Visual deprivation and distance estimation in the praying mantis larva

Abstract. Young larvae of the praying mantis, Tenodera sinensis Saussure, were placed on an off-centre island surrounded by a round arena with six black bars painted on a white inner wall. In this situation, it was shown that the horizontal peering movements of the head often seen in mantids are in fact used to measure distances; motion parallax may be involved in this process. Aimed jumps that followed peering were taken to be the distinct result of an absolute distance measurement. Specific visual deprivation such as painting over of certain parts of the eye with opaque black varnish or degeneration of the fovea with sulforhodamine showed that: absolute evaluation of distance is only possible with two fully intact eyes; the peering mechanism is under visual control; and visual experience has a long-term effect on distance measurement involving peering movements.     

Motion parallax as a source of distance information in locusts and mantids

This review article is devoted to results on distance measurement in locusts (e.g., Wallace, 1959; Collett, 1978; Sobel, 1990) and mantids. Before locusts or mantids jump toward a stationary object, they perform characteristic pendulum movements with the head or body, called peering movements, in the direction of the object. The fact that the animals over- or underestimate the distance to the object when the object is moved with or against the peering movement, and so perform jumps that are too long or short, would seem to indicate that motion parallax is used in this distance measurement. The behavior of the peering parameters with different object distances also indicates that not only retinal image motion but also the animal’s own movement is used in calculating the distance.     

The role of edges in the selection of a jump target in Mantis religiosa

Before jumping to a landing object, praying mantids determine the distance, using information obtained from retinal image motion resulting from horizontal peering movements. The present study investigates the peering-jump behaviour of Mantis religiosa larvae with regard to jump targets differing in shape and size. The experimental animals were presented with square, triangular and round target objects with visual extensions of 20 degrees and 40 degrees. The cardboard objects, presented against a uniform white background, were solid black or shaded with a gradation from white to black. It was found that larger objects were preferred to smaller ones as jump targets, and that the square and triangle were preferred to the round disk. When two objects were presented, no preference was exhibited between square and triangular objects. However, when three objects were presented, the square was preferred. For targets with a visual angle of 40 degrees, the amplitude and velocity of the horizontal peering movements were greater for the round disk than for the square or triangle. This amplification of the peering movements suggests that weaker motion signals are generated in the case of curved edges. This may help to account for the preference for the square and triangle as jump targets.     

Similarities and differences in the peering-jump behavior of three grasshopper species (Orthoptera: Caelifera)

The peering-jump behavior was studied for the common field grasshopper Chorthippus brunneus , the meadow grasshopper C. parallelus and the alpine grasshopper Miramella alpina (Orthoptera, Caelifera). It was found that immediately before jumping M. alpina executes primarily unilateral object-related peering movements, with approximately twice the amplitude and velocity of the predominantly bilateral object-related peering movements of the other two species. Whereas M. alpina almost always jumped toward the black stripes in the experimental arena, the other species jumped toward both the black stripes and the white spaces between them. All three species preferred the same pattern of black stripes, which permitted them to view one black stripe frontally, with an additional black stripe to the left and right, in the lateral visual field. The similarities and differences in the peering-jump behavior of the three grasshopper species is discussed with regard to visual perception (parallax cues) and environmental adaptation.     

Spatial vision in binocular and monocular common field grasshoppers (Chorthippus brunneus)

Abstract The ability of the common field grasshopper Chorthippus brunneus to discriminate between different distances under binocular and monocular stimulus conditions is investigated based upon the peering‐jump behaviour. The results show that information obtained from only one eye is sufficient for the grasshopper to determine the jump direction and distance. However, information obtained from both eyes is advantageous for relative distance determination. It is hypothesized that the motion parallax signals from the left and right eye may be summed, thus improving performance. There is no behavioural evidence of a more complex correlation of the information from the two eyes.     

Community effects of praying mantids: a meta-analysis of the influences of species identity and experimental design

Abstract 1. Generalist arthropod predators are ubiquitous in terrestrial ecosystems but experimental studies have yielded little agreement as to their effects on prey assemblages. Drawing on results from a suite of experimental field studies, a meta‐analysis was conducted of the impact of praying mantids (Mantodea: Mantidae) on arthropod assemblages in order to identify predictable and unpredictable effects of these extremely generalised predators. 2. Results across different experiments were synthesised using the log response ratio framework, with a focus on quantifying net mantid impacts on arthropod density across taxonomic orders and trophic levels of arthropods, paying special attention to the contribution of mantid species identity and experimental design variables, such as the use of cages, length of experiment, and manipulated mantid density. 3. Calculated on a per mantid‐day basis, the net impacts of Tenodera sinensis on arthropod density were generally weaker but more predictable than the effects of Mantis religiosa. Mantids in general had weak negative effects on density for most taxa but exhibited strong negative and positive effects on some taxa. Tenodera sinensis tended to have negative effects on Homoptera, Diptera, and Hemiptera and herbivores as a group, however M. religiosa exhibited greater variation in response of different taxa that appeared to be affected more strongly by experimental design. The effects of Stagmomantis carolina tended to be negative or non‐significant. 4. Experimental cages had little influence on either the sign or magnitude of net community impacts for T. sinensis, however cage experiments reversed the sign of the mean effect for two of six taxonomic orders when the experimental predator was M. religiosa. Cages also increased the variability of effect size greatly for M. religiosa but not for T. sinensis. 5. It was concluded that it is possible to use log response ratios to determine general, predictable trends in a well‐studied system. Similar meta‐analyses of generalist predator effects in other systems should produce predictions of how these predators influence food webs, an important step towards defining more clearly the influences of generalist predators on community structure and dynamics.     

