reared in plastic containers (13.7 cm × 8.2 cm × 5.3 cm) at ambient temperature. Considering that ladybeetles are generalist predators that feed on a variety of aphid species in natural habitats, they were provided with a mixed diet of P. koelreuteri, Myzus persicae, and Cinara tujafilina. To preserve their wild predatory behavior and vitality, different aphid species were replenished twice daily (morning and evening) to ensure dietary diversity. In experiments testing the effect of risk on aphid dispersal, we used H. axyridis first to fourth instar larvae (first-instar larvae: L1; second-instar larvae: L2; third-instar larvae: L3; fourth-instar larvae: L4) and adults. In experiments testing the effect of risk on aphid development and reproduction, we used H. axyridis adults.

Effects of H. axyridis Predation Risk on Aphid Dispersal

The experiment was conducted on hydroponically cultured branches of K. bipinnata. Twenty-centimeters long leafy branches were cut, with excess leaves removed to retain 4 alternate leaves. Leaves were washed with distilled water, and the branches were inserted into 100-ml conical flasks filled with water, secured with sponge stoppers. A white circular hardboard (10 cm in diameter) was placed at the top of each flask.

Fifteen nymphs of a specific instar were selected from the aphid colony and placed on leaves, where they were allowed to settle for 30 min. Healthy H. axyridis first to fourth instar larvae and adults were chilled in a freezer for 3 min until comatose, after which more than two-thirds of their mandibles were excised with a scalpel. These modified ladybeetles retained mobility but lacked predatory ability, with 1 individual placed at the base of each branch. The experimental procedures were performed according to the method described by a previous study (Yang et al. 2025). A cylindrical transparent plastic cover (height: 25 cm, diameter: 10 cm) was then placed over the hydroponic branch (Fig. 1A). Aphids that disperse in response to predation pressure from ladybeetles can freely drop from the branches onto the hardboard. After 4 h of ladybeetle exposure, the number of aphids on the hardboard (dispersed individuals) was recorded. For adult aphid dispersal assays, 7 adult aphids were placed per branch. Controls lacked ladybeetles under identical conditions. Aphids at each developmental stage were exposed to ladybeetles of each developmental stage. Each treatment was replicated 5 times under controlled conditions: 23 ± 1 °C, 60%±5% RH, and a 15L:9D photoperiod.

Fig. 1.

The experimental setup to test effects of predation risk from Harmonia axyridis on aphid dispersal (A), development and reproduction (B). Created with BioGDP.com.

Effects of H. axyridis Predation Risk on Aphid Development and Reproduction

The experiment was conducted in Petri dishes containing solidified 1% agar. Fresh K. bipinnata leaves were placed adaxial side down on the agar surface. Using a fine brush, a single adult aphid was transferred onto the leaf back. After 6 h (allowing for the production of 3 to 5 nymphs), the adult and excess nymphs were removed, leaving 3 newly born nymphs per dish. One mandible-excised H. axyridis adult was introduced into each dish for a 4-h predation risk exposure and then removed (Fig. 1B). This procedure was repeated for second, third, and fourth instar nymphs, as well as adult aphids. For the control group, 3 aphids at specific developmental stages were also placed in a Petri dish without ladybeetle for 4 h. Treated aphids were then transferred individually to new Petri dishes. The development and survival of each individual were recorded at 12 h intervals. After adult emergence, reproduction (daily nymph production and the number of diapause nymphs among offspring over the first 6 d) and adult longevity were recorded after adult emergence. Each treatment included at least 30 replicates. Environmental conditions were maintained at 23 ± 1 °C, 60 ± 5% RH, and a 15L:9D photoperiod.

Statistical Analysis

Normality and homogeneity of variance were tested using the Shapiro–Wilk test and Levene’s test, respectively. Aphid dispersal rates and offspring diapause rates were arcsine square root-transformed to meet normality assumptions, and aphid daily production data were analyzed by 1-way analysis of variance (ANOVA) followed by Tukey’s honestly significant difference (HSD) post hoc test. Survival analysis was conducted on the developmental duration of aphids, and we used the Cox proportional hazard model with package “survival” (Therneau 2024) to evaluate the effects of stress treatments at different instars on the survival time of aphids, while survival curves were plotted using the Kaplan–Meier method. A linear mixed model (LMM) was employed to analyze the effects of stress treatments and time on aphid fecundity. Both the survival analysis and the LMM were performed in R version 4.4.0 (R Core Team 2024).

