Temperature dependence of the electrical resistivity of social wasp cuticle: A comparative study

Resistance to electricity by social wasp cuticle is temperature dependent within the range of 1–40°C. This was measured on the species Vespa orientalis (the Oriental hornet), Vespa crabro (the European hornet) and the wasp Dolichovespula saxonica. The resistance at first decreases with increased temperature, reaching a nadir which differs according to species, and then rises again up to 40°C, the highest temperature tested. It is suggested that the cuticular changes in resistivity at different temperatures reflect the wasp's mechanism for detecting and regulating the temperature in their normal environment.     

Thermoelectric (seebeck) effect of the cuticle of social wasps

The thermoelectric (Seebeck) coefficient ($\text{S =}\text{ΔV}\text{ΔT}$) in various cuticular areas of the Oriental hornet (Vespa orientalis) fluctuates from 0·3 to 2·4 mV deg^?1 within a temperature range of 27–36°C and when the temperature difference between the two measuring electrodes (ΔT) is 0·6–8·0°C. The values measured on the brown-colored cuticle suggest an n-type conduction, while those measured on the yellow-colored cuticle point to a p-type conduction. It is suggested hornets use this phenomenon for temperature detection.     

Both olfactory and visual cues promote the hornet Vespa velutina to locate its honeybee prey Apis cerana

Predators use olfactory, visual and sometimes acoustic cues from the preys to assess food information. However, it is not known if the aggressive hornets (Vespa spp.) use olfactory, visual, or both types of information to find and recognize prey. In the present study, we trained hornet workers (Vespa velutina) to a feeding area. Once the hornets began consistently foraging at this feeding area, we determined whether they located prey (bees, Apis cerana) via olfactory or visual cues. We did this by testing whether hornets were attracted to a dummy bait (bee dummy bait or non-bee dummy bait) treated with extracts of honeybee cuticular hydrocarbons. We then tested whether hornets could distinguish between bee dummy bait and cotton ball dummy bait, both treated with bee odors. Hornets preferred the dummy treated with bee odors, and bee dummies (with bee images) were more attractive to the hornet than the cotton ball dummies with only bee odors. These results clearly indicate that a combination of olfactory and visual cues helps the hornet to locate its prey.     

Temperature dependence of the electrical resistance of hornet cuticle: A statistical model

The electric resistance to d.c. of the yellow strips in the cuticle of worker hornets was measured in the dark under temperature changes within the optimal range of activity outside the nest (10–32°C). A distinct inverse correlation was observed between the resistance and the temperature, the former decreasing with rise of the latter. In all, each individual hornet measured was subjected to four successive cycles of measurement during which the specimens underwent warming followed by cooling. A slight unidirectional rise in the resistance both during warming and cooling was observed between two successive cycles. A typical thermal hysteresis loop formed between the warming and cooling lines, thus suggesting a memory effect.     

The association between changes in the intravaginal electrical resistance and the in vitro measurements of vaginal mucus electrical resistivity in cattle

A system was developed for measuring in vitro the electrical resistivity (ρ) of vaginal mucus samples collected throughout a complete oestrous cycle from three Hereford × Friesian cows. Measurements of intravaginal electrical resistance (Rv) and mucus electrical resistivity were made in six Hereford × Friesian cows throughout a complete normal oestrous cycle. Both Rν and ρ fluctuated during dioestrus and fell to a minimum value at oestrus. The decrease in ρ was larger than that of Rν. A significant correlation was found between Rν and ρ (P < 0.01; r = 0.56).     

Sex-specific differences in desiccation resistance and the use of energy metabolites as osmolytes in Drosophila melanogaster flies acclimated to dehydration stress

In the Indian subcontinent, there are significant between-population variations in desiccation resistance in Drosophila melanogaster, but the physiological basis of adult acclimation responses to ecologically relevant humidity conditions is largely unknown. We tested the hypothesis that increased desiccation resistance in acclimated flies is associated with changes in cuticular permeability and/or content of energy metabolites that act as osmolytes. Under an ecologically relevant humidity regime (~50 % relative humidity), both sexes showed desiccation acclimation which persisted for 2–3 days. However, only females responded to acclimation at ~5 % relative humidity (RH). Acclimated flies exhibited no changes in the rate of water loss, which is consistent with a lack of plastic changes in cuticular traits (body melanization, epicuticular lipid). Therefore, changes in cuticular permeability are unlikely in drought-acclimated adult flies of D. melanogaster. In acclimated flies, we found sex differences in changes in the content of osmolytes (trehalose in females versus glycogen in males). These sex-specific changes in osmolytes are rapid and reversible and match to corresponding changes in the increased desiccation resistance levels of acclimated flies. Further, the increased content of trehalose in females and glycogen in males support the bound-water hypothesis for water retention in acclimated flies. Thus, drought acclimation in adult flies of D. melanogaster involves inducible changes in osmolytes (trehalose and glycogen), while there is little support for changes in cuticular permeability.     