Responses to worm-like-wriggling models by the praying mantis: effects of amount of motion on prey recognition

Adult females of the mantis, Tenodera angustipennis, were presented with a wriggling model, consisting of six circular spots positioned in a row horizontally and adjacently. During presentation, this model wriggled like a worm by moving some spots. When the motion of the model was small (the number of moving spots ≤2), the mantis sometimes stalked the model with peering movements but seldom struck it. When the motion was large (the number of moving spots ≥3), the mantis frequently fixated, rapidly approached, and struck the model. These results suggest that the mantis changes its approach behavior depending on the amount of prey motion. Disappearance of some terminal spots at the stationary end hardly affected the rates of fixation, peering, and strike. The model that wriggled at each end elicited lower rates of fixation and strike than the model that wriggled at one end. These results suggest that the mantis responds to only the fastest moving part of the wriggling model when the motion of the model is large. Electronic Publication     

Visual gaze control during peering flight manoeuvres in honeybees

As animals travel through the environment, powerful reflexes help stabilize their gaze by actively maintaining head and eyes in a level orientation. Gaze stabilization reduces motion blur and prevents image rotations. It also assists in depth perception based on translational optic flow. Here we describe side-to-side flight manoeuvres in honeybees and investigate how the bees’ gaze is stabilized against rotations during these movements. We used high-speed video equipment to record flight paths and head movements in honeybees visiting a feeder. We show that during their approach, bees generate lateral movements with a median amplitude of about 20 mm. These movements occur with a frequency of up to 7 Hz and are generated by periodic roll movements of the thorax with amplitudes of up to ±60°. During such thorax roll oscillations, the head is held close to horizontal, thereby minimizing rotational optic flow. By having bees fly through an oscillating, patterned drum, we show that head stabilization is based mainly on visual motion cues. Bees exposed to a continuously rotating drum, however, hold their head fixed at an oblique angle. This result shows that although gaze stabilization is driven by visual motion cues, it is limited by other mechanisms, such as the dorsal light response or gravity reception.     

How Far Stationary Contrast Boundaries Can Be Away to Elicit Behavioral Responses in Praying Mantis

The aim of the present study was to investigate the distance at which vertical black and white stripes (contrast boundaries) elicit object-related behavioral responses in 6th instar and adults of the praying mantis Mantis religiosa. The mantids reacted when the contrast boundaries were not further away than 60 cm. However, with increasing distance (>20 cm), the contrast boundaries became progressively less significant for the mantids. Jumps/preparation of jumps could be observed between 10 and 30 cm. The results are supportive for distance measurement of up to 20–30 cm, which corresponds to distance accessible for the insect. It seems that image motion cues induced by peering movements play an important role.     

Effect of axis alignment on in vivo shoulder kinematics

Background. To describe 3D shoulder joint movements, the International Society of Biomechanics (ISB) recommends using segment coordinate systems (SCSs) on the humerus, scapula and thorax, and joint coordinate systems (JCSs) on the shoulder. However, one of the remaining problems is how to define the zero angles when the arm is in an initial reference position. The aim of this paper is to compare various methods of determining the JCSs of the shoulder that make it possible to define the zero angles of the arm in the resting position.

Methods. Able-bodied subjects performed elevation movements in the scapular plane, specifically neutral, internal and external rotations of the humerus. The initial humerus position (at the beginning of the arm movement) and range of motion were analysed for the purpose of clinical interpretation of arm attitude and movement. The following four different JCSs were explored: (1) the standard JCS, defined as recommended by the ISB, (2) a first aligned JCS, where the humerus SCS is initially aligned with the scapula SCS, (3) a second aligned JCS, where the opposite operation is performed and 4) a third aligned JCS, where both the humerus and the scapular SCS are initially aligned with the thorax SCS.

Findings. The second aligned JCS was the only method that did not produce any exaggerated range of movement in either anatomical plane.

Interpretation. Mathematical JCS alignment allows clearer clinical interpretation of arm attitude and movement.     

