Nectar vs. pollen loading affects the tradeoff between flight stability and maneuverability in bumblebees

Electrostatic pollination by butterflies and moths

Animals, most notably insects, generally seem to accumulate electrostatic charge in nature. These electrostatic charges will exert forces on other charges in these animals' environments and therefore have the potential to attract or repel other objects, for example, pollen from flowers. Here, we show that butterflies and moths (Lepidoptera) accumulate electrostatic charge while in flight. Then, using finite element analysis, we demonstrate that when within millimetres of a flower, the electrostatic charge of a lepidopteran generates an electric field in excess of 5 kV m-1, and that an electric field of this magnitude is sufficient to elicit contactless pollen transfer from flowers across air gaps onto the body of a butterfly or moth. Furthermore, we see that phylogenetic variations exist in the magnitude and polarity of net charge between different species and families and Lepidoptera. These phylogenetic variations in electrostatic charging correlate with morphological, biogeographical and ecological differences between different clades. Such correlations with biogeographical and ecological differences may reflect evolutionary adaptations towards maximizing or minimizing charge accumulation, in relation to pollination, predation and parasitism, and thus we introduce the idea that electrostatic charging may be a trait upon which evolution can act.

Bumblebees compensate for the adverse effects of sidewind during visually guided landings

Flying animals often encounter winds during visually guided landings. However, how winds affect their flight control strategy during landing is unknown. Here, we investigated how sidewind affects the landing performance and sensorimotor control of foraging bumblebees (Bombus terrestris). We trained bumblebees to forage in a wind tunnel, and used high-speed stereoscopic videography to record 19,421 landing maneuvers in six sidewind speeds (0 to 3.4 m s-1), which correspond to winds encountered in nature. Bumblebees landed less often in higher windspeeds, but the landing durations from free flight were not increased by wind. By testing how bumblebees adjusted their landing control to compensate for adverse effects of sidewind on landing, we showed that the landing strategy in sidewind resembled that in still air, but with important adaptations. Bumblebees landing in a sidewind tended to drift downwind, which they controlled for by performing more hover maneuvers. Surprisingly, the increased hover prevalence did not increase the duration of free-flight landing maneuvers, as these bumblebees flew faster towards the landing platform outside the hover phases. Hence, by alternating these two flight modes along their flight path, free-flying bumblebees negated the adverse effects of high windspeeds on landing duration. Using control theory, we hypothesize that bumblebees achieve this by integrating a combination of direct aerodynamic feedback and a wind-mediated mechanosensory feedback control, with their vision-based sensorimotor control loop. The revealed landing strategy may be commonly used by insects landing in windy conditions, and may inspire the development of landing control strategies onboard autonomously flying robots.

We know very little about pollination in the Platanthera Rich (Orchidaceae: Orchidoideae)

The Platanthera Rich. (Orchidoideae) comprise a speciose genus of orchids primarily in the northern hemisphere, with up to 200 known species worldwide. Individual species are known to self-pollinate, but many rely on insect pollinators with characteristics such as floral color, timing of floral odor emissions, nectar rewards, and spur length associated with particular pollination syndromes. As with many orchids, some orchid-pollinator associations are likely highly co-evolved, but we also know that some Platanthera spp. are the result of hybridization events, which implies a lack of pollinator fidelity in some cases. Some Platanthera spp. occur in large numbers which, coupled with the numerous Platanthera-pollinator systems, make them accessible as study species and useful for co-evolutionary studies. Due to the likely effects of climate change and ongoing development on Platanthera spp. habitats, these orchids and their associated pollinators should be a focus of conservation attention and management. However, while there is a fairly substantial literature coverage of Platanthera-pollinator occurrence and interactions, there are still wide gaps in our understanding of the species involved in these systems. In this systematic review, we outline what is current knowledge and provide guidance on further research that will increase our understanding of orchid-insect co-evolutionary relationships. Our review covers 157 orchid species and about 233 pollinator species interacting with 30 Platanthera spp. We provide analyses on aspects of these interactions such as flower morphology, known insect partners of Platanthera species, insect-Platanthera specificity, pollination visitor timing (diurnal vs. nocturnal), floral rewards, and insect behavior affecting pollination outcomes (e.g., pollinia placement). A substantial number of Platanthera spp. and at least a few of their known pollinators are of official (IUCN) conservation concern - and many of their pollinators remain unassessed or even currently unknown - which adds to the urgency of further research on these co-evolved relationships.

