Structure of the coxa and homeosis of legs in Nematocera (Insecta: Diptera)

Construction of the middle and hind coxae was investigated in 95 species of 30 nematoceran families. As a rule, the middle coxa contains a separate coxite, the mediocoxite, articulated to the sternal process. In most families, this coxite is movably articulated to the eucoxite and to the distocoxite area; the coxa is radially split twice. Some groups are characterized by a single split. The coxa in flies is restricted in its rotation owing to a partial junction either between the meron and the pleurite or between the eucoxite and the meropleurite. Hence the coxa is fastened to the thorax not only by two pivots (to the pleural ridge and the sternal process), but at the junction named above. Rotation is impossible without deformations; the role of hinges between coxites is to absorb deformations. This adaptive principle is confirmed by physical modelling. Middle coxae of limoniid tribes Eriopterini and Molophilini are compact, constructed by the template of hind coxae. On the contrary, hind coxae in all families of Mycetophiloidea and in Psychodidae s.l. are constructed like middle ones, with the separate mediocoxite, centrally suspended at the sternal process. These cases are considered as homeotic mutations, substituting one structure with a no less efficient one.     

Common motor mechanisms support body load in serially homologous legs of cockroaches in posture and walking

We studied the mechanisms underlying support of body load in posture and walking in serially homologous legs of cockroaches. Activities of the trochanteral extensor muscle in the front or middle legs were recorded neurographically while animals were videotaped. Body load was increased via magnets attached to the thorax and varied through a coil below the substrate. In posture, tonic firing of the slow trochanteral extensor motoneuron (Ds) in each leg was strongly modulated by changing body load. Rapid load increases produced decreases in body height and sharp increments in extensor firing. The peak of extensor activity more closely approximated the maximum velocity of body displacement than the body position. In walking, extensor bursts in front and middle legs were initiated during swing and continued into the stance phase. Moderate tonic increases in body load elicited similar, specific, phase dependent changes in both legs: extensor firing was not altered in swing but was higher after foot placement in stance. These motor adjustments to load are not anticipatory but apparently depend upon sensory feedback. These data are consistent with previous findings in the hind legs and support the idea that body load is countered by common motor mechanisms in serially homologous legs.     

Biomechanics of the multisclerite middle coxa in flies (Diptera)

The middle coxa in Calliphora consists of three sclerites. Two rear sclerites are able to rotate relative to the front sclerite about the intracoxal axis (ICA). The turn ahead about ICA puts the leg in a peculiar position with minimal aerodynamic resistance. Sclerites are articulated in a form of complex kinematic chain. Distances between articulations were measured; using them, various configurations of the model coxa were obtained by geometrical synthesis, the turn about ICA was simulated, and the muscle driving the turn ahead was revealed (the hind elevator). The middle leg with the complex coxa in most of Brachycera is specialised for the advanced flight performance.     

Gimbals in the insect leg

We studied the common kinematic features of the coxa and trochanter in cursorial and raptorial legs, which are the short size of the podomers, predominantly monoaxial joints, and the approximate orthogonality of adjacent joint axes. The chain coxa-trochanter with its short elements and serial orthogonality of joint axes resembles the gimbals which combine versatility and tolerance to external perturbations. The geometry of legs was studied in 23 insect species of 12 orders. Insects with monoaxial joints were selected. The joint between the trochanter and the femur (TFJ) is defined either by two vestigial condyles or by a straight anterior hinge. Direction of the joint axes in the two basal podomers was assessed by 3D measurements or by goniometry in two planes. Length of the coxa is <15% (mostly <8%) of the total length of the cursorial leg, that of the trochanter <10%. Angles between the proximal and distal joint axes in the middle coxa range from 124 to 84 degrees (mean 97+/-14 degrees ), in the trochanter (in all legs studied) from 125 to 72 degrees (mean 90+/-13 degrees ). Vectors of the distal axis in the coxa are concentrated about the normal to the plane defined by the proximal axis and the midpoint between the distal condyles. These vectors in the trochanter lie at various angles to the normal; angles are correlated with the direction of the TFJ relative to the femur. Range of reduction about the TFJ is over 60 degrees in the foreleg of Ranatra linearis, Mantispa lobata and the hind leg in Carabus coriaceus (confirming observations of previous authors), 40-60 degrees in the foreleg of Vespa crabro and in the middle one in Ammophila campestris, 10-30 degrees in other studied specimens. The special role of the trochanter in autotomy and in active propulsion in some insect groups is discussed. The majority of insects possess small trochanters and slightly movable TFJs with the joint axis laying in the femur-tibia plane. We pose the hypothesis that the TFJ damps external forces, the vectors of which lie off the femur-tibia plane, the reductor muscle acting as a spring. Thus the TFJ contributes to dynamic stability of legged locomotion.     

