Thermovoltaic properties of hornet silk.

In silk from the larval silk caps of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae), temperature-dependent changes in the electric voltage have been recorded, with rise in the voltage occurring mainly upon rise in the temperature between 10-36 degrees C. The peak voltage was measured between 32-38 degrees C and attained 240-360 mV, but with further increase in temperature, the voltage decreased, dropping to 0 mV at about 45-50 degrees C. Upon second measurement (of same silk specimen), the voltage peak usually occurred later (by 8-9 degrees C) and at higher temperature than in the first measurement. Continuous measurements during warming up to 30 degrees C followed by cooling down to 15 degrees C yielded an hysteresis between the warming "line" and the cooling "line", the former often straight and the latter usually curved. Maintaining the silk specimen at a fixed temperature for a prolonged period (hours) initially causes the voltage to rise, then remain steady, and finally drop. Boiling the silk caps in tap water for 7-10 min exerts some changes in the silk properties, mainly a decrease in voltage level. The general behavior of the silk suggests that it is a polymer endowed with the qualities of an organic semiconductor. The various properties of the larval silk are discussed in great detail.

Perovskites in the comb roof base of hornets: their possible function.

On the ceiling of the Oriental hornet comb cell, there are mineral granules of polycrystalline material known to belong to the group of perovskites. In a comb cell intended to house a worker hornet, the roof base usually carries one or several such perovskite granules containing titanium (Ti), whereas in the roof base of a cell housing a developing queen, there are usually several granules containing a high percentage of silicon (Si), aluminum (Al), calcium (Ca), and iron (Fe), but very little if any Ti. In worker comb cells, Ti usually appears as ilmenite (FeTiO3). Besides documenting the above-mentioned facts, this report discusses possible reasons for the appearance of ilmenite crystals in worker cells only and not in queen cells.

Magnetic minerals. Keystone-like crystals in cells of hornet combs.

The hexagonal brood-rearing cells inside the nest combs of the hornet Vespa orientalis are uniform in both their architecture and orientation. We have discovered that each cell contains a minute crystal that projects down from the centre of its domed roof and has a composition typical of the magnetic mineral ilmenite. These tiny crystals form a network that may act like a surveyor's spirit-level, helping the hornets to assess the symmetry and balance of the cells and the direction of gravity while they are building the comb.

Learning and navigation of hornets: role of the various light perceiving organs.

The present study reports on experiments carried out on workers of Vespa orientalis (Hymenoptera, Vespinae). The experiments involved: learning of the workers upon their breeding box, evaluation of their ability to navigate back to the breeding box from ever increasing distances, and the effect which masking the various light perceiving organs has on the homing flight of hornets. The test hornets were removed from their breeding box to which they became accustomed and then released at gradually increasing distances from it (100 to 1000 meters) so as to assess their ability to return home. The group of hornets returning from a given distance was on the next day released at a greater distance, and so forth, and their homing capability was then compared between regular control groups and hornets that were coated with masking paint in various light-perceiving regions such as the clypeus, frons, ocelli and ommatidia on the head or segments 3 or 4 of the gaster, the whole gaster or various combinations of the two (head and gaster). It was found that in all the groups combined (test + various controls) only about 44% of hornets released at a distance of 100 meters from the breeding box, found their way home. The percentage of homing hornets diminished with increasing distance from home and generally they responded in accordance with the formula: S(d)=exp(dp/beta), where d=distance; S(d)=the proportion of hornets expected to return from d; P=the shape parameter of the distribution: beta=the 'scale' parameter of the distribution. Percentage of successfully homing hornets was significantly larger in control hornets than in treated ones only at a release distance of 1000 meters.

Navigation and thermophotovoltaic activity by hornets at different light conditions: the influence of UVB blockers.

