The physiological state of animals can significantly influence how they interpret and respond to chemical cues. However, whether larval responses to conspecific volatiles are context-dependent remains poorly understood. In this study, we evaluated how nutritional state modulates larval responses to volatile chemical cues in Chilecomadia valdiviana (Lepidoptera: Cossidae) using Y-tube olfactometer bioassays. Larvae were exposed to dodecyl acetate (12:OAc), a compound previously identified in larval secretions, an extract of larval secretions, and a combination of both under fed and fasting conditions. The bioassays included: (1) 12:OAc versus control; (2) larval extract (at 1 and 10 larval equivalents) versus 12:OAc; and (3) extract plus 12:OAc versus control. Nutritional state influenced both overall responsiveness and stimulus preference. Fed larvae exhibited a stronger response to the extract at the higher concentration (10 larval equivalents) than to 12:OAc, whereas short-term fasting (24 h) increased responsiveness to 12:OAc as well as the combined stimuli. However, prolonged fasting (5 days) markedly reduced overall responsiveness and led to avoidance of both 12:OAc and the combination. These results indicate that larval responses to volatile cues are not fixed but are modulated by physiological context and stimulus concentration. Our findings support the notion that chemical signals can function as context-dependent modulators rather than invariant attractants, highlighting the context dependence of larval responses to conspecific volatile cues.
Zygogramma bicolorata is a specialist herbivore used worldwide to control the invasive weed Parthenium hysterophorus. A major concern is that after destroying the target weed, these agents might feed on non-target plants. This study investigates how food deprivation influences cannibalism in Z. bicolorata and whether starvation forces host range expansion. When starved adults were offered host leaves and conspecific eggs, they preferred Parthenium when available. However, as phytophagous food decreased, cannibalism on eggs increased (GLMM: χ2 = 187.34, P < 0.001), with females consuming nearly twice as many eggs as males (4.8 ± 0.3 vs. 2.9 ± 0.3 eggs; P < 0.001). Crowding intensified this; at higher densities, beetles consumed 15.6 ± 0.6 eggs versus 3.8 ± 0.3 at lower densities (P < 0.001). Beetles also preferred injured over healthy conspecifics, being 4.3 times more likely to consume injured eggs (odds ratio = 4.26, P < 0.001). Critically, when deprived of host and exposed to non-host Tagetes sp., beetles did not feed on non-host plants. Instead, they turned to cannibalism, consuming 13.0 ± 0.5 eggs versus 1.2 ± 0.3 eggs with host present (P < 0.001). Predator exposure further intensified cannibalism, with beetles consuming 29.3 ± 1.2 conspecifics versus 16.8 ± 0.8 in controls (P < 0.001). Our findings demonstrate that in laboratory conditions, Z. bicolorata responds to food scarcity by increasing cannibalism, not by expanding host range to non-target plants. Under these controlled conditions, cannibalism appears to serve as a short-term survival strategy that reinforces host specificity. Although these laboratory results cannot be directly generalized to field conditions, they alleviate concerns about non-target feeding in the contexts tested and support continued investigation of this beetle for weed control under natural conditions.
Ambient temperature strongly influences behavioral performance in ectothermic animals. Food-related aggression, as a social interaction centered on a defined and controllable resource, provides an ecologically relevant and experimentally tractable framework for studying conflict. However, how offensive and escape behaviors during such competition vary across thermal conditions and genetic backgrounds remains incompletely understood. Here, we compared food-related competitive behaviors in two laboratory strains of male Drosophila melanogaster, Canton-S and w1118, under two assay temperature conditions. We quantified wing threats, physical contact, and withdrawal behaviors. Overall offensive actions were lower under the cooler assay condition ( 18 °C) than under the warmer assay condition ( 25 °C), but genotype-related differences were most evident under the cooler condition. Under 18 °C, Canton-S males exhibited higher levels of offensive behavior than w1118 males, whereas these genotype differences were less pronounced under 25 °C. Wing threat displays showed relatively weak genotype differences, whereas physical contact behaviors showed clearer condition-associated and genotype-related variation. Locomotor assays revealed genotype-dependent differences under the cooler condition, indicating that the reduced offensive behavior of w1118 males cannot be explained solely by general locomotor suppression. Together, these results suggest that food competition-related behaviors differ between male fruit fly strains across assay conditions, with genotype-related differences being most evident under cooler conditions.