Results

The Impact of Predation Risk on Aphid Dispersal

The impact of H. axyridis on the dispersal of P. koelreuteri was contingent on the developmental stages of both predator and prey (Table 1). Specifically, the first-instar nymphs (N1) and second-instar nymphs (N2) showed no significant response to ladybeetle stress (N1: F₅,₂₄=2.20, P =0.088; N2: F₅,₂₄=2.39, P =0.068). In contrast, the third-instar nymphs (N3), fourth-instar nymphs (N4), and adult aphids exhibited significantly elevated dispersal rates as ladybeetle maturity increased (N3: F₅,₂₄=11.02, P <0.001; N4: F₅,₂₄=5.98, P <0.001; adult: F₅,₂₄=8.38, P <0.001). Under stress from ladybeetles at the same developmental stage, aphid dispersal rates increased significantly as the aphids matured (L1: F₅,₂₄=16.25, P <0.001; L2: F₅,₂₄=5.61, P =0.003; L3: F₅,₂₄=22.09, P <0.001; L4: F₅,₂₄=15.03, P <0.001; adult: F₅,₂₄=23.27, P <0.001).

Table 1.

Effects of different stages of Harmonia axyridis (N = 5 per treatment group) on dispersal of various instars of Periphyllus koelreuteriae (N = 35 for adult aphids; N = 75 for other aphid instars per treatment group)

Treatment	Proportion of aphids that dispersed (%)
	Aphid N1	Aphid N2	Aphid N3	Aphid N4	Aphid adults
CK	0.00±0.00aA	1.33±1.33aA	2.67±1.63cA	4.00±1.63bA	8.57±3.50cA
Ladybeetle L1	1.33±1.33aC	2.67±1.63aC	14.67±1.33bcB	16.00±3.40abB	28.57±4.52bcA
Ladybeetle L2	4.00±1.63aC	5.33±2.49aC	17.33±2.67abAB	18.67±4.90abAB	34.29±9.69abcA
Ladybeetle L3	6.67±2.11aC	6.67±2.11aC	20.00±2.98abBC	22.67±3.40aB	45.71±5.35abA
Ladybeetle L4	6.67±2.98aC	8.00±2.49aC	25.33±2.49abBC	30.67±6.18aB	51.43±7.28abA
Ladybeetle adult	8.00±3.27aC	9.33±1.63aC	29.33±4.52aB	32.00±4.42aB	62.86±7.28aA

Different lowercase letters in the same column indicate significant differences; different uppercase letters in the same row indicate significant differences (Tukey’s HSD, P <0.05). Abbreviation: CK, control.

N1: 1st-instar nymphs; N2: 2nd-instar nymphs; N3: 3rd-instar nymphs; N4: 4th-instar nymphs; L1: 1st-instar larvae; L2: 2nd-instar larvae; L3: 3rd-instar larvae; L4: 4th-instar larvae.

The Impact of Predation Risk on the Lifespan and Developmental Time of Aphids

The lifespan of P. koelreuteriae is affected by ladybeetle-induced stress, and the extent of this effect is related to the instar at which the aphids are exposed to predation stress (Fig. 2). In the predation risk experiment, the lifespan of fourth-instar nymphs and adult aphids was significantly shortened. When exposed to ladybeetle stress, the median survival time of fourth-instar nymphs and adult aphids was 16 and 14.5 d, respectively, which were significantly shorter than that of the control group (17.5 d) (Supplementary Table S1). In contrast, the median survival time of the stress in first-, second-, and third-instar nymphs showed no significant difference from that of the control group.

Fig. 2.

The lifespan of Periphyllus koelreuteriae at different instars when exposed to predator stress. Curves were fitted using log-rank test. Abbreviation: CK, control ; N1: 1st-instar nymphs; N2: 2nd-instar nymphs; N3: 3rd-instar nymphs; N4: 4th-instar nymphs.

The developmental duration of aphids at different stages after exposure to stress showed that predation pressure caused first-instar, second-instar, and third-instar nymphs to delay their current developmental stage, but did not affect their subsequent development or adult longevity. In contrast, for fourth-instar nymphs and adults, predation risk significantly shortened their adult longevity (Supplementary Fig. S1).