The aim of the present investigation was two-fold: a) to observe the homing of the Oriental hornet, Vespa orientalis (Hymenoptera, Vespinae) from different distances; and b) to study the photothermoelectric activity of hornet cuticle obtained from the subjects of goal (a) and kept frozen for a number of days prior to its testing. In both the above mentioned phases of the investigation, an attempt was made to assess how the covering of the hornets' cuticle with Ultra Violet B (UVB) blockers affects their activity as compared to the control. Flying hornets were observed to return to the nest from distances of up to 7 km, once they had learned the way back. However, covering of the cuticle with UVB blockers increases the percentage of 'non-returners' to nearly 100%. Covering the cuticle completely or partly with a number of UVB blockers (except for Sisley) proves lethal for the hornets within 24 hours. A statistical model on homing is proposed of the effect of range, of covering with UVB blockers and covering ocelli with Tippex. In the wing of the hornet there is increase in the electric current with rise in the temperature and decrease in the current upon drop of the temperature, but light has no effect on this alar (wing) current. Contrariwise, the body cuticle of the hornet responds to both temperature and illumination in terms of its electric current. Coating of the cuticle with UVB blockers causes in the wing (under all conditions of illumination) and in the cuticle (only in the dark) a moderation in the amplitude of the photothermoelectric current.

Thermal properties of hornet colonies: thermography of individual hornets and their nests and the role of the pupal silk in thermoregulation.

The present study focused on temperature assessments within a hornet nest. The measurements encompassed adult hornets, brood combs and the various stages of brood, and involved a thermographic method. Body parts of adult hornets were found to vary in their temperature, with the thorax eliciting the highest temperature and the abdomen the lowest. Similarly, there were thermal variances between larvae at instars 4-5, light-colored pupae and dark pupae. The measurements were made at day and night (when the entire population was present in the nest) on nests containing thousands of individuals at various ages. Most of the pupae measured during October were hornet drones. The usual air temperature between the (subterranean) combs was 28.7 degrees C, while the outside (ground level) temperature was 23.5 degrees C. The paper discusses the creation of heat by hornets, the thermoregulation throughout night and day, both by the hornets proper as well as by their products (comb and silk). Also discussed is the intra-nest conversion of one form of energy to another, as heat to electric current or vice versa.

Hypothesis on radar sensing and communication by hornets: comments on their antennal organulles and electrical activity.

Our study shows that the antenna of the hornet is densely covered from base to tip with six types of organulles, namely, a trichoid organulle, about 23 microm in length, a campaniform organulle which is 12 microm long, a heretofore undescribed structure measuring about 9 microm in length which we have now named the Agmon organulle, a rather flattened placoid organulle measuring about 25 microm in length and not projecting on the antennal surface, and finally rounded structures about 3 microm in diameter which are indented in the cuticle and resemble extraretinal photoreceptors. All the above-mentioned structures occur in the workers and drones, and the latter also possess an additional structure, namely, the tyloid which is about 254 microm long. Such organulles as protrude from the antennal surface are mostly orientated distally and their length is about half that of similar organulles on the hornets body. Yet their density on the antenna is greater than elsewhere on the body and in fact on all the antennal segments (12 in the workers and 13 in the drones) the entire surface area seems to be occupied by them. The most numerous are the trichoids, while the other organulles mentioned are fewer in number. In measuring the electric properties of the antennae, we obtained the following values: 10-80 nanoAmpers (nA), 60-100 milliVolt (mV) and several scores of Mega Ohms (Momega) in the dark, as compared to 10-20 nA, 150-200 mV and few Momega under illumination. We found that in many respects, the cuticle in the antenna behaves like an organic semiconductor possessing thermophotovoltaic (TPV) properties. Apart from contemplating that the role of the antennal organulles is as a mechanoreceptor, a chemoreceptor or a combination of the two, we also raise the conjecture that these organulles might serve as elements that pick up and broadcast at submillimetric wavelengths, and that the electric energy extant in the vespan antennae supplies the energy source for this kind of activity.

Silk produced by hornets: thermophotovoltaic properties-a review.

