Thoracic Temperature Stabilization byn Blood Circulation in a Free-Flying Moth.
01 May 1970-Science (American Association for the Advancement of Science)-Vol. 168, Iss: 3931, pp 580-582
TL;DR: The sphinx moth, Manduca sexta, maintains its thoracic temperature within a degree of 42�C while in free flight over a range of air temperatures from about 17� to 32�C, while tying off the dorsal vessel abolishes temperature control.
Abstract: The sphinx moth, Manduca sexta, maintains its thoracic temperature within a degree of 42°C while in free flight over a range of air temperatures from about 17° to 32°C. Tying off the dorsal vessel abolishes temperature control. Moths with tied off vessels overheat and then stop flying at air temperatures of about 23°C. However, flight at this temperature is possible when the thoracic scales are removed. The mechanism of temperature control involves transfer of the heat produced in the thorax to the blood pumped from the dorsal vessel, and the subsequent dissipation of this heat when the blood returns to the relatively cool abdomen.
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TL;DR: The data on metabolic scope, power requirements for flight, Q 10 and body mass are used to develop equations that predict thoracic temperature during flight for both sphingids and saturniids.
Abstract: A method for instantaneous measurement of oxygen consumption in an open flow respirometry system is described. During pre-flight warm-up in both sphingids and saturniids, oxygen consumption reaches levels 20 to 70 times resting values. V O O2 required to maintain the thorax at flight temperature by intermittent wing-quivering and fluttering is about one-third the maximum V O O2 during warm-up. The Q 10 of resting V O O2 averages 2·4 in both sphingids and saturniids. At any given thoracic temperature, V O O2 during post flight-cooling exceeds V O O2 at rest. Factorial scope (maximum V O O2 ÷resting V O O2 ) during warm-up is independent of mass and thoracic temperature. In sphingids it averages 39, in saturniids, 43. Absolute metabolic scope in both groups increases with thoracic temperature and is roughly proportional to V O O2 . In saturniids about 49% of the heat produced during warm-up is stored in the thorax; in sphingids the figure is about 73%. The data on metabolic scope, power requirements for flight, Q 10 and body mass are used to develop equations that predict thoracic temperature during flight for both sphingids and saturniids.
430 citations
Cites background from "Thoracic Temperature Stabilization ..."
...During pre-flight warm-up in moths, most of the heat produced is retained within the thorax, while the abdomen remains at or near ambient temperature (Hanegan & Heath, 1970; Heinrich, 1970; Heinrich & Bartholomew, 1971; Bartholomew & Casey, 1973)....
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...The rapidity of the decline in thoracic temperature immediately after the cessation of flight (Bartholomew & Epting, 1975 a, b) suggests the presence of facilitated cooling, presumably by means of circulation of haemolymph to the abdomen (Heinrich 1970; Heinrich & Bartholomew, 1971)....
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TL;DR: In both temperate and tropical regions, high rates of adult reproduction in a given environment may not be realized if occasional, high temperatures prevent survival to maturity, suggesting that considering the differing responses of multiple life stages is essential to understand the ecological and evolutionary consequences of climate change.
Abstract: Many organisms have complex life cycles with distinct life stages that experience different environmental conditions. How does the complexity of life cycles affect the ecological and evolutionary responses of organisms to climate change? We address this question by exploring several recent case studies and synthetic analyses of insects. First, different life stages may inhabit different microhabitats, and may differ in their thermal sensitivities and other traits that are important for responses to climate. For example, the life stages of Manduca experience different patterns of thermal and hydric variability, and differ in tolerance to high temperatures. Second, life stages may differ in their mechanisms for adaptation to local climatic conditions. For example, in Colias, larvae in different geographic populations and species adapt to local climate via differences in optimal and maximal temperatures for feeding and growth, whereas adults adapt via differences in melanin of the wings and in other morphological traits. Third, we extend a recent analysis of the temperature-dependence of insect population growth to demonstrate how changes in temperature can differently impact juvenile survival and adult reproduction. In both temperate and tropical regions, high rates of adult reproduction in a given environment may not be realized if occasional, high temperatures prevent survival to maturity. This suggests that considering the differing responses of multiple life stages is essential to understand the ecological and evolutionary consequences of climate change.
390 citations
Cites background from "Thoracic Temperature Stabilization ..."
...During flight, moths maintain thoracic temperatures of 38–428C over air temperatures from 108C to 358C (Heinrich 1970)....
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...Generating enough power for flight is supported in part by high thoracic temperatures, the heat for which comes from muscle contractions (a form of periodic endothermy) (Heinrich 1970)....
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TL;DR: The insects' thermal adaptations may not differ as much from those of vertebrates as previously supposed when size, anatomy, and energy requirements are taken into account.