On the barn owl’s visual pre-attack behavior: I. Structure of head movements and motion patterns

Barn owls exhibit a rich repertoire of head movements before taking off for prey capture. These movements occur mainly at light levels that allow for the visual detection of prey. To investigate these movements and their functional relevance, we filmed the pre-attack behavior of barn owls. Off-line image analysis enabled reconstruction of all six degrees of freedom of head movements. Three categories of head movements were observed: fixations, head translations and head rotations. The observed rotations contained a translational component. Head rotations did not follow Listing’s law, but could be well described by a second-order surface, which indicated that they are in close agreement with Donder’s law. Head translations did not contain any significant rotational components. Translations were further segmented into straight-line and curved paths. Translations along an axis perpendicular to the line of sight were similar to peering movements observed in other animals. We suggest that these basic motion elements (fixations, head rotations, translations along a straight line, and translation along a curved trajectory) may be combined to form longer and more complex behavior. We speculate that these head movements mainly underlie estimation of distance during prey capture.     

A comparison of ten digestive enzymes reveals a lack of chitinase in a phasmid and the loss of two β-glucanases in a mantid

In all developmental stages, the phasmid Peruphasma schultei (Conle & Hennemann, 2005) is an obligate herbivore, whereas the mantid Hierodula membranacea (Burmeister, 1838) is an obligatory carnivore. In P. schultei, the luminal activity of all enzymes is approxximately 50% in the crop and 50% in the midgut, which corresponds to the approximate 50 : 50 ratio of volumes of these two regions. These ratios would be expected in insects with a constant feeding rate on an unvaried diet. The enzyme activity and volume ratios in Hierodula membranacea vary considerably because of the irregular feeding habits. These differences in activity ratios between phasmids and mantids are not associated with the obligate phytophagous or carnivorous diet. The ratio of membrane bound to luminal aminopeptidases and disaccharidases in the midgut of both species are not significantly different and are within the normal range of other paurometabolous insects. Cellobiase and other plant cell wall digesting enzymes, laminarinase and cellobiase, are present in the phasmid but totally lacking in the mantid. The obligate carnivorous feeding habits of mantids could represent a selective factor leading to the loss of the ability to produce β-glucanases. Chitinase is a moulting enzyme in all insects, whereas, in H. membranacea, chitinase also occurs as a luminal digestive enzyme. This modified enzyme function requires production and secretion in another tissue, namely the midgut.     

Visually targeted reaching in horse-head grasshoppers

Visually targeted reaching to a specific object is a demanding neuronal task requiring the translation of the location of the object from a two-dimensionsal set of retinotopic coordinates to a motor pattern that guides a limb to that point in three-dimensional space. This sensorimotor transformation has been intensively studied in mammals, but was not previously thought to occur in animals with smaller nervous systems such as insects. We studied horse-head grasshoppers (Orthoptera: Proscopididae) crossing gaps and found that visual inputs are sufficient for them to target their forelimbs to a foothold on the opposite side of the gap. High-speed video analysis showed that these reaches were targeted accurately and directly to footholds at different locations within the visual field through changes in forelimb trajectory and body position, and did not involve stereotyped searching movements. The proscopids estimated distant locations using peering to generate motion parallax, a monocular distance cue, but appeared to use binocular visual cues to estimate the distance of nearby footholds. Following occlusion of regions of binocular overlap, the proscopids resorted to peering to target reaches even to nearby locations. Monocular cues were sufficient for accurate targeting of the ipsilateral but not the contralateral forelimb. Thus, proscopids are capable not only of the sensorimotor transformations necessary for visually targeted reaching with their forelimbs but also of flexibly using different visual cues to target reaches.     

Effects of luminance, size, and angular velocity on the recognition of nonlocomotive prey models by the praying mantis

Adult females of the mantis Tenodera angustipennis were presented with the "nonlocomotive" prey model, a static rectangle with two lines oscillating regularly at its sides, generated on a computer display. The models were varied in rectangle luminance (black, gray, and light gray), rectangle height (0.72, 3.6, and 18 mm), rectangle width (0.72, 3.6, and 18 mm), and angular velocity of oscillating lines (65°, 260°, and 1040°/s) to examine their effects on prey recognition. Before striking the model, the mantis sometimes showed peering movements that involved swaying its body from side to side. The black model of medium size (both height and width) elicited higher rates of fixation, peering, and strike responses than the large, small, or gray model. The model of medium angular velocity elicited a higher strike rate than that of large or small angular velocity, but angular velocity had little effect on fixation and peering. We conclude that mantises respond to a rectangle in deciding whether to fixate, and to both rectangle and lines in deciding whether to strike after fixation. Received: September 2, 1999 / Accepted: March 21, 2000     

Wing kinematics during natural leaping in the mantids Mantis religiosa and Iris oratoria