The Impact of Predation Risk on Aphid Production

The fecundity of adult P. koelreuteriae is significantly affected by the instars exposed to stress, time, and their interaction. Similarly, the fecundity of fourth-instar aphids is also significantly influenced by the aforementioned factors (instars exposed to stress, time), but not by the interaction between these 2 factors (Supplementary Table S2). The fecundity of fourth-instar nymphs and adult aphids exposed to predation risk was lower than that of the control group (Fig. 3).

Fig. 3.

The fecundity of Periphyllus koelreuteriae at different instars when exposed to predator stress. Predicted curves were fitted using linear mixed models. Abbreviation: CK, control ; N1: 1st-instar nymphs; N2: 2nd-instar nymphs; N3: 3rd-instar nymphs; N4: 4th-instar nymphs.

Analysis of daily production showed that, compared with the control, the production by fourth-instar nymphs and adults under stress was significantly lower during the first 5 d (day 1: F_5,63 = 11.36, P < 0.001; day 2: F_5,63 = 16.92, P < 0.001; day 3: F_5,63 = 6.56, P < 0.001; day 4: F_5,63 = 5.50, P < 0.001; day 5: F_5,63 = 3.32, P < 0.001). By the sixth day, their production no longer differed from that of the control group (F_5,63 = 1.10, P = 0.367) (Fig. 4).

Fig. 4.

Daily reproduction output of aphids at different developmental stages exposed to predation risk. *P <0.05; **P <0.01 (Tukey’s HSD). Abbreviations: CK, control; n.s. not significant ; N1: 1st-instar nymphs; N2: 2nd-instar nymphs; N3: 3rd-instar nymphs; N4: 4th-instar nymphs.

The Impacts of Predation Risk on the Proportion of Diapause Offspring in Aphids

There were significant differences in the proportion of diapause offspring among aphids at different developmental stages after exposure to predation risk (F_5,63 = 31.65, P  < 0.001). In general, the more mature the aphids exposed to predation risk, the higher the proportion of diapause offspring produced. When first- to third-instar nymphs were exposed to predation risk, their diapause offspring ratios did not differ from those of the control group. However, when fourth-instar nymphs and adult aphids were exposed to predation risk, their diapause offspring ratios were significantly higher than those of the control and first- to third-instar nymph groups (Fig. 5).

Fig. 5.

Proportion of diapause offspring of aphids at different developmental stages exposed to predation risk. Different letters above the bars indicate significant differences between different treatments (P <0.05), based on the result of Tukey’s HSD. Abbreviation: CK, control ; N1: 1st-instar nymphs; N2: 2nd-instar nymphs; N3: 3rd-instar nymphs; N4: 4th-instar nymphs.

Daily analysis of diapause offspring proportion revealed that, compared with the control group, aphids at all developmental stages under stress showed no difference in diapause proportion on day 1 (F_5,63 = 0.53, P = 0.755). However, from day 2 onward, the proportion of diapause offspring produced by fourth-instar nymphs and adults under stress was significantly higher than that of the control (day 2: F_5,63 = 2.70, P  = 0.028; day 3: F_5,63 = 15.89, P < 0.001; day 4: F_5,63 = 13.05, P <0.001; day 5: F_5,63=11.00, P <0.001; day 6: F_5,63=5.47, P <0.001) (Fig. 6).

Fig. 6.

Daily proportion of diapause offspring of aphid at different developmental stages exposed to predation risk. *P <0.05; **P <0.01 (Tukey’s HSD). Abbreviations: CK, control; n.s. not significant ; N1: 1st-instar nymphs; N2: 2nd-instar nymphs; N3: 3rd-instar nymphs; N4: 4th-instar nymphs.