Influence of a movable support under one leg on human vertical posture during standing with asymmetrical load on legs

Changes in the vertical posture maintenance were studied when the legs were placed on supports of different degrees of mobility and part of the body weight was voluntarily transferred to one leg. The aim of these experiments was to explore how the mobility of support under the feet affects the balance and how this effect depends on the load distribution between the legs during standing. When both legs were on rigid immovable supports, the vertical posture was maintained by control of the center of pressure (CP) on both legs. When the subject transferred the weight to one foot, the posture was maintained mainly due to the control of CP of the loaded leg. When the legs were on supports of different degrees of mobility, the balance was maintained by the leg on the immovable support. This result was observed both when the subject stood with symmetrical load on the legs and when the load was transferred to one leg. Even when the leg was unloaded but placed on the immovable support, its CP moved more compared to the CP of the loaded leg on a movable support. The results obtained show that the support mobility is a factor that determines the mechanisms of posture maintenance, and this factor is more significant than load distribution between the legs. Thus, the upright posture is maintained with the physical properties of support under the feet taken into account.     

The jumping mechanism of cicada Cercopis vulnerata (Auchenorrhyncha, Cercopidae): skeleton-muscle organisation, frictional surfaces, and inverse-kinematic model of leg movements

In Auchenorrhyncha, jumping is achieved by metathoracic muscles which are inserted into the trochanter of the hind leg. The synchronisation of movements of the hind legs is a difficult problem, as the leg extension that produces the jump occurs in less than 1 ms. Even slight asynchrony could potentially result in failure of a jump. Both the synchronisation of the movements of a pair of jumping legs, and their stabilisation during a jump, seem to be important problems for small jumping insects. The present study was performed in order to clarify some questions of the functional morphology of the leafhopper jumping mechanism. It is based on skeleton-muscle reconstruction, high-speed video recordings, transmission (TEM) and scanning electron microscopic (SEM) investigations of the cuticle, together with 3D inverse-kinematic modelling of angles and working zones of hind leg joints of cicada Cercopis vulnerata (Cercopidae). The complete extension of the hind leg takes less than 1 ms, which suggests that the jump is powered not only by the muscle system, but also by an elastic spring. Histological staining and fluorescence microscopy showed resilin-bearing structures, responsible for elastic energy storage, in the pleural area of the metathorax. Synchronisation of hind leg movements may be aided by microtrichia fields that are located on the medial surface of each hind coxa. In Auchenorrhyncha, hind coxae are rounded in their anterior and lateral parts, whereas medial parts are planar, and contact each other over a rather large area. The inverse-kinematic model of propulsive leg movements was used to draw the surface outlined by the medial surface of the coxa, during the jump movement. This is a cone surface, faced with its bulged-in side, medially. Surfaces outlined by the movements of both right and left coxae overlap in their anterior and posterior positions. In both extreme positions, coxae are presumably connected to each other by coupled microtrichia fields. Thus, in extreme positions, both coxae can be moved synchronously.     

Intersegmental transfer of sensory signals in the stick insect leg muscle control system

Intersegmental coordination during locomotion in legged animals arises from mechanical couplings and the exchange of neuronal information between legs. Here, the information flow from a single leg sense organ of the stick insect Cuniculina impigra onto motoneurons and interneurons of other legs was investigated. The femoral chordotonal organ (fCO) of the right middle leg, which measures posture and movement of the femur-tibia joint, was stimulated, and the responses of the tibial motoneuron pools of the other legs were recorded. In resting animals, fCO signals did not affect motoneuronal activity in neighboring legs. When the locomotor system was activated and antagonistic motoneurons were bursting in alternation, fCO stimuli facilitated transitions from flexor to extensor activity and vice versa in the contralateral leg. Following pharmacological treatment with picrotoxin, a blocker of GABA-ergic inhibition, the tibial motoneurons of all legs showed specific responses to signals from the middle leg fCO. For the contralateral middle leg we show that fCO signals encoding velocity and position of the tibia were processed by those identified local premotor nonspiking interneurons known to contribute to posture and movement control during standing and voluntary leg movements. Interneurons received both excitatory and inhibitory inputs, so that the response of some interneurons supported the motoneuronal output, while others opposed it. Our results demonstrate that sensory information from the fCO specifically affects the motoneuronal activity of other legs and that the layer of premotor nonspiking interneurons is a site of interaction between local proprioceptive sensory signals and proprioceptive signals from other legs.     