Drosophila flying in augmented reality reveals the vision-based control autonomy of the optomotor response

For walking, swimming, and flying animals, the optomotor response is essential to stabilize gaze. How flexible is the optomotor response? Classic work in Drosophila has argued that flies adapt flight control under augmented visual feedback conditions during goal-directed bar fixation. However, whether the lower-level, reflexive optomotor response can similarly adapt to augmented visual feedback (partially autonomous) or not (autonomous) over long timescales is poorly understood. To address this question, we developed an augmented reality paradigm to study the vision-based control autonomy of the yaw optomotor response of flying fruit flies (Drosophila). Flies were placed in a flight simulator, which permitted free body rotation about the yaw axis. By feeding back body movements in real time to a visual display, we augmented and inverted visual feedback. Thus, this experimental paradigm caused a constant visual error between expected and actual visual feedback to study potential adaptive visuomotor control. By combining experiments with control theory, we demonstrate that the optomotor response is autonomous during augmented reality flight bouts of up to 30 min, which exceeds the reported learning epoch during bar fixation. Agreement between predictions from linear systems theory and experimental data supports the notion that the optomotor response is approximately linear and time invariant within our experimental assay. Even under positive visual feedback, which revealed the stability limit of flies in augmented reality, the optomotor response was autonomous. Our results support a hierarchical motor control architecture in flies with fast and autonomous reflexes at the bottom and more flexible behavior at higher levels.

Selection despite low genetic diversity and high gene flow in a rapid island invasion of the bumblebee, Bombus terrestris

Invasive species are predicted to adjust their morphological, physiological and life-history traits to adapt to their non-native environments. Although a loss of genetic variation during invasion may restrict local adaptation, introduced species often thrive in novel environments. Despite being founded by just a few individuals, Bombus terrestris (Hymenoptera: Apidae) has in less than 30 years successfully spread across the island of Tasmania (Australia), becoming abundant and competitive with native pollinators. We use RADseq to investigate what neutral and adaptive genetic processes associated with environmental and morphological variation allow B. terrestris to thrive as an invasive species in Tasmania. Given the widespread abundance of B. terrestris, we expected little genetic structure across Tasmania and weak signatures of environmental and morphological selection. We found high gene flow with low genetic diversity, although with significant isolation-by-distance and spatial variation in effective migration rates. Restricted migration was evident across the mid-central region of Tasmania, corresponding to higher elevations, pastural land, low wind speeds and low precipitation seasonality. Tajima's D indicated a recent population expansion extending from the south to the north of the island. Selection signatures were found for loci in relation to precipitation, wind speed and wing loading. Candidate loci were annotated to genes with functions related to cuticle water retention and insect flight muscle stability. Understanding how a genetically impoverished invasive bumblebee has rapidly adapted to a novel island environment provides further understanding about the evolutionary processes that determine successful insect invasions, and the potential for invasive hymenopteran pollinators to spread globally.

Flies adaptively control flight to compensate for added inertia

Animal locomotion is highly adaptive, displaying a large degree of flexibility, yet how this flexibility arises from the integration of mechanics and neural control remains elusive. For instance, animals require flexible strategies to maintain performance as changes in mass or inertia impact stability. Compensatory strategies to mechanical loading are especially critical for animals that rely on flight for survival. To shed light on the capacity and flexibility of flight neuromechanics to mechanical loading, we pushed the performance of fruit flies (Drosophila) near its limit and implemented a control theoretic framework. Flies with added inertia were placed inside a virtual reality arena which permitted free rotation about the vertical (yaw) axis. Adding inertia increased the fly's response time yet had little influence on overall gaze stabilization performance. Flies maintained stability following the addition of inertia by adaptively modulating both visuomotor gain and damping. By contrast, mathematical modelling predicted a significant decrease in gaze stabilization performance. Adding inertia altered saccades, however, flies compensated for the added inertia by increasing saccade torque. Taken together, in response to added inertia flies increase reaction time but maintain flight performance through adaptive neural control. Overall, adding inertia decreases closed-loop flight robustness. Our work highlights the flexibility and capacity of motor control in flight.