Discussion

Previous research demonstrated that olfactory, visual, and tactile signals from H. axyridis induce varying degrees of responses in P. koelreuteria. Compared with single cues, multiple cues exert stronger effects on the aphids (Yang et al. 2025). Thus, the present study further clarifies the changes in P. koelreuteriae across instars in response to predation risk under the combined action of multiple cues. The results of this study demonstrate that in the ladybeetle–aphid interaction system, P. koelreuteri exhibits short-term decision-making in response to predator risk, significantly altering its dispersal capacity, developmental rate, and reproductive output. Predator intimidation causes the dispersal proportion of third-instar and older aphids to increase; furthermore, the more mature either the ladybeetle or the aphid is, the stronger the aphid’s dispersal tendency becomes. Compared with aphids on predator-free plants, individuals under “pseudopredator” treatment delay the development of their current stage; however, only the total developmental time of fourth-instar nymphs and adult aphids changed. Older instars and adults displayed reduced fecundity. These findings suggest a potential linkage between the predation risk imposed by H. axyridis and behavioral plasticity in aphids. Notably, the magnitude of this impact is dependent on the prey stage. Ladybeetles not only compromised the within-generation fitness of P. koelreuteri but also accelerated population decline through transgenerational phenotypic induction. Upon perceiving predatory threats, older nymphs and adults tended to produce a higher proportion of diapause offspring, thereby modulating key population parameters.

Herbivorous insects can proactively adjust their behavior to avoid the temporal and spatial activities of natural enemies, thereby mitigating the risk of enemy encounters (Houston et al. 1993). Sloggett and Weisser (2002) proposed the concept of the “analogous to crowding effect” in aphids, defining it as the phenomenon where aphids perceive adverse conditions as impending “crowding” and flee from their habitat. The typical case involves aphids dispersing from host plants by crawling or dropping to evade predator hunting (Beddington et al. 1978, Kersch‐Becker and Thaler 2015, Humphreys and Ruxton 2019). Our results showed that P. koelreuteri similarly detached from host plants to escape pursuit upon encountering predators, and the degree of antipredator dispersal was related to the life stages of both ladybeetles and aphids. Existing reports indicate that as H. axyridis instars grow, their body size increases, along with the daily maximum predation capacity on P. koelreuteri (Che et al. 2024). Predators with larger body sizes and richer hunting experience impose a greater sense of fear on prey (Dixon 1958, Buchanan et al. 2017), which may drive aphids away from their enemies. Previous studies have shown that young aphids are less inclined to drop from their host plants, instead releasing alarm pheromones in crisis, while older individuals tend to actively escape from predator-present environments (Losey and Denno 1998, Mondor and Roitberg 2002). When facing leaf-foraging predators, N1 and N2 aphids did not adopt more proactive escape strategies, possibly due to the costs of dropping: young aphids have weak mobility, making it difficult to rapidly regain abandoned resources after detaching from the host plants, and dropping often exposes them to more lethal threats on the ground, including desiccation and ground-foraging predators. (Losey and Denno 1998). Older aphids, with stronger mobility, can achieve spatial niche separation from predators through rapid dispersal, then relocate and return to the host plants (Dill et al. 1990).

Predation risk significantly influenced aphid development, although the effect of predation risk persisted only for a limited period. Aphids exposed to impaired predators exhibited prolonged developmental duration, which returned to normal upon relocation to predator-free environments. Under natural enemy stress, prey must tradeoff between energy acquisition and predation avoidance. Our experiments showed that P. koelreuteri prioritized the latter, differing from the choice made by Aphis gossypii when facing ladybeetles. In a study by Li et al. (2014), enclosed predators shortened the preadult stage of A. gossypii. Numerous reports indicate that insects modify their feeding behavior to minimize exposure time within the predator’s visual field, leading to reduced growth and development rates (Hermann and Landis 2017, Culshaw‐Maurer et al. 2020). In addition, alterations in metabolic levels may also account for the delay in developmental duration (Stoks 2001). Interestingly, aphids exhibit a specialized behavior upon detecting danger, releasing alarm pheromones from their cornicles. The production and emission of alarm pheromones incur substantial energetic costs, thereby limiting aphid growth and development (Vandermoten et al. 2012).

Previous studies have shown that under predation risk, prey exhibit a tradeoff between responding to predatory threats and maintaining their longevity (Duong and McCauley 2016, Schwenke et al. 2016). In the present study, fourth-instar nymphs and adult aphids exhibit reduced lifespan when exposed to predation risk. This result is consistent with previous findings. As predation pressure increases, the larval developmental duration of T. putrescentiae shortens, and adult longevity also decreases (Wei and Zhang 2022). Spodoptera litura similarly shows reduced longevity under bat predation risk (Zhang et al. 2023). Prolonged exposure to the predatory threat of Menochilus sexmaculatus significantly shortens the adult longevity of A. gossypii (Lin et al. 2023). Furthermore, adult longevity of Bactrocera dorsalis is reduced when exposed to the predation risk of Hierodula patellifera (Liu et al. 2024). These results suggest that adults accelerate or invest more resources into reproduction under stressful conditions, shortening their lifespan in the process, thereby ensuring population persistence under stressful conditions.