A nymphalid butterfly, Polygonia c-aureum L. (Lepidoptera: Nymphalidae), has distinct seasonal diphenism, known as the summer form and the autumn form, which differ in wing morphology, color, behavior, and physiology. The summer form is non-diapause and begins reproduction shortly after emergence, whereas the autumn form induces adult diapause and reproduces in the spring after overwintering. However, autumn forms have been observed mating before overwintering in the wild, and it is unclear what causes this pre-overwinter mating. In this study, we aimed to clarify the relationship between seasonal form and mating by investigating the effects of photoperiod, age, seasonal form, and sex on courtship and mating behaviors during the adult stage. Summer form males courted females regardless of adult photoperiod (long or short days) or the female's seasonal form, but they rarely mated with autumn form females. Autumn form males courted females, both seasonal forms, under long-day conditions. Under short-day conditions, they rarely courted or mated with either autumn or summer form females. However, a small number (5.1
Biologists have long sought to understand the evolution of diverse lifeforms. Multiple genetically controlled color pattern phenotypes occurring within a species, called color polymorphisms, allow exploration of the multiple balancing selective forces which maintain within-population diversity. Mate choice, through mechanisms like disassortative mating or frequency dependent selection, is one such driving force of color polymorphism maintenance. Courtship behaviors influence mate choice in several insect species and may covary with color phenotype. In the color polymorphic tortoise beetle Chelymorpha alternans, overdominance and differential predation, but not disassortative mating, are suspected to maintain five genetically determined color pattern phenotypes. Additionally, offspring of assortative pairings have lower juvenile fitness but are more fecund. However, courtship behaviors and any link to color are not well documented in C. alternans. We provide further evidence of random mating for color phenotype and demonstrate that while no specific courtship behavior or sequence predicted mating success, the number of distinct courtship behaviors performed significantly predicted the probability of mating. Additionally, assortative pairs copulated for longer durations, possibly as a mechanism for increasing fecundity, as extending mating duration can enhance fertilization and clutch size. Our results demonstrate that sexual selection in C. alternans may operate cryptically, rather than through overt behaviors or phenotypic preferences.
Kriechbaumerella dendrolimi Sheng Zhong, 1986 is a dominant pupal parasitoid of Dendrolimus houi de Lajonquière, 1980, a major defoliating pest afflicting coniferous forests in southern China. The efficiency of mass rearing directly influences its effectiveness in biological control programs. This study investigated reproductive modes, reproductive system anatomy, mating behaviours, and key factors influencing fecundity. Results revealed that K. dendrolimi exhibits both arrhenotokous parthenogenesis and sexual reproduction, with highly significant differences in offspring sex ratios between these reproductive modes (P < 0.001). Males mated an average of 12 times during their lifespan and required 1.94 ± 0.92 courtship attempts per successful copulation. Mean courtship duration was 171.37 ± 115.81 s, while copulation lasted 85.66 ± 21.75 s. Females, in contrast, mated only once during their lifetime. Females possess paired ovaries typically containing 5–7 polytrophic ovarioles per ovary, with a maximum ovarian egg load of 97.3 ± 6.37 eggs per female, indicating a synovigenic reproductive strategy. Temperature, female age, and parasitoid-to-host ratios significantly influenced reproductive output. Adult longevity was highest at 20 °C. Ten-day-old females exhibited the highest parasitism rate (80.71
In sepsid flies, mating behavior is often observed at oviposition sites following oviposition, yet where and when virgin females mate remains largely undocumented. Sepsis fulgens is known to form large swarms away from oviposition substrates, previously hypothesized to be “hibernation phenomena.” Here, I report observations of three large swarms of S. fulgens in June and July in central Iran, where both mating attempts and copulations occurred. When provided with dung dishes near the swarm, gravid females left the swarm, oviposited in the dung, and adult flies emerged from it. Females captured in the swarms predominantly carried primordial or immature eggs, and their egg counts did not differ from those of the minority of swarm females with mature eggs. Additionally, when eggs were small, the ovaries lacked excessive tracheae that would indicate past oviposition. These observations suggest that swarm females were nulliparous. In contrast, females at oviposition and feeding sites (on fresh and old dung) mainly carried mature eggs and had lower total egg counts, consistent with prior oviposition. Laboratory-reared flies spontaneously released a lemony scent similar to that emitted by the swarms during their first week of adulthood, and it could also be induced by gently squeezing the abdomen, especially during the first two weeks. These findings challenge the hypothesis that S. fulgens swarms are related to hibernation. Although mating occurs at swarms, the rarity of copulations and gravid females suggests that mating is also not their only function. The swarms may serve multiple purposes, such as facilitating early mating and enhancing chemical defense via collective scent release.