An Aerial-Wall Robotic Insect That Can Land, Climb, and Take Off from Vertical Surfaces

Insects that can perform flapping-wing flight, climb on a wall, and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic models. However, very few biomimetic robots can perform complex locomotion tasks that combine the 2 abilities of climbing and flying. Here, we describe an aerial-wall amphibious robot that is self-contained for flying and climbing, and that can seamlessly move between the air and wall. It adopts a flapping/rotor hybrid power layout, which realizes not only efficient and controllable flight in the air but also attachment to, and climbing on, the vertical wall through a synergistic combination of the aerodynamic negative pressure adsorption of the rotor power and a climbing mechanism with bionic adhesion performance. On the basis of the attachment mechanism of insect foot pads, the prepared biomimetic adhesive materials of the robot can be applied to various types of wall surfaces to achieve stable climbing. The longitudinal axis layout design of the rotor dynamics and control strategy realize a unique cross-domain movement during the flying-climbing transition, which has important implications in understanding the takeoff and landing of insects. Moreover, it enables the robot to cross the air-wall boundary in 0.4 s (landing), and cross the wall-air boundary in 0.7 s (taking off). The aerial-wall amphibious robot expands the working space of traditional flying and climbing robots, which can pave the way for future robots that can perform autonomous visual monitoring, human search and rescue, and tracking tasks in complex air-wall environments.

Sensory fusion in the hoverfly righting reflex

We study how falling hoverflies use sensory cues to trigger appropriate roll righting behavior. Before being released in a free fall, flies were placed upside-down with their legs contacting the substrate. The prior leg proprioceptive information about their initial orientation sufficed for the flies to right themselves properly. However, flies also use visual and antennal cues to recover faster and disambiguate sensory conflicts. Surprisingly, in one of the experimental conditions tested, hoverflies flew upside-down while still actively flapping their wings. In all the other conditions, flies were able to right themselves using two roll dynamics: fast ([Formula: see text]50ms) and slow ([Formula: see text]110ms) in the presence of consistent and conflicting cues, respectively. These findings suggest that a nonlinear sensory integration of the three types of sensory cues occurred. A ring attractor model was developed and discussed to account for this cue integration process.

Responses in honeybee and bumblebee activity to changes in weather conditions

Insect pollination, and in particular pollination by bees, is a highly valued ecosystem service that ensures plant reproduction and the production of high-quality crops. Bee activity is known to be influenced by the weather, and as the global climate continues to change, the flying frequency and foraging behaviour of bees may also change. To maximise the benefits of pollination in a changing world, we must first understand how current weather conditions influence the activity of different bee species. This is of particular interest in a country such as Ireland where inclement weather conditions are nominally sub-optimal for foraging. We observed honeybee (Apis mellifera) and buff-tailed bumblebee (Bombus terrestris) activity across a variety of weather conditions at seven apple orchards to determine how four weather variables (temperature, relative humidity, solar radiation, wind) influenced the flight activity of each species. Each orchard contained three honeybee and three bumblebee colonies, and so we were able to observe a colony of each species concurrently in the same weather conditions. Overall, honeybees were more sensitive to changes in weather than bumblebees and could be more predisposed to future changes in within-day weather conditions. Our results indicate bumblebees could compensate for low honeybee activity in inclement conditions, which supports the theory that pollinator diversity provides resilience. This may be particularly important in management of pollinators in crops that flower in the spring when weather is more variable, and to allow varied responses to global climate change.

The forewing of a black cicada Cryptotympana atrata (Hemiptera, Homoptera: Cicadidae): Microscopic structures and mechanical properties

Insects in nature flap their wings to generate lift force and driving torque to adjust their attitude and control stability. An insect wing is a biomaterial composed of flexible membranes and tough veins. In this paper, we study the microscopic structures and mechanical properties of the forewing of the black cicada, Cryptotympana atrata. The thickness of the wing membranes and the diameter of veins varied from the wing root to the tip. The thickness of the wing membranes ranged from 6.0 to 29.9 μm, and the diameter of the wing veins decreased in a gradient from the wing root to the tip, demonstrating that the forewing of the black cicada is a nonuniform biomaterial. The elastic modulus of the membrane near the wing root ranged from 4.45 to 5.03 GPa, which is comparable to that of some industrial membranes. The microstructure of the wing vein exhibited a hollow tubular structure with flocculent structure inside. The "fresh" sample stored more water than the "dry" sample, resulting in a significant difference in the elastic modulus between the fresh and dried veins. The different membrane thicknesses and elastic moduli of the wing veins near the root and tip resulted in varied degrees of deformation on both sides of the flexion line of the forewing during twisting. The measurements of the forewing of the cicada may serve as a guide for selecting airfoil materials for the bionic flapping-wing aircraft and promote the design and manufacture of more durable bionic wings in the future.