This article deals with the silk weave produced by pupating larvae of the Oriental hornet and its electric properties. Larvae of this hornet commence pupation at approximately 2 weeks of age. Creation of the cocoonal silk weave requires a number of hours and the encased pupa remains in the cocoon for approximately 2 more weeks before ecloding as an adult. The silk weave is initially of a creamish white color, but gradually becomes brown-gray owing to the activity of certain bacteria secreted in the silk. The silk weave is composed of fibers arranged in multiple layers with interposed surfaces occupying a considerable part of the area and containing pockets of bacteria. The spun silk contains both metallic and non-metallic elements, mostly K and Cl but also Mg, P, S, Ca, Ti and V. Shaped as a dome, the silk projects considerably beyond the cell proper, contributing importantly to its total volume and providing a shield for the contained pupa against predators, parasites, or extreme changes in temperature, as well as affording a 'sterile and clean room' in which the pupa can form its new cuticle without the interference of contaminating dust particles or the turbulence of air currents. The silk is endowed with electric properties. Inter alia, a thermoelectric phenomenon was observed in the dark, namely, upon increase in temperature the current rose to several hundred nano Amperes (nA); in light, a photovoltaic effect was observed involving voltages of several dozen millivolts (mV), with a sharp transition between the current and voltage during transition from darkness to light. Also recorded was a very high electric capacitance, amounting to scores of milli farads (mF). In all, the pupal silk behaves like an organic semiconductor, in that its electric properties are temperature-dependent, and it also displays ferroelectric properties. Additionally, a luminescence phenomenon was recorded on the silk, wherein excitation at wavelengths within the UV(i.e. 249, 290 and 312 nm) range yielded an emission spectrum at a wavelength of 450 and of 530 nm. The silk caps are anisotropic in that the emission from the outside is lower than that from the inside. By way of recap, the various mentioned properties of the pupal silk are discussed from their biological and physical aspects.

Thermophotovoltaic (TPV) properties of hornet cuticle as dependent on relative humidity.

This paper deals with the thermophotovoltaic (TPV) properties of the cuticle of the Oriental hornet as assessed over time under different regimens of relative humidity (RH). The tests were run at two levels of RH, namely, 30% vs. 90%. Each experiment entailed measuring the cuticular voltage and current in the dark as compared to under illumination (white light = 700 Lux), and at a temperature range of 20-30 degrees C. It was found that increase in the RH level boosts the current values by 2-3 orders of magnitude; contrariwise, the voltage values rise by about three times with drop in the RH. At high RH, the changes in current become rhythmical and each cycle of warming-cooling assumes a distinctly cyclic pattern. Under illumination, the current decreases, the polarity reverses and the resistance increases. The obtained results are describable by a model of electric conductance upon a surface, in this case the hornet cuticle; the findings are also discussed and compared with similar phenomena recorded from other substances possessing the properties of organic semiconductors.

Grid formation in hornet cuticle induced by silk spun during pupation.

Examinations carried out via atomic force microscope (AFM) on the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae) revealed, on the cuticle of the gaster in the region of the yellow stripes, flats bearing a grid in the form of parallel strips. Such configurations, of the same dimensions, were obtained also by superposition imaging of the longitudinal fibrils in the pupal silk weave, which are comprised of a central fibril of fibroin and an outer coating of sericin. In the latter instance, the configurations were revealed in regions where the outer coating of the fibers was disrupted or occurred only intermittently. We conjecture that the silk fibers and flats which encase the 5th-instar larva as it pupates in the dark somehow exert an effect on the morphology of the epicuticle in the metamorphosing pupa and that the effect is achieved via irradiation of heat waves, by an electric charge, or by the induction of a magnetic field. We discuss the possible implications of the presence of grids on the cuticles of adult hornets and also their possible connection with solar cells and light polarization.

The solar cell in hornet cuticle: nanometer to micrometer scale.