Motor output to the protractor and retractor coxae muscles in stick insects walking on a treadwheel

ABSTRACT. The motor output to the protractor and retractor mucles moving the coxa of the middle leg of Carausius morosus was recorded from the thoracic nerves during walking on a treadwheel. The leg movements on the wheel were generally similar to those found in free-walking animals, but tripod coordination was relatively independent of period, and the coordination of the adult animal on the wheel was most closely related to that found in free-walking first instars. The activity of a common inhibitor and four excitatory axons of the retractor and an excitatory axon of the protractor were followed for 850 steps (in six animals) to give a summary of the behaviour of the different units. The motor activity is less stereotyped than that previously reported for insects. There was strong reciprocity between the antagonists, but this was not directly correlated with the forward and backward movements of the legs. The first part of the stance phase of the leg was accompanied by a strong burst in the protractor nerve and relatively little retractor activity. This was followed by the main retractor burst which occupied the last 60% of the stance phase. The results are compared with motor output records of the locust and with earlier force-plate measurements on the stick insect. It must be concluded that the mesothoracic leg initially resists forward movement of the body by the other legs during a typical walking step.     

A dynamic model of thoracic differentiation for the control of turning in the stick insect

Leg movements of stick insects (Carausius morosus) making turns towards visual targets are examined in detail, and a dynamic model of this behaviour is proposed. Initial results suggest that front legs shape most of the body trajectory, while the middle and hind legs just follow external forces (Rosano H, Webb B, in The control of turning in real and simulated stick insects, vol. 4095, pp 145–156, 2006). However, some limitations of this explanation and dissimilarities in the turning behaviour of the insect and the model were found. A second set of behavioural experiments was made by blocking front tarsi to further investigate the active role of the other legs for the control of turning. The results indicate that it is necessary to have different roles for each pair of legs to replicate insect behaviour. We demonstrate that the rear legs actively rotate the body while the middle legs move sideways tangentially to the hind inner leg. Furthermore, we show that on average the middle inner and hind outer leg contribute to turning while the middle outer leg and hind inner leg oppose body rotation. These behavioural results are incorporated into a 3D dynamic robot simulation. We show that the simulation can now replicate more precisely the turns made by the stick insect. This work was supported by CONACYT México and the European Commission under project FP6-2003-IST2-004690 SPARK.     

Cyclorrhaphous Dipterans (Diptera Cyclorrhapha) inhabiting bird nests in Russia and Ukraine

A synopsis of 20 species of Diptera Cyclorrhapha from 10 families occurring in bird nests is presented. Some species were found for the first time in bird nests. The roles of each fly species in the bird nest consortia, the mode of larval life, associations with nestlings or nest substrate are discussed. Most flies are widely distributed, the possible explanations for which are proposed.     

Tight turns in stick insects

We investigated insects Carausius morosus walking whilst hanging upside down along a narrow 3 mm horizontal beam. At the end of the beam, the animal takes a 180° turn. This is a difficult situation because substrate area is small and moves relative to the body during the turn. We investigated how leg movements are organised during this turn. A non-contact of either front leg appears to indicate the end of the beam. However, a turn can only begin if the hind legs stand in an appropriate position relative to each other; the outer hind leg must not be placed posterior to the inner hind leg. When starting the turn, both front legs are lifted and usually held in a relatively stable position and then the inner middle leg performs a swing-and-search movement: The leg begins a swing, which is continued by a searching movement to the side and to the rear, and eventually grasps the beam. At the same time the body is turned usually being supported by the outer middle leg and both hind legs. Then front legs followed by the outer middle leg reach the beam. A scheme describing the turns based on a few simple behavioural elements is proposed.     