Flight-Fecundity Trade-offs: A Possible Mechanistic Link in Plant-Herbivore-Pollinator Systems

Plant-herbivore and plant-pollinator interactions are both well-studied, but largely independent of each other. It has become increasingly recognized, however, that pollination and herbivory interact extensively in nature, with consequences for plant fitness. Here, we explore the idea that trade-offs in investment in insect flight and reproduction may be a mechanistic link between pollination and herbivory. We first provide a general background on trade-offs between flight and fecundity in insects. We then focus on Lepidoptera; larvae are generally herbivores while most adults are pollinators, making them ideal to study these links. Increased allocation of resources to flight, we argue, potentially increases a Lepidopteran insect pollinator's efficiency, resulting in higher plant fitness. In contrast, allocation of resources to reproduction in the same insect species reduces plant fitness, because it leads to an increase in herbivore population size. We examine the sequence of resource pools available to herbivorous Lepidopteran larvae (maternally provided nutrients to the eggs, as well as leaf tissue), and to adults (nectar and nuptial gifts provided by the males to the females), which potentially are pollinators. Last, we discuss how subsequent acquisition and allocation of resources from these pools may alter flight-fecundity trade-offs, with concomitant effects both on pollinator performance and the performance of larval herbivores in the next generation. Allocation decisions at different times during ontogeny translate into costs of herbivory and/or benefits of pollination for plants, mechanistically linking herbivory and pollination.

Size constrains oxygen delivery capacity within but not between bumble bee castes

Bumble bees are eusocial, with distinct worker and queen castes that vary strikingly in size and life-history. The smaller workers rely on energetically-demanding foraging flights to collect resources for rearing brood. Queens can be 3 to 4 times larger than workers, flying only for short periods in fall and again in spring after overwintering underground. These differences between castes in size and life history may be reflected in hypoxia tolerance. When oxygen demand exceeds supply, oxygen delivery to the tissues can be compromised. Previous work revealed hypermetric scaling of tracheal system volume of worker bumble bees (Bombus impatiens); larger workers had much larger tracheal volumes, likely to facilitate oxygen delivery over longer distances. Despite their much larger size, queens had relatively small tracheal volumes, potentially limiting their ability to deliver oxygen and reducing their ability to respond to hypoxia. However, these morphological measurements only indirectly point to differences in respiratory capacity. To directly assess size- and caste-related differences in tolerance to low oxygen, we measured critical PO₂ (P_crit; the ambient oxygen level below which metabolism cannot be maintained) during both rest and flight of worker and queen bumble bees. Queens and workers had similar P_crit values during both rest and flight. However, during flight in oxygen levels near the P_crit, mass-specific metabolic rates declined precipitously with mass both across and within castes, suggesting strong size limitations on oxygen delivery, but only during extreme conditions, when demand is high and supply is low. Together, these data suggest that the comparatively small tracheal systems of queen bumble bees do not limit their ability to deliver oxygen except in extreme conditions; they pay little cost for filling body space with eggs rather than tracheal structures.

Wing Coupling in Bees and Wasps: From the Underlying Science to Bioinspired Engineering

Wing-to-wing coupling mechanisms synchronize motions of insect wings and minimize their aerodynamic interference. Albeit they share the same function, their morphological traits appreciably vary across groups. Here the structure-material-function relationship of wing couplings of nine castes and species of Hymenoptera is investigated. It is shown that the springiness, robustness, and asymmetric behavior augment the functionality of the coupling by reducing stress concentrations and minimizing the impacts of excessive flight forces. A quantitative link is established between morphological variants of the coupling mechanisms and forces to which they are subjected. Inspired by the coupling mechanisms, a rotating-sliding mechanical joint that withstands tension and compression and can also be locked/unlocked is fabricated. This is the first biomimetic research of this type that integrates approaches from biology and engineering.