Diapause pupal color diphenism induced by temperature and humidity conditions in Byasa alcinous (Lepidoptera: Papilionidae)

We investigated whether diapause pupae of Byasa alcinous exhibit pupal color diphenism (or polyphenism) similar to the diapause pupal color polyphenism shown by Papilio xuthus. All diapause pupae of B. alcinous observed in the field during winter showed pupal coloration of a dark-brown type. When larvae were reared and allowed to reach pupation under short-day conditions at 18 °C under a 60 ± 5% relative humidity, diapause pupae exhibited pupal color types of brown (33%), light-brown (25%), yellowish-brown (21%), diapause light-yellow (14%) and diapause yellow (7%). When mature larvae reared at 18 °C were transferred and allowed to reach pupation at 10 °C and 25 °C under a 60 ± 5% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 91.2, 8.8 and 0.0% at 10 °C, and 12.2, 48.8 and 39.0% at 25 °C, respectively. On the other hand, when mature larvae reared at 18 °C were transferred and allowed to reach pupation at 10 °C, 18 °C and 25 °C under an over 90% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 79.8, 16.9 and 3.3% at 10 °C, 14.5, 26.9 and 58.6% at 18 °C, and 8.3, 21.2 and 70.5% at 25 °C, respectively. These results indicate that diapause pupae of brown types are induced by lower temperature and humidity conditions, whereas yellow types are induced by higher temperature and humidity conditions. The findings of this study show that diapause pupae of B. alcinous exhibit pupal color diphenism comprising brown and diapause yellow types, and suggest that temperature and humidity experienced after a gut purge are the main factors that affect the diapause pupal coloration of B. alcinous as environmental cues.     

The thermo-photoelectric (TPE) properties of the hornet cuticle: correlation with the morphological structure

The present study investigated thermoelectric phenomena in the cuticle of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). This was done in dependence on the pigment extant at various cuticular region, that is, the brown cuticle in which the primary pigment is melanin and embedded within the cuticle, and the yellow stripes in which the yellow pigment is comprised of purines and pteridines that are located in special pockets between the upper part of the cuticle and the basement membrane. The yellow pigment could be separated from the cuticle proper, but the brown pigment was not thus separable. We found that all cuticular regions of the gaster evinced a thermoelectric response, in that with rise in temperature there was a rise in the thermoelectric current, and vice versa. Additionally, the intact hornet displayed a negative photoelectric response in each of its yellow segments, so that upon illumination with UV light, the maximal current dropped by about 40-50%. Measurements taken on individual stripes in the gaster segments revealed that the photoelectric response is elicited only in the yellow stripes. In all the latter the photoelectric response persists but the maximal current level is lower than in the intact whole hornet. If the yellow pigment is detached mechanically or by bacterial incubation, the photoelectric property of the cuticle is abrogated. Likewise the photoelectric property is abrogated upon immersion of the cuticle in alcohol, even though the yellow pigment is still retained. The specific heat of the yellow stripes in the cuticle is about twice as high as that of the same stripes that had been depleted of their yellow pigment, amounting to 1.8-1.9 J/g.K vs. 0.8 J/g.K.     

Electrical properties of the oriental hornet (Vespa orientalis) cuticle

Consistent electrical and physical phenomena in the cuticle of the Oriental hornet have been recorded and measured. Active or narcotized, live hornets as well as dead ones produce, at optimal temperature for vespine biological activity, voltages of several hundred mV, currents of up to several tenths of nA, and the appropriate power. The electric resistance of the hornet cuticle and hornet silk cocoon point to their being organic semiconductors. Both of these have a large electric capacitance relative to their volume. A theoretical model is proposed to explain the capacitance phenomenon. Other phenomena observed are the production of electric energy under the influence of light and heat and also change in the various other electric properties of hornet cuticle under the influence of solar irradiation. The distribution of daily hornet activities seems to be correlated with the hours of maximal irradiation. All the afore mentioned phenomena point to the fact that there is recourse to electric energy in the daily routine of hornets and that this electric energy seems to be derived from solar energy. The conversion of the latter into the former takes place in the body of the hornet which thereby functions in the manner of a solar cell. The presence of a cuticular exoskeleton containing chitin, characterizes very many species of Invertebrates (Arthropoda). We assume that the phenomena similar to those described in this paper take place also in many other species. We hope that part of our findings will be utilizable in future developments in the fields of semiconductors and the use of solar energy.     