This paper focuses on structures observed by scanning and transmission electron microscopy and atomic force microscopy upon and within the abdominal cuticle of the Oriental hornet, Vespa orientalis. Taken together, these structures form an 'organ' whose function is the absorption ef sunlight and storage of the resultant electrical energy. In principle, this organ resembles a solar cell. The gaster of the hornet is cone-shaped and comprised of the following components: (i) structures protruding from the epicuticular surface, which are arranged lengthwise and generally parallel to one another like furrows; (ii) these furrows overlie straight, terrace-like flat surfaces, which are shaped like imperfect polygons, each about 100 microm2 in area; (iii) each terrace abuts an area that is positioned lower than it, the juncture between the two is comprised of a stripe, which is vertical to the topmost polygonal flat and perpendicular to the furrows; (iv) between the juncture stripes, at distances of 10-100 microm apart, there are smooth flat surfaces reminiscent of a parabolic mirror of about 20 microm2, each possessing a rounded, eccentric area recessed to a depth of about 7.5 microm (i.e. a heat sinking housing), underneath which can be seen the upper part of the peripheral photoreceptor (PP); (v) cuticular lamellae, about 30 in number, create a pore between them in the PP region, fold in vertical fashion and enwrap the entire PP down to its broad base which is immersed in a yellow bacterial layer and where the cuticular layers are very thin. Presumably the light energy impinges vertically upon the individual terraced flat surfaces while the hornet is in flight, creating such situations for a fraction of a second at a time. The insolation is absorbed more intensively in the furrows, owing to their shape. The picked up solar energy is now transmitted as electric charges from the furrows to the conduction stripes between abutting terraces, and thence to: (a) the rhodopsin pigment in the PP (the smaller moiety), or (b) the numerous cuticular layers, depending on the energy level of the picked up photons (the larger moiety), and (c) finally to the bacterial layer for storage in its walls. The latter region will be a p-type as compared to the energy stored in the layers of brown cuticle. The cuticle thus was found to contain many PPs but within the cuticle they are dispersed in contrast to the situation in the compound eye, where the many photoreceptors are concentrated.

Purification, characterization and anticoagulant activity of a proteolytic enzyme from Vespa orientalis venom.

The anticoagulant effect of Vespa orientalis venom sac extract (VSE) was attributed to a proteolytic process, involving mainly coagulation factors VIII and IX [Joshua, H., Ishay, J., 1975. Toxicon 13, 11-20; Korenberg et al., 1988. Toxicon 26, 1169-1176]. Preliminary purification of the proteolytic activity showed the presence of three separate proteases. One of which, protease I, was purified. The purified enzyme migrated as a double band on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). The molecular weights of the bands, under reduced conditions were 42 and 44 kD. Both bands retained activity after the electrophoretic run. The enzyme hydrolyses bovine factor IX (BFIX), factor X (BFX) and prothrombin. The pH optimum for the degradation of BFIX was 7.0 and its isoelectric point is above pH 10. The amino acid composition of the protease was determined.

In most poorly controlled glyburide-treated type 2 diabetic patients drug withdrawal causes further increase in glycemia not accompanied by changes in insulin secretion.

To find out whether the secondary failure of glyburide in type 2 diabetes is complete or partial, we studied 38 patients, age (M +/- SD) 69 +/- 9 years, suffering from diabetes from 13.5 +/- 8.4 years and treated with glyburide for 5-13 years, with poor glycemic control (glycohemoglobin 10.6 +/- 2.6%). Serum glucose, insulin and C-peptide were assayed before and 1 h and 2 h after a simulated meal load (355 Cal), after which the drug was replaced with placebo for 4 weeks, and the test repeated. After glyburide withdrawal, fasting glycemia increased from 10.3 +/- 3.3 to 15.1 +/- 4.4 mmol/L (p < 0.001), but in 3/38 patients, it even decreased and in five others the changes were less than +/- 2 mmol/L. These changes negatively but only weakly correlated with initial glycemia: r = 0.4123, p < 0.010. The mean post-meal glycemia at 1 h and 2 h increased respectively by 3.3 and 5.9 mmol/L (both p < 0.001). Neither the levels of glycemia nor its changes after the glyburide withdrawal correlated with the levels of, or changes in, insulin or C-peptide. We conclude that in most but not all type-2 diabetic patients, poorly controlled with glyburide, the drug still retains some limited therapeutic effectiveness, and therefore its withdrawal causes further deterioration of control with the almost equal increases in fasting and post-meal levels of glycemia. These changes are not accompanied by decrease in insulin secretion.