佩妃延腹榕小蜂的产卵行为

榕树与传粉榕小蜂之间的互惠共生关系是协同进化研究领域中的热点之一。榕树除了与传粉榕小蜂共生外,它还为许多非传粉榕小蜂提供食物和生境。佩妃延腹榕小蜂Philotrypesis pilosa Mayr腹部第8～9节背板极度延伸,形似长长的产卵鞘,其后更长的才是真正的产卵鞘。它将产卵针刺入榕果的果壁,产卵于果内。该蜂是对叶榕Ficus hispida L. 的传粉榕小蜂Ceratosolen solmsi （Mayr）的盗食性寄生蜂。我们利用数码照相机记录了佩妃延腹榕小蜂产卵的全过程,详细描述了其产卵行为。发现了前人没有发现的下列行为特点： (1）当雌蜂找到合适的产卵位点时,身体呈倒立状,后足扶持产卵鞘到选定的产卵位点;2）从开始插入产卵针到产卵鞘向后弹出,腹部第8～9节背板延伸部分与产卵鞘之间有两次大幅度的靠拢与分开,第一次靠拢与分开是保证产卵针以最佳的垂直角度插入果内,第二次是使产卵鞘向后弹出,将暴露在外的产卵针顺利地插入果内;3）雌蜂产卵针沿榕果直径方向（最短距离）插入果壁;4）前足与后足比中足发达,与整个产卵过程中支撑身体的行为有关 。     

Experimental Studies and Dynamics Modeling Analysis of the Swimming and Diving of Whirligig Beetles (Coleoptera: Gyrinidae)

Whirligig beetles (Coleoptera, Gyrinidae) can fly through the air, swiftly swim on the surface of water, and quickly dive across the air-water interface. The propulsive efficiency of the species is believed to be one of the highest measured for a thrust generating apparatus within the animal kingdom. The goals of this research were to understand the distinctive biological mechanisms that allow the beetles to swim and dive, while searching for potential bio-inspired robotics applications. Through static and dynamic measurements obtained using a combination of microscopy and high-speed imaging, parameters associated with the morphology and beating kinematics of the whirligig beetle''s legs in swimming and diving were obtained. Using data obtained from these experiments, dynamics models of both swimming and diving were developed. Through analysis of simulations conducted using these models it was possible to determine several key principles associated with the swimming and diving processes. First, we determined that curved swimming trajectories were more energy efficient than linear trajectories, which explains why they are more often observed in nature. Second, we concluded that the hind legs were able to propel the beetle farther than the middle legs, and also that the hind legs were able to generate a larger angular velocity than the middle legs. However, analysis of circular swimming trajectories showed that the middle legs were important in maintaining stable trajectories, and thus were necessary for steering. Finally, we discovered that in order for the beetle to transition from swimming to diving, the legs must change the plane in which they beat, which provides the force required to alter the tilt angle of the body necessary to break the surface tension of water. We have further examined how the principles learned from this study may be applied to the design of bio-inspired swimming/diving robots.     

Ants swimming in pitcher plants: kinematics of aquatic and terrestrial locomotion in Camponotus schmitzi

Camponotus schmitzi ants live in symbiosis with the Bornean pitcher plant Nepenthes bicalcarata. Unique among ants, the workers regularly dive and swim in the pitcher's digestive fluid to forage for food. High-speed motion analysis revealed that C.?schmitzi ants swim at the surface with all legs submerged, with an alternating tripod pattern. Compared to running, swimming involves lower stepping frequencies and larger phase delays within the legs of each tripod. Swimming ants move front and middle legs faster and keep them more extended during the power stroke than during the return stroke. Thrust estimates calculated from three-dimensional leg kinematics using a blade-element approach confirmed that forward propulsion is mainly achieved by the front and middle legs. The hind legs move much less, suggesting that they mainly serve for steering. Experiments with tethered C.?schmitzi ants showed that characteristic swimming movements can be triggered by submersion in water. This reaction was absent in another Camponotus species investigated. Our study demonstrates how insects can use the same locomotory system and similar gait patterns for moving on land and in water. We discuss insect adaptations for aquatic/amphibious lifestyles and the special adaptations of C.?schmitzi to living on an insect-trapping pitcher plant.     