Wind drives temporal variation in pollinator visitation in a fragmented tropical forest

Wind is a critical factor in the ecology of pollinating insects such as bees. However, the role of wind in determining patterns of bee abundance and floral visitation rates across space and time is not well understood. Orchid bees are an important and diverse group of neotropical pollinators that harvest pollen, nectar and resin from plants. In addition, male orchid bees collect volatile scents that they store in special chambers in their hind legs, and for which the wind-based dispersal of odours may play a particularly crucial role. Here, we take advantage of this specialized scent foraging behaviour to study the effects of wind on orchid bee visitation at scent sources in a fragmented tropical forest ecosystem. Consistent with previous work, forest cover increased orchid bee visitation. In addition, we find that temporal changes in wind speed and turbulence increase visitation to scent stations within sites. These results suggest that the increased dispersal of attractive scents provided by wind and turbulence outweighs any biomechanical or energetic costs that might deter bees from foraging in these conditions. Overall, our results highlight the significance of wind in the ecology of these important pollinators in neotropical forests.

Structure, properties and functions of the forewing-hindwing coupling of honeybees

Worker honeybees (Apis mellifera) are morphologically four-winged, but are functionally dipterous insects. During flight, their fore- and hindwings are coupled by means of the forewing posterior rolled margin (PRM) and hindwing hamuli. Morphological analysis shows that the PRM can be connected to the hamuli, so that the fore- and hindwing are firmly hinged, and can rotate with respect to each other. In the present study, using a combination of scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), we investigate the micromorphology and material composition of the coupling structures on both fore- and hindwings. High-speed filming is utilized to determine the angle variation between the fore- and hindwings in tethered flight. Using sets of two-dimensional (2D) computation fluid dynamic analyses, we further aim to understand the influence of the angle variation on the aerodynamic performance of the coupled wings. The results of the morphological investigations show that both PRM and hamuli are made up of a strongly sclerotized cuticle. The sclerotized hinge-like connection of the coupling structure allows a large angle variation between the wings (135°-235°), so that a change is made from an obtuse angle during the pronation and downstroke to a reflex angle during the supination and upstroke. Our computational results show that in comparison to a model with a rigid coupling hinge, the angle variation of a model having a flexible hinge results in both increased lift and drag with a higher rate of drag increase. This study deepens our understanding of the wing-coupling mechanism and functioning of coupled insect wings.

Comparison of Lactate Dehydrogenase Activity in Hive and Forager Honeybees May Indicate Delayed Onset Muscle Soreness - Preliminary Studies

Active skeletal muscles produce lactate. H+ is generated during lactate neutralization in the Cori cycle, which leads to muscle acidosis and soreness (the so-called Delayed Onset Muscle Soreness, DOMS) in vertebrates. The aim of the study was to determine the activities/concentrations of compounds involved in the Cori cycle in worker and forager bees. Muscles, fat bodies, and hemolymph from 1- and 14-day-old workers and foragers were collected and assayed for the protein, lactate, glucose, NAD+, and NADH concentrations and lactate dehydrogenase (LDH) activity. Both lactate concentration and LDH activity in the hemolymph, muscles, and fat bodies increased with age. The concentrations of NAD+ and NADH in the tissues decreased with ageing/senescence, whereas protein concentrations increased until day 14 of bee's life and then decreased in foragers. The concentration of glucose decreased in the hemolymph and muscles and increased in the fat bodies. Elevated lactate concentrations in foragers may indicate transition from the aerobic to the anaerobic phase and development of metabolic acidosis that may eventually lead to muscle damage/soreness and shorter lifespan. When analyzing flight dynamics, load mass, and bee behavior, changes in the concentrations of Cori cycle compounds should be taken into account.

Role of outstretched forelegs of flying beetles revealed and demonstrated by remote leg stimulation in free flight

In flight, many insects fold their forelegs tightly close to the body, which naturally decreases drag or air resistance. However, flying beetles stretch out their forelegs for some reason. Why do they adopt this posture in flight? Here, we show the role of the stretched forelegs in flight of the beetle Mecynorrhina torquata Using leg motion tracking and electromyography in flight, we found that the forelegs were voluntarily swung clockwise in yaw to induce counter-clockwise rotation of the body for turning left, and vice versa. Furthermore, we demonstrated remote control of left-right turnings in flight by swinging the forelegs via a remote electrical stimulator for the leg muscles. The results and demonstration reveal that the beetle's forelegs play a supplemental role in directional steering during flight.