The flower thrips Frankliniella intonsa is a polyphagous and widely distributed agricultural pest that damages a wide range of crops. To obtain information for behavior-based pest management, we evaluated the behavioral responses of F. intonsa and two predatory bugs, Orius laevigatus and O. minutus, to selected attractants previously identified for western flower thrips (WFT) and to several herbivore-induced plant volatiles (HIPVs) using Y-tube olfactometer assays. The influence of physiological state on the responses of F. intonsa to WFT attractants was examined. Among the tested attractants, behavioral responses of F. intonsa varied with physiological condition, with (1S)-(-)-verbenone and methyl isonicotinate eliciting attraction under specific states. In HIPV assays, methyl salicylate and methyl anthranilate elicited repellency in F. intonsa. Predator responses differed between species: O. laevigatus responded positively to methyl isonicotinate, whereas O. minutus exhibited limited responses to the WFT attractants. Methyl anthranilate elicited positive responses in both predator species. These results indicate that selected semiochemicals differentially influence pest and predator behavior and could be incorporated into integrated pest management strategies. Methyl anthranilate elicited repellency in F. intonsa while attracting Orius predators, suggesting its potential role as a push component by repelling pests while enhancing predator recruitment. In contrast, methyl isonicotinate attracted both F. intonsa and O. laevigatus, indicating its potential use as a pull or aggregation component that may increase predator-prey encounter rates in locations away from protected crops. These findings improve understanding of semiochemical-mediated behavioral interactions between F. intonsa and its predators and can be applied in the pest management.
The combination of chemical stimuli can result in redundant, synergistic or novel effects on animal behavior that may be difficult to predict from studies of single compounds. In the field, I recorded the attraction of Nicrophorus orbicollis, which breeds on a fresh carcass, and the attraction of Silphini beetles, which breed on a carcass in active decay, to chemically-supplemented baits. For single compounds, methyl thiocyanate was the most attractive and dimethyl trisulfide the least for N. orbicollis. The opposite pattern was found for Silphini. Mixtures of compounds were not always additive effects of single compounds. The combination of dimethyl disulfide and dimethyl trisulfide attracted large number of both breeding N. orbicollis and Silphini beetles. There was no evidence that Silphini was affected by methyl thiocyanate. On its own, dimethyl disulfide acted as an attractant to Silphini, but in combination with the preferred dimethyl trisulfide, it was a deterrent. The results suggest that beetles exploiting carcasses during different successional stages of decomposition are responding to different sets of volatiles and that combinations of chemicals can result in non-additive effects on attraction of carrion beetles.
Social insects use a complex blend of pheromones to communicate a range of signals, including alarm cues that warn conspecifics of potential threats. This study investigated the behavioral responses and exploratory activities of three ant species- Oecophylla smaragdina, Odontomachus simillimus, and Diacamma rugosum- in reaction to a natural alarm cue, using an open-field bioassay and automated tracking. Exposure to the alarm signal led to a significant reduction in exploratory behavior in all the three ants Oecophylla smaragdina, Odontomachus simillimus, and Diacamma rugosum, as indicated by decreased locomotion and lower average movement speeds. The smashed body of a single conspecific was sufficient to elicit an alarm response, triggered by a combination of alarm pheromones that could provoke either avoidance or initial attraction. Notably, Oecophylla smaragdina and Diacamma rugosum showed aggressive alarm behavior with attraction to the alarm source, marked by prolonged freezing near the smashed conspecific. However, Oecophylla smaragdina displayed defensive postures and, in some instances, responded with aggressive attacks toward the source of the alarm. Odontomachus simillimus individuals took longer to reach the alarm stimulus, which may indicate avoidance or aversion to the alarm signal. These species-specific behavioral patterns underscore the diversity of alarm response strategies among ants and may reflect ecological or evolutionary adaptations related to predation pressure and colony defence.