Acceleration and modulation of facial nerve regeneration by exposure to a moderate hypergravitic field.

Quantitative histological study revealed that regeneration of sectioned guinea pig facial nerve is accelerated by exposure to a moderate hypergravitic field of 1.6g. A two fold increase in rate of regeneration and in sprouting was observed. Scar tissue formation was significantly reduced in animals exposed to the hypergravitic field. The results confirm a previous study in which regeneration was evaluated clinically and by qualitative histology.

The white blood cell line: changes induced in mice by hypergravity.

The effect of hypergravity on the white blood cell (WBC) line of mice was investigated by use of horizontal centrifuge. Several sets of experiments were performed, in which the parameters measured were the WBC and differential cell count in the peripheral blood. In another experiment, lymphocyte counts from the spleen, lymph nodes, and the thymus were measured. The needed samples were taken from the mice during a stay of 7-40 days under a hypergravity of 1.6G. The test groups that were placed on the arms of the centrifuge (1.6G) were compared with stationary control groups (1G) and a rotating control group located at the center of the centrifuge (1G). Such a comparison revealed the test animals to be deficient on all counts, to wit, showing a decrease in total number of WBC's, a decrease in lymphocyte number in the peripheral blood and a decrease in the number of lymphocyte in the spleen and thymus. The decrease of lymphocytes in peripheral blood was characterized by two different slopes--an early and temporary decrease at the first days of the experiment evident in both test and rotating control groups followed by a temporary increase, and a later persistent decrease, evident only in the test group, while in the rotating control lymphocyte counts reverted to normal. There were no significant differences in monocyte or neutrophil counts, except for a temporary increase in the number of neutrophils which peaked on the seventh day. In order to evaluate the effect of hypergravity on restoration of hematopoiesis following hematopoietic suppression, 5-fluoro-uracil (5-FU) was administered i.v. to both the experimental and control mice. Suppression of bone marrow was observed in all groups injected with 5-FU, but while there was later an increase in cell counts in the control groups, there was no such increase in the test group subjected to hypergravity.

Micromorphology of the dorsal ocelli of the Oriental hornet.

The development of vision in animals throughout evolution has been reviewed by Sir Stewart Duke-Elder, whose survey of the sense of sight ranges from lowly Crustaceans to mammals and man. According to Duke-Elder each ocellus is formed by the "fusion of two or more ocelli, each with its own retina and pigment cup". This process of 'ocellation' probably occurred independently in a number of phyla. So far as Hymenoptera are concerned, at least in Bombus, only the median ocellus has retained any evidence of its 'dual' origin. In hornets, there are three ocelli which are organized on the dorsal part of the head and receive their innervation from the optical lobes that are located in the protocerebrum. Proceeding from the exterior to the interior, the ocelli are generally composed of a cornea, followed by corneogenic cell layers and then by a layer of sensory cells from which emerges the ocellar nerve. Thus, in wasps and hornets the ocelli consist of a group of visual cells beneath a common lens and they possibly accentuate the response to light stimuli that are perceived by the compound eyes. Recently, the ocelli have been ascribed roles in orientation and navigation. In honeybees the sensitivity of the ocelli to light at various wavelengths was compared with that of the compound eyes, and was found to be different, to wit: in the ocellus there were two peaks--one of UV light at a wavelength of 335-340 nm and the other of green light at 490 nm, whereas in compound eye the peaks were at 350 nm and 540 nm. From all the foregoing, it would seem that the role of the ocelli in insects in general and in hornets in particular is not yet sufficiently clear. The present study was undertaken to elucidate the structure of the ocelli in the Oriental hornet and possibly also their function.