Differences in Cuticular Resistance in Relation to Transpiration in Tea (Camellia sinensis)

Experiments were carried out to investigate whether there were clonal differences in cuticuiar resistance to transpiration in tea (Camellia sinesis) leaves. The cuticular resistance of’ sun and shade leaves was also compared. The drying rate of detached leaves was measured and used as an estimate of cuticular resistance to transpiration. The results showed that there were clonal differences in cuticular resistance in mature and old leaves but not in young leaves. In clonal tea there appeared to be an inverse relationship between she rate of leaf growth and the cuticular resistance in mature leaves. Shade leaves had a higher cuticular resistance than sun leaves.     

Spatial distribution of Vespa velutina individuals hunting at domestic honeybee hives： heterogeneity at a local scale

Since its recent introduction into Europe, the yellow-legged hornet, Vespa velutina, has become a major predator of the domestic honeybee, Apis mellifera, but little is known about its hunting behavior. We studied V. velutina hunting behavior by a capture- mark-recapture procedure in an experimental apiary. A total of 360 hornets were captured and tagged, and we determined： （i） the number of hornets visiting the apiary and the changes in time, （ii） the average number of individual visits per half-day and the time elapsed between consecutive recaptures, and （iii） the individual and global distribution of the hornets in the apiary. More than 50% of the marked hornets were recaptured at least once, this increased to 74% in considering the first marked individuals. We estimated 350 hornets visiting the patch daily with at least 1 visit per half-day. The number of marked hornets decreased over time while the number of unmarked ones increased, suggesting a turnover of individuals. The reduction of the delay between consecutive visits indicates that hornets became more efficient over time. Most of the hornets （88%） were recaptured in front of different hives but, overall, the global distribution was aggregative. Hornets were mainly recaptured in front of 1 hive which was neither the smallest nor the biggest colony, suggesting that the major cue used by hornets is not the amount of food. We hypothesize that the defensive behavior of the honeybee colony could explain our results which may be promising to further studies.     

Influence of shell colour on the mortality rate of the land snail Arianta arbustorum under different microclimatic regimes

The mortality of phenotypic shell colour morphs and age classes of the snail Arianta arbustorum in several microclimatic conditions was recorded. An analysis of variance was performed on five factors: adaptation temperature, relative humidity, shell colour, age class and test temperature. There were no significant differences in the mortality between different adaptation temperatures or relative humidities, but the interaction of these two factors was highly significant. There were significant differences in mortality rate between test temperature and age class. The mortality of the brown morph was higher than the yellow one at all adaptation temperatures (overall, P < 0.05). There were no significant differences between the mortality rates of the two morphs at different relative humidities. The mortality of the brown morph was higher than that of the yellow at six out of seven test temperatures. Juvenile snails survived significantly better than adults at all test temperatures.     

Physical properties of flowing blood

The changes of viscosity, optical reflection and electrical resistivity of blood due to flow are dependent on the orientation and deformation of red cells. From electrical point of view, it can be assumed that blood is suspension of small insulating particles (red cells) in conductive fluid (plasma) when the frequency of supplied voltage is lower than several hundreds KHz. When blood flows, red cells deform and orient in flow direction. Therefore, flowing blood shows anisotropic electrical and optical properties. In steady flow, blood resistivity longitudinal to flow decrease with flow rate, and transverse one increases. Blood flow in living body is not steady but pulsatile. We measured both longitudinal and transverse resistivity changes, optical reflection change and viscosity change of sinusoidally flowing blood in a rectangular conduit. The results are 1) during one period of sinusoidal flow the longitudinal resistivity change is opposite to that of transverse one, 2) the waveform of reflection light change is similar to that of resistance change, and 3) minimum points of both longitudinal resistivity and viscosity changes do not appear at the moment when flow is zero but are delayed. When the amplitude of sinusoidal flow is small and oscillation frequency is high, the phase difference between the zero crossing period of flow and the period of minimum change in resistivity, increases up to 90 degrees. Viscosity of blood decreases with increase of amplitude and frequency of sinusoidal flow.     

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.     

