In his introduction to this detailed survey of knowledge of insect societies, the author points out that research on insect sociology has proceeded in three phases, the natural history phase, the physiological phase and the population-biology phase. Advances in the first two phases have permitted embarkation in the third phase on a more rigorous theory of social evolution based on population genetics and writing this book, the author wished to relate the three phases of research on insects and to express insect sociology as population biology. A glossary of terms, a considerable bibliography and a general index are included. Other CABI sites 

The Insect Societies

http://link.springer.com/content/pdf/10.1007/978-3-642-67868-4_4.pdf

Spatial Vision in Arthropods

Underwater imaging is important for scientific research and technology as well as for popular activities, yet it is plagued by poor visibility conditions. In this paper, we present a computer vision approach that removes degradation effects in underwater vision. We analyze the physical effects of visibility degradation. It is shown that the main degradation effects can be associated with partial polarization of light. Then, an algorithm is presented, which inverts the image formation process for recovering good visibility in images of scenes. The algorithm is based on a couple of images taken through a polarizer at different orientations. As a by-product, a distance map of the scene is also derived. In addition, this paper analyzes the noise sensitivity of the recovery. We successfully demonstrated our approach in experiments conducted in the sea. Great improvements of scene contrast and color correction were obtained, nearly doubling the underwater visibility range.

/pdf/recovery-of-underwater-visibility-and-structure-by-246zw4v3ed.pdf

Recovery of underwater visibility and structure by polarization analysis

To control force accurately under a wide range of behavioral conditions, the central nervous system would either require a detailed, continuously updated representation of the state of each muscle (and the load against which each is acting) or else force feedback with sufficient gain to cope with variations in the properties of the muscles and loads. The evidence for force feedback with adequate gain or for an appropriate central representation is not sufficient to conclude that force is the major controlled variable in normal limb movements.Morton's hypothesis, that length is controlled by a follow-up servo, has a number of difficulties related to the delays, gains, variability, and specificity in feedback pathways comprising potential servo loops. However, experimental evidence is consistent with these pathways providing servo assistance for some movements produced by coactivation of α- and static γ-motoneurons. Dynamic γ-motoneurons may provide an additional input for adaptive control of different types of movements.The idea that feedback is used to compensate for changes in muscle stiffness has received experimental support under static postural conditions. However, reflexes tend to increase rather than decrease the range of variation in muscle stiffness during some cyclic movements. Theoretical problems associated with the regulation of stiffness are also discussed. The possibilities of separate control systems for velocity or viscosity are considered, but the evidence is either negative or lacking. I conclude that different physical variables can be controlled depending on the type of limb movement required. The concept of stiffness regulation is also useful under some conditions, but should probably be extended to the regulation of the visco-elastic properties (i.e., the mechanical impedance) of a muscle or joint.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0140525X00013327

What muscle variable(s) does the nervous system control in limb movements

Polarized Light in Animal Vision

The stick insect Carausius morosus maintains the distance between the substrate and its body. The underlying feed-back servo mechanism has been analyzed in intact animals under open loop conditions by changing the body-substrate distance in a sinusoidal fashion. The center position z c has been varied as parameter and the force the animal elicits along its high axis has been measured. The response amplitude A is a nonlinear function of z c. This nonlinear relationship between A and z c is most probably caused by the relationship between the torque excerted at the joints and the measured force. The responses to sinusoidal stimulation reveal band-pass character of the feed-back loop. Due to the nonlinearity of the system the average value of the response to sinusoidal disturbances depends upon the frequency of modulation. The change of the average value with the frequency of modulation is partially due to cocontraction of the extensor and flexor muscles.

Regulation of the body-substrat-distance in the stick insect: Responses to sinusoidal stimulation

The visual fixation response of the mealworm beetle Tenebrio molitor, elicited by black stripes upon a bright background is studied in an arena and by means of the Y-maze technique. In the arena the distribution n(β) of the beetle's angular position β is measured at different distances from the centre, which is also the starting point. If the black stripe is narrow, the maximum of n(β) coincides with the centre of the stripe ("centre-fixation" Figure 1a). If one half of the panorama is black, the distribution n(β) has two maxima, which are near the borders between the black and white regions ("edge-fixation" Figure 1b). In the Y-maze experiments the beetle is tethered, but its head is free to move. The black stripes elicit turning tendencies F(β), the strength of which depends upon the angular distance β between the centre of the stripe and the animal's body axis. If the black stripe is narrow, the stable zero crossing of F(β) lies at β=0, in agreement with the centre fixation in the arena (Fig. 3). If the stripe is 180° wide, two stable zero crossings are obtained near the border lines between the black and white regions, provided that the panorama is rotated around the animal with an angular velocity w larger than about 0.08°/s (Fig. 4). Below this value of w only one stable zero crossing at β=0 exists (Fig. 6). Thus the tethered beetle's response underlies a transition between centre resp. edge fixation at a critical angular velocity of the drum. Some implications of this surprising phenomenon with respect to the mechanism of fixation and negative phototaxis are discussed but at present it is considered primarily a challenge for further investigation.

Visual edge fixation and negative phototaxis in the mealworm beetle Tenebrio molitor

Two alternative circuits to realize the reafference principle are considered and quantitatively analyzed. Both are combinations of a conventional control loop with negative feedback and linear transfer functions, as well as of an efference copy branch. The feedback control loop compensates for passive movements of the body or of its parts, and generates active movements, whenever the set point differs from zero. The efference copy branch should eliminate sensory messages to higher brain centres during active body movements and, thus, mediate perceptual stability. In one of the combinations, discussed also briefly by Mittelstaedt (1971), the efference copy branch interacts with and thus modifies the properties of the feedback loop. The performance of this circuit is very sensitive to variations of the system parameters and, therefore, requires precise adjustment. When the transfer function of the efference copy branch exactly matches that of the feedback loop and its gain amounts to 1, this circuit performs as a control loop with an integrator in the negative feedback branch: there is no steady state control error. However, for certain parameter combination the circuit becomes unstable. In the alternative circuit proposed here, the efference copy branch does not interfere with the feedback loop. It is robust against parameter variations. The transient properties of both circuits are described under simplified assumptions regarding the linear transfer functions in the different branches.

A note on the reafference principle

The feed back mechanism subserving the regulation of the body-substrate-distance in the stick insect Carausius morosus has been investigated by means of step-like stimuli. Based on the results obtained in open-loop experiments a model is developed which describes the results obtained under closed loop conditions. When the experimental animal is pushed or pulled in dorso-ventral direction an initial fast and a subsequent very slow change of the body height z over the substrate are observed. The late slow response is a nearly linear function of time and can last for more than one hour if the animal is pulled with moderate forces. It withstands less effectively if pushed. During the slow phase of the response sudden changes of z and of the slope of the z(t)-curves occur, presumably due to corresponding changes of the amplification within the feed back loop.

Dezső Varjú

Papers

Polarized Light in Animal Vision

Regulation of the body-substrat-distance in the stick insect: Responses to sinusoidal stimulation

Visual edge fixation and negative phototaxis in the mealworm beetle Tenebrio molitor

A note on the reafference principle

Regulation of the body-substrate-distance in the stick insect: Step responses and modelling the control system