Our results show that the fecundity of aphids in the N4 stage and adults exposed to transient predation pressure was significantly lower than that of predator-free controls. This finding aligns with previous studies indicating reduced fecundity in aphid mothers exposed to predator “threats” (Hermann et al. 2021, Lin et al. 2023). Altered reproductive behavior is a typical response to nonlethal effects (Lima 1998). For example, Tigreros et al. (2019) found that female Colorado potato beetles exposed to predation pressure during the larval stage exhibited reduced lifetime fecundity. Similarly, female spider mites living on leaf disks with prior activity from specialist natural enemies showed reduced daily reproductive output, and female offspring reared under enemy cues also exhibited decreased reproductive investment (Li and Zhang 2019). Additionally, pea aphid populations affected by damsel bugs had lower population growth rates than those in “safe” environments (Nelson et al. 2004). Notably, this reduction in reproductive production output may also stem from changes in parental nutritional status, as predator presence forces aphid mothers to interrupt feeding, with hunger subsequently impacting reproduction (Nelson 2007, Tamai and Choh 2019).

Cues from predation risk can induce organisms to alter offspring morphology, thereby producing progeny with higher adaptive value. This transgenerational phenotypic change is termed maternal-induced defense (Agrawal et al. 1999). Generally, plants tend to endow offspring with defensive traits (Agrawal et al. 1999), while animals tend to produce offspring with behavioral and morphological adaptations (Weisser 2001). Indeed, aphids often reallocate investment in offspring morphology upon physical contact with natural enemies or merely by perceiving their traces, although these trait changes often lead to reduced offspring fecundity. A large body of research shows that natural enemy induction increases the proportion of winged offspring in many aphid strains, including pea aphids, peach aphids and cotton aphids (Weisser et al. 1999, Mondor et al. 2005, Hermann et al. 2021). In this study, aphid mothers under threat from H. axyridis chose to produce a higher proportion of diapause individuals, a result consistent with our expectations. Diapause aphids exhibit small body size, transparent body color, and reduced feeding activity, making them less detectable by leaf-foraging predators compared to normal aphids. Transgenerational effects avoid the lag in induced defenses, potentially providing optimal protection for aphids during early life stages under predation pressure.

Our research only explored the effects of short-term risk on prey development and fecundity. Lin et al. (2023) suggested that cotton aphids exhibit different behavioral responses under predator risk exposure for varying durations (2, 6, or 24 h). Furthermore, chemical, tactile, visual, and other such cues from predators may all trigger vigilance in aphids (Kansman et al. 2023, Yang et al. 2025), and the intensity of these cues was not quantitatively analyzed in our experiment. These pending studies will provide richer evidence for understanding the mechanisms of ladybeetle–aphid interactions, contribute to a more comprehensive evaluation of ladybeetles’ capacity to control aphid populations, and offer new insights for environmentally friendly management of aphids.

Author Contributions

Pinhong Zhu (Conceptualization [equal], Data curation [equal], Formal analysis [equal], Investigation [equal], Methodology [equal], Writing—original draft [equal], Writing—review & editing [equal]), Yue Wang (Conceptualization [equal], Data curation [equal], Formal analysis [equal], Investigation [equal], Methodology [equal], Writing—original draft [equal], Writing—review & editing [equal]), Shien Pang (Data curation [equal], Writing—review & editing [equal]), Shanshan Guo (Formal analysis [equal], Investigation [equal], Methodology [equal]), Mengchao Kong (Formal analysis [equal], Writing—review & editing [equal]), Dingxu Li (Project administration [equal], Supervision [equal], Writing—review & editing [equal]), Dongsheng Li (Conceptualization [equal], Resources [equal], Visualization [equal]), and Haibo Yang (Conceptualization [lead], Funding acquisition [lead], Project administration [lead], Supervision [lead], Writing—review & editing [equal])

Supplementary Material

Supplementary material is available at Journal of Insect Science online.

Funding

This study was financially supported by the Natural Science Foundation of Henan (252300423039), the National Natural Science Foundation of China (31901872) and the Young Backbone Teachers Project of Henan University of Science and Technology (2023).

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.