Insect parasitism is the result of a sequence of directed searching behaviors by parasitoids from host detection and location to host acceptance and host suitability. Understanding parasitoid foraging strategies is essential for assessing their effectiveness in biological control. Dryinus sinicus (Hymenoptera: Dryinidae) is a major nymphal parasitoid of spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), in its native range in East Asia. As part of the evaluation of this parasitoid as a candidate biological control agent to help manage invasive populations of L. delicatula in the United States, we quantified the foraging behaviors of D. sinicus toward different instars (1st, 2nd, and 3rd instars) of L. delicatula nymphs that are susceptible to attack by D. sinicus. A behavioral catalogue was developed, and behavioral events were recorded with BORIS software. The temporal patterns of behaviors were analyzed and examined by constructing behavioral flow diagrams. Results showed that D. sinicus could attack all three instars of L. delicatula nymphs; attack on the 1st instars led more frequently to host feeding, attack on the 2nd instars more frequently led to successful oviposition, while attack on the 3rd instars resulted in lower successful rates of both oviposition and host-feeding. These findings are discussed in regards to host stage selection by this parasitoid and the potential implications for developing efficient protocols for the rearing, study, and field release of this parasitoid against L. delicatula.
Praying mantises are traditionally investigated for their predatory adaptations and morphological specializations, while their intra-specific communication has received comparatively limited attention, especially outside a few model taxa. Here we report previously undocumented communicative behaviors observed under controlled breeding conditions in three phylogenetically distant species: Parablepharis kuhlii de Haan, 1842, Hymenopus coronatus (Olivier, 1792) and Stagmomantis nahua Saussure, 1869. Repeated observations of both nymphal and adult individuals, supported by video recordings, revealed distinct and structured signaling repertoires expressed during conspecific encounters and pre-copulatory interactions. Documented behaviors include stereotyped abdominal oscillations, rhythmic foreleg and midleg movements, posture modulation, antennal orientation patterns and distance-dependent display adjustments. None of these communicative elements have been previously described for the examined species in the peer-reviewed literature. Notably, several signals were already present in late nymphal stages, suggesting that components of the communicative repertoire may develop prior to sexual maturity. Despite marked differences in ecology, morphology and sexual dimorphism among the three taxa, partially convergent signaling patterns were detected. These findings indicate a more complex and potentially multimodal communication system in Mantodea than traditionally assumed and highlight the value of systematic behavioral observations under controlled conditions in revealing hidden aspects of mantis biology.
Environmental contaminants that influence learning and memory can impact novel resource exploration behaviors; bees, which feed on ephemeral floral resources and must successfully navigate to and from a nest, are particularly vulnerable to such effects. Neonicotinoid pesticides influence learning and memory capabilities in bees, but no study has assessed their impacts on novel resource exploration and its underlying neural genetic processes. We assessed how exposure to field-realistic concentrations of the neonicotinoid imidacloprid impacted novel resource exploration behavior and brain expression levels of genes known to mediate these behaviors in honey bees (Apis mellifera L.). We found few effects of imidacloprid on foraging behaviors, and significant colony interaction effects where they did occur. We find some evidence that exploratory bees exposed to imidacloprid took longer to locate a novel food source. Our gene expression results showed no effects of bee type (exploratory versus non-exploratory) on genes that predicted exploratory foraging behavior in a previous study. However, we did find some evidence that imidacloprid exposure impacted expression of two genes relevant to this phenotype, a glutamate transporter (VGlut) and a glutamate receptor (GluRIB). Our varied effects of imidacloprid exposure are consistent with the broader literature; diverse factors appear to mediate the impacts of this chemical on bee behavior and physiology. Our results suggest imidacloprid may increase the fidelity to a known resource or the willingness to explore novel resources in honey bees, but further studies, including ones in more complex foraging environments, are required to support this hypothesis.
