Heat Loss and the Body Temperatures of Flying Insects

1960 ◽  
Vol 37 (1) ◽  
pp. 171-185
Author(s):  
NORMAN STANLEY CHURCH

1. Comparative measurements of body temperatures and water loss in Schistocerca gregaria showed that evaporation dissipates relatively little of the heat generated by the wing muscles during flight. 2. In perfectly dry air at 30° C, evaporation reduces the temperature excess of the pterothorax by less than 10%, or about 0.5° C. Even at 40° C, which is the highest temperature that will permit continuing flight, the reduction is only about 20%, or 1.2° C, in dry air. 3. A flying locust has no special mechanism, except cessation of flight, to protect it from overheating. Breathing is not markedly increased at high temperatures, nor is the rate of heat production reduced. 4. Very little heat is dissipated from the pterothorax by evaporation through the cuticle. The cuticle becomes permeable enough to allow substantial cooling only at temperatures well above the highest that permit flight. 5. Temperature measurements in Triphaena pronuba and Bombus lapidarius supported the idea that evaporative cooling during flight is not much more important in other well-waterproofed insects. Large changes in the humidity produced changes of less than 1° C. in the temperature excess, even at the highest air temperatures at which the insects could fly. 6. The reactions of the insects to moist and dry air are adapted to the conservation of their water rather than to rapid cooling.

1960 ◽  
Vol 37 (1) ◽  
pp. 186-212 ◽  
Author(s):  
NORMAN STANLEY CHURCH

1. The natural internal temperature gradients during flight were reproduced in various medium and large insects by mounting freshly killed specimens in a wind tunnel and heating them with a high-frequency electric current. The heat flow from the flight muscles to other parts of the body and from the body were investigated. 2. Comparison of dead and living insects showed that most of the heat transfer within the body is by conduction; circulation of the haemolymph during flight contributes little to the heat flow. 3. The temperature excess is high throughout the pterothorax in a large insect; where there are no subcutaneous air sacs it is only about 10% less at the surface of the pterothorax than at the centre. 4. Only about 5-15% of the heat generated in the flight muscles is conducted to the prothorax, head, abdomen and appendages, which remain near the temperature of the air". 5. Usually not more than 10-15% of the heat escapes from the pterothorax by long-wave radiation in a large insect flying under a clear sky. Smaller insects lose relatively more of their heat by radiation. 6. Radiation increases with the insect's temperature but it is never sufficient to give much protection against overheating. 7. Ordinarily 60-80% of the heat is dissipated from the surface of the pterothorax by convection. 8. In convection from a naked insect the relationships between heat loss, the surface temperature excess, size, and wind speed are nearly the same as in convection from a smooth cylinder or sphere, if allowance is made for turbulence in the air flow over the insect. 9. In dragonflies and denuded bees and moths heated in proportion to their pterothoracic volumes in a constant wind, the temperature excess was proportional to the 1 3-1.5 power of the average diameter of the pterothorax. 10. The coats of hair on bumble-bees, hawk moths, and noctuid moths are excellent insulators against convective heat loss. At normal flying speeds they increase the temperature excess by 50-100% or more--in a large hawk moth probably by at least 8 or 9° C. 11. The insulating value of a coat depends mostly on its density and on the size of the insect, and less on the length of the hair. 12. In dragonflies the pterothorax is insulated nearly as effectively by the subcutaneous air sacs.


1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960


1976 ◽  
Vol 23 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A. J. F. Webster ◽  
J. G. Gordon ◽  
J. S. Smith

SUMMARY1. Two series of energy balance trials were conducted with British Friesian veal calves. In the first, calves were given a milk replacer diet at three different planes of nutrition. In the second, calves were raised from about 80 to 180 kg at four air temperatures, 5°, 10°, 15° and 20°.2. The net efficiency of utilization of the milk replacer diet for growth was 0·72. The effect of body size on heat production in growing calves was best expressed by an exponent of body weight slightly but not significantly below W0·75.3. Measurements of heat production estimated from respiratory exchange and heat loss measured by direct calorimetry agreed exactly at all planes of nutrition. Heat production at zero energy retention was 675 kJ/kg W0·75 per 24 hr.4. Average daily live-weight gain and total heat loss were the same at all air temperatures. Changes during growth in the partition of heat loss into its sensible and evaporative components indicated that calves acclimated progressively to the air temperatures to which they were exposed.