High-speed flash photography was used to analyse wing movements of Mantis religiosa and Iris oratoria at the moment of take-off during natural leaping. Wing kinematics are compared with those of the similarly designed locust wing. Iris oratoria showed strong coupling between leg extensor and wing depressor muscle activity immediately prior to take-off, with a possible enhancement of jump momentum. A 'clap and peel' was observed in the hind wings of both species during the first downstroke. Supination in the mantid forewing is accomplished by a backward rotation of the whole of the main wing plate about the claval furrow. Both fore- and hind wings show pronounced ventral flexure at the lower point of stroke reversal. Camber was developed in the hind wing during the upstroke as well as the downstroke. Possible roles of the claval furrow and transverse flexion in protecting the forewing base against torsional forces generated at stroke reversal are discussed.     

Visual position stabilization in the hummingbird hawk moth, Macroglossum stellatarum L. I. Behavioural analysis

Optomotor responses of freely flying hawk moths, Macroglossum stellatarum, were characterized while the animals were hovering in front of and feeding on a dummy flower. Compensatory translational and rotational movements of the hawk moth were elicited by vertical grating patterns moving horizontally, mimicking imposed rotational and translational displacements of the animal in the horizontal plane. Oscillatory translational and rotational pattern motion leads to compensatory responses that peak in the frequency range between 2 Hz and 4 Hz. The control systems mediating the translational and rotational components of the optomotor response do not seem to influence each other. The system mediating translational responses is more sensitive in the fronto-lateral part of the visual field than in the lateral part; the opposite is true for the rotational system. The sensitivity of the translational system does not change along the vertical, whereas the rotational system is much more sensitive to motion in the dorsal than in the ventral part of the visual field. These sensitivity gradients may reflect an adaptation to the specific requirements of position stabilization in front of flowers during feeding. Accepted: 13 August 1997     

Identification of the molecular origin and development of a panzootic caused by Beauveria bassiana in praying mantis populations in eastern China

A panzootic in praying mantid species Tenodera sinensis and Statilia maculate, caused by Beauveria bassiana, occurred in north, southwest and southeast regions of Anhui Province, eastern China in Autumn, 2009. A 3-d principal component analysis (PCA) of 123 isolates from three sites revealed that the B. bassiana populations were heterogeneous with obvious dominance. Furthermore, the causal source of the panzootic in Anhui was shown to be polyphyletic. The populations were homogenized into homogenous subunits for investigation of genetic structure by inter-simple sequence repeat (ISSR) markers. Variance was greater than 70%, largely due to genetic differences within populations and subpopulations. Genetic distances and genetic differentiation were negatively associated with geographic distances and it was speculated that this was due to the effects of monsoons and topography. Mantid isolates were divided into five pathotypes based on a two-way cluster analysis of genetic distance. Pathotype I consisted of the predominant subpopulations of Huangcangyu and Chashui populations, with a genetic distance of 0.120 and gene flow up to 1.833. This pathotype caused a widespread epizootic in north and southwest Anhui, and Pathotype III caused enzootic at Site A in September and then epizootic in October, while the other three pathotypes caused enzootics at all three investigation sites. The widespread epizootics and isolated enzootics composed the polyphyletic panzootic in Anhui. A strong gene flow between isolates from the two mantid species was identified, resulting in negligible gene differentiation. This indicated a lack of host specificity in mantid isolates of B. bassiana.     

Visual determinants of escape in tiger beetle larvae (Cicindelidae)

Larvae of tiger beetles (Coleoptera: Cicindelidae) are burrow-dwelling, visual ambush predators which withdraw into their burrows with the passing of large objects. Laboratory experiments confirmed that stimulation of each of the four principal stemmata can elicit escape and that the necessary visual stimulus is contracting, expanding, or transverse movement of a high-contrast image. Response frequency increases as a power function of contrast. Whole-field dimming is ineffective. Movement of large images composed of multiple texture elements, e.g., checkerboards, does not elicit escape, even if each element is much larger than the system's minimum visible angle (4–8° depending upon image contrast). In pilot experiments with a single figure before a textured background, coherent movement of the two inhibits escape, whereas motion in opposite directions does not. Thus, the processing mechanism functions as a feature detector and directs a response to large, single, moving objects.     

Behavioural-analytical studies of the role of head movements in depth perception in insects,birds and mammals

In this review, studies of the role of head movements in generating motion parallax which is used in depth perception are examined. The methods used and definitiveness of the results vary with the animal groups studied. In the case of insects, studies which quantify motor outputs have provided clear evidence that motion parallax evoked by head movements is used for distance estimation and depth perception. In the case of birds and rodents, training studies and analyses of the head movements themselves have provided similar indications. In the case of larger mammals, due to a lack of systematic experiments, the evidence is less conclusive.