Are ciliary hair cells and photoreceptors components of a gravitic system of the hornet Vespa orientalis?

Social wasps, including the sub-family Vespinae, are social insects that build combs beneath the ground which are directed towards the gravitic pull of the earth, and this in dim light or complete darkness. On the inner side of the frons plate in social wasps there is a gravity sensing apparatus composed of static and dynamic nerve fibers, some of which connect between the frons plate and the brain. It is highly probable that the interaction between the fibers and the various structures in the head is responsible for the proprioceptive ability of hornets, including gravity detection. Ishay et al called the apparatus involved, the "Ishay Organ", and also reported the presence of (stereo) cilia on the inner side of the frons plate. The frons plate which bears the gravity organs functions as a photovoltaic system. Additionally there are throughout the cuticle, at intervals of several micrometers apart, distinct pores which are the outlets of peripheral photoreceptors. In the past various investigators have studied the ciliar structures of different insects mainly by TEM, but we have now studied the hair cells in hornets by FE-SEM, to obtain a complete 3-dimensional image of the various hair cell structures involved.

Regeneration of guinea pig facial nerve: the effect of hypergravity.

Exposure to moderate hypergravity improves the regenerative capacity of sectioned guinea-pig facial nerve. The improvement in regeneration is tri-directional as follows: a) an average 1.7 fold increase in rate of regeneration in guinea pigs subjected to hypergravity; b) a 25% enhancement of facial muscle activity following the exposure to hypergravity; and c) improvement in the quality of regeneration from an esthetic standpoint. A good correlation was recorded between the histological structure of the severed nerve at the end of the regeneration and the clinical results.

Thermo- and photoelectric current in hornet cuticle.

Thermoelectric and photoelectric currents were measured in the cuticle of hornets. The spontaneous current in the studied specimens ranged between 30-40 nAmp under conditions of darkness whereas under illumination the current drops to near zero. Upon warming up to 28-29 degrees C, the current rises to 50-200 nAmp but subsequently, after a while, it declines, regardless of whether the temperature is held steady, continues to rise or is lowered. In light, the current values are lower than in darkness and this under all conditions. When the specimen is charged with an electric current under fixed temperature, the current attains several microAmp in darkness but is usually less than that under illumination by about one order of magnitude. The capacitance values range between 1-7 mFarad both in light and in the dark. Possible mechanisms for creating this cuticular current and the changes which it undergoes under the various experimental conditions are discussed, and so also the properties of hornet cuticle as a semiconductor and possible applications of the described phenomena in everyday life of hornets.

Light curtails sleep in anesthetized hornets: extraretinal light perception.

In the present study effects of light on the sleep duration of anesthetized hornets (Vespa orientalis) were investigated. Following initial anesthesia by diethyl ether the sleeping time of workers and drones at 22 degrees C in the dark was 59 +/- 15 min. After repeated anesthesia the sleeping time was 30 +/- 15 min in the dark. When exposed to polychromatic light from a halogen lamp of 230 mW/cm2, focused on a spot of the cuticle of the hornet, the sleeping time was markedly shortened so that following initial as well as repeated anesthesia the hornets woke up after 4.5 +/- 2.9 min. Any decrease in light intensity resulted in an increase in the sleeping time but irradiances of less than 14 mW/cm2 had no measurable influence on the wake-up time. After illumination with polychromatic light from a mercury lamp the sleeping times were much shorter than after illumination with a halogen lamp at the same conditions and intensity. This difference is attributed to the relatively higher portion of U.V. light in the total emission of the Hg lamp. Effects of the spectral composition of the incident light beam on the wake-up of the sleeping hornets were also investigated. Near U.V. light in the 300-400 nm region was found to be most efficient. Shorter wavelengths as well as wavelengths between 400-470 nm had less influence and wavelengths above 470 nm had very little effect on the wake up. The sleeping times of hibernating queens were relatively longer than those of workers and drones under the same conditions. These effects are ascribed to the extraretinal light perception. The possible reasons underlying this phenomenon are discussed.