1958 ◽  
Vol 194 (1) ◽  
pp. 99-108 ◽  
Author(s):  
H. T. Hammel ◽  
C. H. Wyndham ◽  
J. D. Hardy

Metabolic and thermal responses of three dogs were made in a rapid responding calorimeter at temperatures ranging from 8°C to 36°C. These dogs were acclimatized to a kennel temperature of 27°C and had critical temperatures between 23°C and 25°C. The only physiological responses to low environmental temperatures were a moderate decrease in total heat content and an increase in heat production. The tissue conductance and the cooling constant of the fur did not effectively decrease below the levels obtaining throughout the neutral zone. In a hot environment heat loss from the respiratory tract was greatly increased. Although there was a great increase in the tissue conductance in the hot environment, conductance of heat through the tissue became decreasingly important as the air temperature approached body temperature so that panting became increasingly important for maintaining thermal balance. It is concluded that the vasomotor response of the peripheral vascular system is primarily a mechanism for dissipating excess heat produced during exercise; it is practically unimportant as a heat conserving mechanism. Effective changes in the total insulation of the fur can only be achieved by changing the surface area of the body, particularly those areas which are thinly furred, and not by any important change in the fur thickness through pilomotor activity.


Author(s):  
P. Spencer Davies

When littoral animals are exposed by the receding tide they are subjected to the environmental factors of what is essentially a terrestrial environment. Of these factors desiccation (see Davies, 1969) and temperature are of paramount importance. In winter the animals may be subject to a rapid change from the relatively high temperature of the sea to a very much lower air temperature. In summertime the opposite is true and the animals will spend the dry phase in air temperatures often far in excess of sea-water temperatures. The most important temperatures from an ecological point of view, however, are the body temperatures of the animals themselves. As shown by Southward (1958) this cannot be deduced from measurements of air temperatures, since the animals are subject to heating by absorption of solar radiant energy and this in turn may be mitigated by other environmental factors.


2005 ◽  
Vol 99 (5) ◽  
pp. 1958-1964 ◽  
Author(s):  
Gordon G. Giesbrecht ◽  
Tamara L. Lockhart ◽  
Gerald K. Bristow ◽  
Allan M. Steinman

Personal floatation devices maintain either a semirecumbent flotation posture with the head and upper chest out of the water or a horizontal flotation posture with the dorsal head and whole body immersed. The contribution of dorsal head and upper chest immersion to core cooling in cold water was isolated when the confounding effect of shivering heat production was inhibited with meperidine (Demerol, 2.5 mg/kg). Six male volunteers were immersed four times for up to 60 min, or until esophageal temperature = 34°C. An insulated hoodless dry suit or two different personal floatation devices were used to create four conditions: 1) body insulated, head out; 2) body insulated, dorsal head immersed; 3) body exposed, head (and upper chest) out; and 4) body exposed, dorsal head (and upper chest) immersed. When the body was insulated, dorsal head immersion did not affect core cooling rate (1.1°C/h) compared with head-out conditions (0.7°C/h). When the body was exposed, however, the rate of core cooling increased by 40% from 3.6°C/h with the head out to 5.0°C/h with the dorsal head and upper chest immersed ( P < 0.01). Heat loss from the dorsal head and upper chest was approximately proportional to the extra surface area that was immersed (∼10%). The exaggerated core cooling during dorsal head immersion (40% increase) may result from the extra heat loss affecting a smaller thermal core due to intense thermal stimulation of the body and head and resultant peripheral vasoconstriction. Dorsal head and upper chest immersion in cold water increases the rate of core cooling and decreases potential survival time.


1986 ◽  
Vol 34 (1) ◽  
pp. 35 ◽  
Author(s):  
RV Baudinette ◽  
P Gill ◽  
M O'driscoll

Rates of oxygen consumption and means of augmenting the resultant heat production were studied in the little penguin, Eudyptula minor. Metabolic rates were lower than those predicted for a 1-kg bird, but shivering and an energy response to feeding were both present. The latter effect was independent of ambient temperatures between 2 deg and 22 deg C. The birds have limited ability to dissipate heat by evaporative water loss. About 40% of the total heat production was the maximum amount lost by this route. Cooling of expired respiratory gas provided an effective saving of heat and water. Moulting resulted in a 1.5-fold increase in metabolic rate but rates of evaporative water loss were reduced. The increase in heat production is correlated with increased thermal conductance across the body surface, as new feathers are synthesized, but body temperature is the same as in non-moulting penguins. The results suggest that increased heat loss when the birds are in water might be replaced by calorigenesis associated with the response to feeding, and by shivering, as well as by activity.


1959 ◽  
Vol 1 (1) ◽  
pp. 1-12 ◽  
Author(s):  
D. G. Armstrong ◽  
K. L. Blaxter ◽  
N. McC. Graham ◽  
F. W. Wainman