The population ecology and behaviour of the Asian damselfly Platycnemis phyllopoda was studied from 2021 to 2023. The data collected from May to November 2021 in five sites along the shore of Sanchun Lake in the campus of Chongqing Normal University (Chongqing, China), based on counts of unmarked individuals, show that there are two peaks of population density in mid-May and early July, but the flight period extends until mid-October. Males patrol around noon using their swinging fans (enlarged pale-colored tibiae) in a special flight searching for females. Copulations lasted 15.6 ± 8.5 min while oviposition in tandem was observed for several hours. Marking and recapture of 125 males allowed individual recognition, and confirmed that although males of P. phyllopoda are nonterritorial, they nevertheless show high site fidelity. Their survival rate was estimated as 0.857 ± 0.015, with slightly higher survival and recapture rates in mature males compared to young males. We hypothesized that the fans of this species are employed as special signal flags to minimize agonistic encounters with other males by allowing easier sex discrimination. We observed that these enlarged tibiae are also used in courtship to females. By experimentally covering the tibiae of some males with black paint, we found that blackened fans significantly increased the agonistic interactions of patrolling males with other males, but not patrol duration, suggesting that the fans have a key role on male-male encounters. Our study emphasizes the point that, for nonterritorial zygopterans with enlarged tibiae, special patrolling behaviours, either zigzag flight or swinging fans, evolved to avoid unnecessary male-male harassment.
Many insects, including bushcrickets, use acoustic communication for mate finding and mate choice. These signals often produce simultaneous substrate vibrations, potentially aiding localization. However, independently produced vibratory signals are rarely documented in Orthoptera, despite their potential to enhance close-range communication. In the duetting bushcricket Ancistrura nigrovittata, acoustic communication has been extensively studied. We investigated whether any previously overlooked vibratory signals occur during close-range interactions in this species, and characterised their properties and interplay with acoustic signals. Combining laser vibrometry, audio and video recordings, we revealed soundless abdominal tremulation signals in both sexes during partner search and pair formation. Although subtle, these movements produce substrate vibration with amplitudes exceeding those induced by acoustic signalling (stridulation) by an order of magnitude. In both sexes, tremulation and acoustic signals can occur simultaneously or separately, demonstrating independent production mechanisms. Females combine song with tremulation during long-distance calling, use primarily tremulation after a male enters a plant, and typically cease signalling upon being found. Males add tremulation to the song after entering a plant and use it as the primary signal after partner contact. In both sexes, tremulation comprises mostly grouped pulses, emitted at a rate of about 2.5 Hz. Male tremulation exhibits a lower pulse number per train, higher dominant frequencies and amplitudes than female tremulation, and is typically accompanied by a short acoustic tick at the beginning of each pulse. Our findings reveal a previously unknown complexity of vibroacoustic communication in A. nigrovittata.
Many animals engage in rescue behavior. Rescue in social species is particularly interesting, because multiple individuals work together to coordinate rescue activities. This study investigates genetic effects on rescue behavior in the fire ant Solenopsis invicta. We determined if S. invicta workers who assisted in cooperative rescue of brood differed genetically from those who did not. We elicited rescue of brood in the lab by burying larvae in a sand-like substrate, imitating the potential result of a brood chamber collapse. We genotyped rescuers and non-rescuers at variable DNA microsatellite markers to understand the relationships among rescuers, non-rescuers, and the rescued larvae. We found significant genetic differentiation between rescuers and non-rescuers. These results suggest that genotype is a contributing factor in how social groups allocate individuals for rescue activity. Additionally, we genotyped individuals at a genetic marker linked to the S. invicta supergene, which dictates many aspects of social function. Overall, we did not find evidence for an effect of the supergene on rescue participation. Furthermore, genotyping of the buried larval targets enabled us to investigate nepotism and green-beard effects. However, we did not find evidence for either. Overall, our data provide evidence for an underlying genetic basis to an altruistic social behavior. Our results further our understanding of the genetic mechanisms underlying important group behaviors in societies.