Microclimatic adaptation and differences in food consumption and assimilation efficiency of different shell colour morphs of the land snail Arianta arbustorum

Food consumption and assimilation efficiency of different shell colour morphs adapted to various microclimatic conditions were determined. Five-factor analysis of variance (adaptation temperature, relative humidity, phenotypic shell colour, age class and time of acclimatization) was used. There are differences between different levels of adaptation temperature and relative humidity in the effect on food consumption in the two morphs. The interaction of these two factors is also significant. There is no effect of the phenotypic shell colour on the food consumption, but there is a relation between shell colour and adaptation temperature. Food consumption is greater in the juveniles. The interactions between age class and adaptation temperature or relative humidity are relevant. Acclimatization to these conditions shows a highly significant effect on the food consumption. The brown and yellow morphs of Arianta arbustorum consumed different amounts of food in relation to the adaptation temperature.
Assimilation efficiency is independent of temperature but declines at high relative humidity. There is a relation between adaptation temperature and relative humidity, but not between the phenotypic shell colour and age class factors. The yellow morphs show higher assimilation efficiencies than the brown morphs during cold adaptation to 5 °C and at the highest level of relative humidity (98%).     

Hornet cuticle: effects of short-term UV irradiation

Effects of short-term UV irradiation were investigated on various cuticular parts of workers and queens of the Oriental hornet, to wit: brown strip, yellow strip and wing. On each preparation of the afore-mentioned, a reading of the relative optical density (ROD) was taken prior to, immediately following, and 15-30 minutes after its irradiation as compared to white light irradiation. The results showed that brief UV irradiation causes changes in the ROD of hornet cuticle, and that these changes in ROD are different in brown than in yellow cuticle. Those in yellow strip are induced by the presence or absence of the active yellow pigment, whose quantity in worker cuticle is different than in queen cuticle, probably due to the various activities in which they are involved during the active season.     

The pale brown allele in Cepaea nemoralis

The pale brown colour morph in Cepaea nemoralis appears to be determined by an allele at the C (colour) locus ( C ^{P B}). Pale brown is dominant to yellow, codominant with pink and recessive to dark brown. It is linked to the B locus (which controls the presence or absence of banding on the shell), but not to the U locus, which determines whether there is one band or five. In segregations of pale brown and yellow there is a significant deficiency of pale brown, suggesting that there are differences in viability between the morphs.     

Effects of temperature, prey type and prey size on gastric evacuation in small cod and whiting

Gastric lavage was used to investigate the effects of temperature, prey type and prey size on gastric evacuation in small cod Gadus morhua and whiting Merlangius merlangus . The fish were fed to satiation and subsequently the stomach contents were sampled to determine the rate at which food was evacuated. Satiation meal size was positively related to temperature and differed between prey types. The gastric evacuation rate (GER) also tended to increase with temperature and varied with prey type. GER at temperatures of 11.3–12.7° C averaged 1.5–1.7 times higher than at 6–9.5° C. There was no significant difference (P>0.05) in the evacuation of lugworm Arenicola marina , sandeel Ammodytes spp., and herring Clupea harengus , but the GER of brown shrimp Crangon vulgaris was much slower (P<0.05). No significant changes in GER were observed when fish were fed on three different size groups of either herring or brown shrimp. In whiting, there was no significant difference in the GER of individual herring or brown shrimp when they were fed as single species meals or incorporated in meals containing a mixture of prey species.     

Rapid changes in desiccation resistance in Drosophila melanogaster are facilitated by changes in cuticular permeability

Insects can improve their desiccation resistance by one or more of (1) increasing their water content; (2) decreasing water loss rate; or (3) increasing the amount of water able to be lost before death. Female Drosophila melanogaster have previously been reported to increase their resistance to desiccation after a desiccation pre-treatment and recovery, but the mechanism of this increased desiccation resistance has not been explored. We show that female, but not male adult D. melanogaster increased their resistance to desiccation after 1 h of recovery from a 3 to 4.5 h pre-treatment that depletes them of 10% of their water content. The pre-treatment did not result in an increase in water content after recovery, and there is a slight increase in water content at death in pre-treated females (but no change in males), suggesting that the amount of water loss tolerated is not improved. Metabolic rate, measured on individual flies with flow-through respirometry, did not change with pre-treatment. However, a desiccation pre-treatment did result in a reduction in water loss rate, and further investigation indicated that a change in cuticular water loss rate accounted for this decrease. Thus, the observed increase in desiccation resistance appears to be based on a change in cuticular permeability. However, physiological changes in response to the desiccation pre-treatment were similar in male and female, which therefore does not account for the difference in rapid desiccation hardening between the sexes. We speculate that sex differences in fuel use during desiccation may account for the discrepancy.