1. A series of calorimetric experiments was conducted with sheep which had fleeces ranging in thickness from 0·1 cm. to 12 cm. at environmental temperatures between 8 and 32° C. Heat production, heat loss by radiation, by convection and conduction, by vaporisation of water and due to warming food and water to body temperature were measured together with losses of energy in faeces, in urine and as methane.2. The effects of a rise in environmental temperature on digestion of the food and on the loss of energy in urine or as methane resulted in a slight rise in the metabolisable energy of the ration by 6 Cal./° C.3. Environmental temperature had a marked effect on heat production, particularly when the fleece was short. The critical temperature (i.e. the environmental temperature at which heat production was minimal) of the closely-clipped sheep varied from 24° C. at a high level of feeding to 38°C. at a sub-maintenance level of feeding. These critical temperatures are similar to that of naked, resting man but much higher than that of the pig when fed similarly.4. As the fleece grew the critical temperature fell. Thus, on a maintenance level of feeding, a sheep with a fleece of 0·1 cm. had a critical temperature of 32° C.; when the fleece had grown to 2·5 cm. the critical temperature was 13° C. while with a 12 cm. fleece the critical temperature was 0° C.5. Below the critical temperature heat losses increase more rapidly in sheep with light fleeces. Thus a heavy fleece not only depresses the critical temperature but also reduces the rate of increase of heat loss with falling temperature under sub-critical conditions.6. At environmental temperatures well below the critical, the heat losses of the sheep per unit surface were identical. Under such conditions, when the whole of the metabolisable energy of the food is used to keep the animal warm, the criterion of ration adequacy is a high content of meta-bolisable energy in small bulk.7. At environmental temperatures above 32° C. the heat production on a constant ration increased, the rise being greatest with the highest level of feeding. Consequently the net energy value of the food declined at these high environmental temperatures.8. The calorimetric experiments were supplemented by two comparative feeding trials in which the effects of normal outdoor environmental conditions on the body weight of groups of Cheviot and Blackface sheep were measured. Control groups were kept indoors in heated pens.9. During the mild winter of 1956-7 the out-wintered Blackface wethers i n full fleece did not loose any more weight than those fed the same rations indoors.10. During the more severe winter of 1957-8, Cheviot, in-lamb ewes kept on a maintenance diet gained 2·3 lb.; those kept outside on the same ration lost 3·3 lb. With Blackface, in·lamb ewes the difference between the two groups was 0·3 lb. in favour of the indoor group.11. The food utilisation of sheep is affected considerably by environmental conditions. With little fleece the critical temperature is high and even when in full fleece an effect of cold can be demonstrated under practical conditions.


1995 ◽  
Vol 268 (4) ◽  
pp. R838-R850 ◽  
Author(s):  
P. Webb

Heat regulation is presented as the physiological method of handling metabolic heat, instead of temperature regulation. Experimental evidence of heat regulation from the literature is reviewed, including more than 20 years of calorimetric studies by the author. Changes in heat production are followed by slow exponential changes in heat loss, which produce changes in body heat storage. Heat balance occurs at many levels of heat production throughout the day and night, and at each level there is a related level of rectal temperature. Heat flow can be sensed by the transcutaneous temperature gradient. The controller for heat loss appears to operate like a servomechanism, with feedback from heat loss and possibly feedforward from heat production. Physiological responses defend the body heat content, but heat content varies over a range that is related to heat load. Changes in body heat content drive deep body temperatures.


1967 ◽  
Vol 47 (3) ◽  
pp. 561-587 ◽  
Author(s):  
TORKEL WEIS-FOGH

1. New methods were designed for the simultaneous determination of the unidirectional flow of air and the total abdominal pumping in flying locusts, for measurements of the potential and the actual rate of flow caused by thoracic pumping, and for an independent estimate of the total ventilation of the flight system. 2. During rest, flight and recovery in the desert locust, the unidirectional flow caused by abdominal pumping remains small and almost constant at 30 l. air/kg./hr., in through the thoracic spiracles and out through the abdominal ones. The total pumping amounts to about 180 l./kg./hr. in flight of which 70 l. ventilate the thorax and 80 l. the other paits of the body. 3. Abdominal pumping can be blocked reversibly or reduced to insignificance without impairing the wing movements of the desert locust. 4. During average horizontal flight of the desert locust, the thoracic ventilation is about 320 l. air/kg./hr. of which 250 l. are moved by the thoracic pump, but the capacity of this pump is 760 l./kg./hr. and can be increased to at least 950 l./kg./hr. The relatively low efficiency is likely to increase when the abdominal air sacs are deflated due to ingested food, fat or eggs, i.e. when the animal has to lift more. 5. The pressure changes caused by the thoracic pumping only amount to 10-25 mm. H2O and are of no mechanical significance for the moving wings. 6. Draught ventilation due to a Bernoulli effect is of no significance in locusts and probably not in dragonflies and wasps. 7. The oxygen in the thorax of flying locusts is reduced by about 5.5 % relative to the atmosphere at sea level. 8. At small to medium relative humidities, and at temperatures between 25 and 30° C. at sea level, the rate of ventilation permits sustained flight of the desert locust without risk of desiccation (Fig. 14). In order to retain a positive water balance at higher air temperatures the locusts must fly at high altitude, and 3 km. is estimated as a maximum for sustained, active flight. 9. Large dragonflies (Aeshna spp.) depend almost exclusively on thoracic pumping during flight, while large wasps (Vespa crabro) depend on abdominal pumping. For both types the metabolic rate is about 100 kcal./kg./hr. during level flight.


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