Bumble bee ecophysiology: integrating the changing environment and the organism

Bumble bees are among the most ecologically and economically important pollinators worldwide, yet many of their populations are being threatened by a suite of interrelated, human-mediated environmental changes. Here, I discuss recent progress in our understanding of bumble bee ecophysiology, including advances related to thermal biology in light of global warming; nutritional biology in the context of declining food resources; and the capacity for bumble bees to exhibit physiological plasticity or adaptations to novel or extreme environments, with reference to their evolutionary history and current biogeography.

Bumblebees minimize control challenges by combining active and passive modes in unsteady winds

The natural wind environment that volant insects encounter is unsteady and highly complex, posing significant flight-control and stability challenges. It is critical to understand the strategies insects employ to safely navigate in natural environments. We combined experiments on free flying bumblebees with high-fidelity numerical simulations and lower-order modeling to identify the mechanics that mediate insect flight in unsteady winds. We trained bumblebees to fly upwind towards an artificial flower in a wind tunnel under steady wind and in a von Kármán street formed in the wake of a cylinder. Analysis revealed that at lower frequencies in both steady and unsteady winds the bees mediated lateral movement with body roll - typical casting motion. Numerical simulations of a bumblebee in similar conditions permitted the separation of the passive and active components of the flight trajectories. Consequently, we derived simple mathematical models that describe these two motion components. Comparison between the free-flying live and modeled bees revealed a novel mechanism that enables bees to passively ride out high-frequency perturbations while performing active maneuvers at lower frequencies. The capacity of maintaining stability by combining passive and active modes at different timescales provides a viable means for animals and machines to tackle the challenges posed by complex airflows.

Advantage of straight walk instability in turning maneuver of multilegged locomotion: a robotics approach

Multilegged locomotion improves the mobility of terrestrial animals and artifacts. Using many legs has advantages, such as the ability to avoid falling and to tolerate leg malfunction. However, many intrinsic degrees of freedom make the motion planning and control difficult, and many contact legs can impede the maneuverability during locomotion. The underlying mechanism for generating agile locomotion using many legs remains unclear from biological and engineering viewpoints. The present study used a centipede-like multilegged robot composed of six body segments and twelve legs. The body segments are passively connected through yaw joints with torsional springs. The dynamic stability of the robot walking in a straight line changes through a supercritical Hopf bifurcation due to the body axis flexibility. We focused on a quick turning task of the robot and quantitatively investigated the relationship between stability and maneuverability in multilegged locomotion by using a simple control strategy. Our experimental results show that the straight walk instability does help the turning maneuver. We discuss the importance and relevance of our findings for biological systems and propose a design principle for a simple control scheme to create maneuverable locomotion of multilegged robots.

Wing flexibility improves bumblebee flight stability

Insect wings do not contain intrinsic musculature to change shape, but rather bend and twist passively during flight. Some insect wings feature flexible joints along their veins that contain patches of resilin, a rubber-like protein. Bumblebee wings exhibit a central resilin joint (1m-cu) that has previously been shown to improve vertical force production during hovering flight. In this study, we artificially stiffened bumblebee (Bombus impatiens) wings in vivo by applying a micro-splint to the 1m-cu joint, and measured the consequences for body stability during forward flight in both laminar and turbulent airflow. In laminar flow, bees with stiffened wings exhibited significantly higher mean rotation rates and standard deviation of orientation about the roll axis. Decreasing the wing’s flexibility significantly increased its projected surface area relative to the oncoming airflow, likely increasing the drag force it experienced during particular phases of the wingstroke. We hypothesize that higher drag forces on stiffened wings decrease body stability when the left and right wings encounter different flow conditions. Wing splinting also led to a small increase in body rotation rates in turbulent airflow, but this change was not statistically significant, possibly because bees with stiffened wings changed their flight behavior in turbulent flow. Overall, we find that wing flexibility improves flight stability in bumblebees, adding to the growing appreciation that wing flexibility is not merely an inevitable liability in flapping flight, but can enhance flight performance.