Morphometric and morphological variation between two different populations of Phlebotomus major s.l. from endemic and non‐endemic foci of visceral leishmaniasis in Iran

Populations of Phlebotomus major were examined in two endemic and nonendemic foci of visceral leishmaniasis in Iran. Based on the shape of the aedeagus and ventrally located hairs of coxite and pharyngeal armatures, two morphotypes were found sympatrically in the endemic area of Borazjan. Significant differences in morphometric survey were observed in at least 11 measured characters. The aedeagus of the non‐endemic Miyandoab morphotype, and also of a few specimens from Borazjan, is completely parallel throughout its length with a slightly expanded end. Ventrally located hairs of the middle coxite were longer and more compact. It is close morphologically to P. major neglectus (P. neglectus), which was recently recorded from Iran. It is also morphologically similar to P. notus, which has not yet been reported from Iran and needs further investigation. The aedeagus of the morphotype occurring only in Borazjan is narrower in the middle and the hairs are closer to the base of the coxite and are shorter and more outspread, which makes it similar to P. major krimensis or P. neglectus. The two morphotypes occurring sympatrically in Borazjan do not appear to be subspecies and it may be premature to propose them as separate species. Further investigation is needed to clarify the actual status of P. major s. l. in Iran.     

复齿叶蜂属分类研究(膜翅目,蕨叶蜂科)

记述了中国新纪录属复齿叶蜂属2种,包括1新种黑股复齿叶蜂Iconia nigrofemoratga sp.nov.和中国1新纪录种白股复齿叶蜂I.versicolor Malaise 1944.该属仅分布于亚洲东南部,已知仅模式种1种.新种与模式种的主要区别是后足基节和股节黑色,触角基部3节和腹部第3、第6～7背板黑色无白斑,中胸前侧片刻点间具粗糙刻纹.编制了分种检索表,绘制了形态特征图.新种模式标本分别保存于中南林学院昆虫标本室和中国科学院上海昆虫研究所.     

A cockroach that jumps

We report on a newly discovered cockroach (Saltoblattella montistabularis) from South Africa, which jumps and therefore differs from all other extant cockroaches that have a scuttling locomotion. In its natural shrubland habitat, jumping and hopping accounted for 71 per cent of locomotory activity. Jumps are powered by rapid and synchronous extension of the hind legs that are twice the length of the other legs and make up 10 per cent of the body weight. In high-speed images of the best jumps the body was accelerated in 10 ms to a take-off velocity of 2.1 m s(-1) so that the cockroach experienced the equivalent of 23 times gravity while leaping a forward distance of 48 times its body length. Such jumps required 38 μJ of energy, a power output of 3.4 mW and exerted a ground reaction force through both hind legs of 4 mN. The large hind legs have grooved femora into which the tibiae engage fully in advance of a jump, and have resilin, an elastic protein, at the femoro-tibial joint. The extensor tibiae muscles contracted for 224 ms before the hind legs moved, indicating that energy must be stored and then released suddenly in a catapult action to propel a jump. Overall, the jumping mechanisms and anatomical features show remarkable convergence with those of grasshoppers with whom they share their habitat and which they rival in jumping performance.     

Processing of tactile information in neuronal networks controlling leg movements of the Locust

The successful, coordinated, posture and locomotion of any animal requires a precise and continuous adjustment of limb movements by sensory feedback from extero- and proprioceptors associated with the legs. We here review the recent advances in our understanding of how specific local adjustments of the hind legs of the desert locust, Schistocerca gregaria, are made in response to tactile signals from two different classes of exteroceptor on a leg. The aim is to understand particular features of the organization of neuronal networks and how different types of constituent interneurones contribute to the processing of sensory signals. This information can then be used to define the design principles that govern the organization of sensory-motor networks.     

The First Mitochondrial Genome of the Sepsid Fly Nemopoda mamaevi Ozerov, 1997 (Diptera: Sciomyzoidea: Sepsidae), with Mitochondrial Genome Phylogeny of Cyclorrhapha

Sepsid flies (Diptera: Sepsidae) are important model insects for sexual selection research. In order to develop mitochondrial (mt) genome data for this significant group, we sequenced the first complete mt genome of the sepsid fly Nemopoda mamaevi Ozerov, 1997. The circular 15,878 bp mt genome is typical of Diptera, containing all 37 genes usually present in bilaterian animals. We discovered inaccurate annotations of fly mt genomes previously deposited on GenBank and thus re-annotated all published mt genomes of Cyclorrhapha. These re-annotations were based on comparative analysis of homologous genes, and provide a statistical analysis of start and stop codon positions. We further detected two 18 bp of conserved intergenic sequences from tRNA^Glu-tRNA^Phe and ND1-tRNA^Ser(UCN) across Cyclorrhapha, which are the mtTERM binding site motifs. Additionally, we compared automated annotation software MITOS with hand annotation method. Phylogenetic trees based on the mt genome data from Cyclorrhapha were inferred by Maximum-likelihood and Bayesian methods, strongly supported a close relationship between Sepsidae and the Tephritoidea.