The adaptive timing of hatching is important for successful brood parasitism in some birds and insects. Parental burying beetles typically rear their own larvae on carcasses, but occasionally raise brood-parasitic larvae from the eggs of other females (“egg dumping”). Parasitic eggs must hatch synchronously with host eggs because the host parents indiscriminately accept any larvae during that period. If eggs hatch too early, parasitic larvae are eliminated by the host parents; if they hatch too late, they are outcompeted by the host’s own larvae. Therefore, synchronous hatching is critical for brood parasites. However, the conditions under which this synchronization is achieved remain unclear. Furthermore, it has yet to be established whether the hatching of parasitic larvae synchronizes with that of host larvae even when the reproductive behavior of the parasite lags behind that of the host. In the burying beetle Nicrophorus quadripunctatus Kraatz, we observed the hatching of host and parasite offspring under experimental conditions in which female parasites (intruders) encountered carcasses secured by female hosts (residents) two days earlier. In 14 of the 40 replicates, “winning” residents laid 36 eggs, and “defeated” intruders laid six “dumped eggs” on average. The hatching of intruder offspring synchronized with that of resident offspring despite the two-day lag, suggesting that egg dumping leads to brood parasitism. Notably, the period from contact with carcasses to hatching was significantly shorter for intruders than for residents. Therefore, the timing of hatching may contribute to the success of brood parasitism.
In temperate regions, paper wasp gynes (Polistes dominula) move to protected shelters in late autumn for the purpose of overwintering. Overwintering represents an energetic challenge for insects, which require sufficient energy reserves to survive the cold season. The aggregation behavior exhibited by overwintering insects is associated with a number of benefits, including the buffering of temperature fluctuations and low humidity. This, in turn, has the effect of reducing desiccation stress and improving overwintering success by reducing energetic costs. The metabolic rates of individual insects can vary between separated individuals and aggregations, with a decline in metabolic rate observed within larger groups. We investigated the metabolism of paper wasp gynes in order to detect energy savings during overwintering. We measured the CO2 production (measure of energy use) of single wasps and aggregations of wasps at three different temperatures (4, 8, 12 °C). Evidence suggests a close relationship between metabolism and locomotor activity; therefore, activity observations were made during the course of experiments. Metabolic rate increased with ambient temperature in a typical exponential course in both singles and aggregations. However, in contrast to the findings of other studies, no difference in metabolism was observed between singles and aggregations. Furthermore, activity scores revealed higher activity levels in aggregations. This indicates that energetic requirements are not the underlying cause of the aggregation behavior exhibited by overwintering paper wasp gynes.
Male crickets transfer sperm via a spermatophore, which also contains compounds that enhance ovulation, egg hatching, and the female's longevity. These compounds also may induce mechanisms to guarantee males' paternity. In Macroanaxipha macilenta (Saussure, 1897), there are two male morphs, the Wide-Forewing, and the Narrow-Forewing. During mating, Wide-Forewing males transfer one spermatophore to the female, whereas Narrow-Forewing males transfer two. We analyzed the effects of spermatophores on the fecundity and lifespan of females mated with Wide-Forewing and Narrow-Forewing males. While both types of spermatophores contain sperm, reproductive success varied between the two groups. We found that 41.37% of the females mated with Wide-Forewing and 30.46% of the females mated with Narrow-Forewing males had offspring. The study shows that while spermatophore consumption does not affect fecundity. Moreover, females mated with Narrow-Forewing males had a longer lifespan than females mated with Wide-Forewing males. Our results suggest that Wide-Forewing and Narrow-Forewing males might represent alternative mating tactics with different payoffs.
Animals undergo numerous modifications in behavior, physiology and morphology as they transition from a nonbreeding to a breeding state. With their rapid and repeated breeding cycles, burying beetles can be a model system for the study of how temporal phenotypic plasticity is used to cope with changing stressors. In this study, we investigated how the function of anal secretions of Nicrophorus orbicollis are altered by the onset of breeding. Larvae of Ptomascopus morio, a related carrion feeder that does not have parent–offspring feedings, were used as test subjects for N. orbicollis secretions. Newly eclosed larvae were fed one of six diets: anal secretions of nonbreeding female or male N. orbicollis, anal secretions of breeding females or males, oral secretions of female N. orbicollis, or macerated chicken liver. Survival of larvae was greater on anal secretions of breeders than with nonbreeders; survival was also high with oral secretions from breeding females and on liver. Growth was very poor with anal secretions compared to either oral secretions or liver, suggesting that while anal secretions are modified during parental care to be less toxic to young, they provide little or no nutritional benefit.
