Tetragonisca guard bees interpret expanding and contracting patterns as unintended displacement in space

Spatial Vision and Visually Guided Behavior in Apidae

The family Apidae, which is amongst the largest bee families, are important pollinators globally and have been well studied for their visual adaptations and visually guided behaviors. This review is a synthesis of what is known about their eyes and visual capabilities. There are many species-specific differences, however, the relationship between body size, eye size, resolution, and sensitivity shows common patterns. Salient differences between castes and sexes are evident in important visually guided behaviors such as nest defense and mate search. We highlight that Apis mellifera and Bombus terrestris are popular bee models employed in the majority of studies that have contributed immensely to our understanding vision in bees. However, other species, specifically the tropical and many non-social Apidae, merit further investigation for a better understanding of the influence of ecological conditions on the evolution of bee vision.

Visual Sensory Signals Dominate Tactile Cues during Docked Feeding in Hummingbirds

Animals living in and interacting with natural environments must monitor and respond to changing conditions and unpredictable situations. Using information from multiple sensory systems allows them to modify their behavior in response to their dynamic environment but also creates the challenge of integrating different, and potentially contradictory, sources of information for behavior control. Understanding how multiple information streams are integrated to produce flexible and reliable behavior is key to understanding how behavior is controlled in natural settings. Natural settings are rarely still, which challenges animals that require precise body position control, like hummingbirds, which hover while feeding from flowers. Tactile feedback, available only once the hummingbird is docked at the flower, could provide additional information to help maintain its position at the flower. To investigate the role of tactile information for hovering control during feeding, we first asked whether hummingbirds physically interact with a feeder once docked. We quantified physical interactions between docked hummingbirds and a feeder placed in front of a stationary background pattern. Force sensors on the feeder measured a complex time course of loading that reflects the wingbeat frequency and bill movement of feeding hummingbirds, and suggests that they sometimes push against the feeder with their bill. Next, we asked whether the measured tactile interactions were used by feeding hummingbirds to maintain position relative to the feeder. We created two experimental scenarios-one in which the feeder was stationary and the visual background moved and the other where the feeder moved laterally in front of a white background. When the visual background pattern moved, docked hummingbirds pushed significantly harder in the direction of horizontal visual motion. When the feeder moved, and the background was stationary, hummingbirds generated aerodynamic force in the opposite direction of the feeder motion. These results suggest that docked hummingbirds are using visual information about the environment to maintain body position and orientation, and not actively tracking the motion of the feeder. The absence of flower tracking behavior in hummingbirds contrasts with the behavior of hawkmoths, and provides evidence that they rely primarily on the visual background rather than flower-based cues while feeding.

Hummingbirds control hovering flight by stabilizing visual motion

Relatively little is known about how sensory information is used for controlling flight in birds. A powerful method is to immerse an animal in a dynamic virtual reality environment to examine behavioral responses. Here, we investigated the role of vision during free-flight hovering in hummingbirds to determine how optic flow--image movement across the retina--is used to control body position. We filmed hummingbirds hovering in front of a projection screen with the prediction that projecting moving patterns would disrupt hovering stability but stationary patterns would allow the hummingbird to stabilize position. When hovering in the presence of moving gratings and spirals, hummingbirds lost positional stability and responded to the specific orientation of the moving visual stimulus. There was no loss of stability with stationary versions of the same stimulus patterns. When exposed to a single stimulus many times or to a weakened stimulus that combined a moving spiral with a stationary checkerboard, the response to looming motion declined. However, even minimal visual motion was sufficient to cause a loss of positional stability despite prominent stationary features. Collectively, these experiments demonstrate that hummingbirds control hovering position by stabilizing motions in their visual field. The high sensitivity and persistence of this disruptive response is surprising, given that the hummingbird brain is highly specialized for sensory processing and spatial mapping, providing other potential mechanisms for controlling position.

A stingless bee can use visual odometry to estimate both height and distance

Bees move and forage within three dimensions and rely heavily on vision for navigation. The use of vision-based odometry has been studied extensively in horizontal distance measurement, but not vertical distance measurement. The honey bee Apis mellifera and the stingless bee Melipona seminigra measure distance visually using optic flow–movement of images as they pass across the retina. The honey bees gauge height using image motion in the ventral visual field. The stingless bees forage at different tropical forest canopy levels, ranging up to 40 m at our site. Thus, estimating height would be advantageous. We provide the first evidence that the stingless bee Melipona panamica utilizes optic flow information to gauge not only distance traveled but also height above ground, by processing information primarily from the lateral visual field. After training bees to forage at a set height in a vertical tunnel lined with black and white stripes, we observed foragers that explored a new tunnel with no feeder. In a new tunnel, bees searched at the same height they were trained to. In a narrower tunnel, bees experienced more image motion and significantly lowered their search height. In a wider tunnel, bees experienced less image motion and searched at significantly greater heights. In a tunnel without optic cues, bees were disoriented and searched at random heights. A horizontal tunnel testing these variables similarly affected foraging, but bees exhibited less precision (greater variance in search positions). Accurately gauging flight height above ground may be crucial for this species and others that compete for resources located at heights ranging from ground level to the high tropical forest canopies.

Defensive behavior of honey bees: organization, genetics, and comparisons with other bees

One key advantage of eusociality is shared defense of the nest, brood, and stored food; nest defense plays an important role in the biology of eusocial bees. Recent studies on honey bees, Apis mellifera, have focused on the placement of defensive activity in the overall scheme of division of labor, showing that guard bees play a unique and important role in colony defense. Alarm pheromones function in integrating defensive responses; honey bee alarm pheromone is an excellent example of a multicomponent pheromonal blend. The genetic regulation of defensive behavior is now better understood from the mapping of quantitative trait loci (QTLs) associated with variation in defensiveness. Colony defense in other eusocial bees is less well understood, but enough information is available to provide interesting comparisons between A. mellifera and other species of Apis, as well as with allodapine, halictine, bombine, and meliponine bees. These comparative studies illustrate the wide variety of evolutionary solutions to problems in colony defense in the Apoidea.