Abstract: On the basis of body weight, most flying insects have higher rates of metabolism, and hence heat production, than other animals However, rapid rates of cooling because of small body size in most cases precludes appreciable endothermy The body temperature of small flies in flight is probably close to ambient temperature, and that of flying butterflies and locusts is 5 degrees to 10 degrees C above ambient temperature Many moths and bumblebees are insulated with scales and hair, and their metabolism during flight can cause the temperature of the flight muscles to increase 20 degrees to 30 degrees C above ambient temperature Curiously, those insects which (because of size, insulation) retain the most heat in the thorax during flight, also require the highest muscle temperature in order to maintain sufficient power output to continue flight The minimum muscle temperature for flight varies widely between different species, while the maximum temperature varies over the relatively narrow range of 40 degrees to 45 degrees C As a consequence, those insects that necessarily generate high muscle temperatures during flight must maintain their thoracic temperature within a relatively narrow range during flight Active heat loss from the thorax to the abdomen prevents overheating of the flight motor and allows some large moths to be active over a wide range of ambient temperatures Bumblebees similarly transfer heat from the flight musculature into the abdomen while incubating their brood by abdominal contact Many of the larger insects would remain grounded if they did not actively increase the temperature of their flight muscles prior to flight Male tettigoniid grasshoppers elevate their thoracic temperature prior to singing In addition, some of the social Hymenoptera activate the "flight" muscles specifically to produce heat not only prior to flight but also during nest temperature regulation During this "shivering" the "flight" muscles are often activated in patterns different from those during flight The muscles contract primarily against each other rather than on the wings However, the rate of heat production during shivering and flight is primarily a function of the action potential frequency rather than of the patterns of activation Thermoregulation is a key factor in the energetics of foraging of some of the flower-visiting insects The higher their muscle temperature the more flowers they can visit per unit time When food supplies are ample, bees may invest relatively large amounts of energy for thermoregulation While shivering to maintain high body temperatures during the short intervals they are perched on flowers (as well as while in the nest), bumblebees often expend energy at rates similar to the rates of energy expenditure in flight Unlike vertebrates, which usually regulate their body temperature at specific set points, the body temperature of insects is labile It often appears to be maintained near the lower temperature at which the muscles are able to perform the function at hand The insects' thermal adaptations may not differ as much from those of vertebrates as previously supposed when size, anatomy, and energy requirements are taken into account
279 citations
TL;DR: The aerodynamic mechanisms employed durng the flight of the hawkmoth, Manduca sexta, have been investigated through smoke visualization studies with tethered moths and stereophotographs suggest that the bound circulation may not be reversed between half strokes at the fastest flight speeds.
Abstract: The aerodynamic mechanisms employed durng the flight of the hawkmoth, Manduca sexta , have been investigated through smoke visualization studies with tethered moths. Details of the flow around the wings and of the overall wake structure were recorded as stereophotographs and high–speed video sequences. The changes in flow which accompanied increases in flight speed from 0.4 to 5.7 m s−1 were analysed. The wake consists of an alternating series of horizontal and vertical vortex rings which are generated by successive down– and upstrokes, respectively. The downstroke produces significantly more lift than the upstroke due to a leading–edge vortex which is stabilized by a radia flow moving out towards the wingtip. The leading–edge vortex grew in size with increasing forward flight velocity. Such a phenomenon is proposed as a likely mechanism for lift enhancement in many insect groups. During supination, vorticity is shed from the leading edge as postulated in the ‘flex’ mechanism. This vorticity would enhance upstroke lift if it was recaptured diring subsequent translation, but it is not. Instead, the vorticity is left behind and the upstroke circulation builds up slowly. A small jet provides additional thrust as the trailing edges approach at the end of the upstroke. The stereophotographs also suggest that the bound circulation may not be reversed between half strokes at the fastest flight speeds.
239 citations
References
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TL;DR: In this article, the heat flow from the flight muscles to other parts of the body and from the body were investigated and it was shown that most of the heat transfer within the body is by conduction; circulation of the haemolymph during flight contributes little to heat flow.
Abstract: 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 insect9s 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.
173 citations
TL;DR: It is suggested that a definite relationship may exist between temperature and the maximum work of which a muscle is capable.
Abstract: Temperatures have been measured by means of thermojunctions at several points in the body of insects preparing for flight.
In butterflies ( Vanessa ), moths and bumble bees ( Bombus ), preparation consists in vibratory movements of the wing raising the temperature of the wing muscles usually above 30°C. In lamellicorn beetles ( Geotrupes ) there are no visible movements of the wings, but the vibrations can be demonstrated by leading off action potentials from the muscles. The heat production takes place always in the wing muscles, but there is a gradual and much slower increase in the temperature of the rest of the body.
The muscle temperature necessary for flight is high (above 32°) and nearly constant in bad fliers ( Geotrupes ), while the good fliers can fly at different temperatures, Vanessa from about 20 up to 42°. Even in the latter type a high rate of flight can be attained only when the wing muscles have become heated above 35°.
The heat production in the vibrating muscles can be estimated from the temperature increment during the heating process combined with the decrement during subsequent cooling. It increases rapidly with increasing temperature. The final value found in Vanessa just before flight at 34° corresponds to a metabolism of 30 l. O2/kg./hr. The metabolism in acutal flight reaches much higher values.
It is suggested that a definite relationship may exist between temperature and the maximum work of which a muscle is capable.
Owing to war conditions, the authors have been unable to submit a corrected proof prior to publication.
139 citations
TL;DR: A model of the central nervous interactions which generate the observed motor patterns is proposed and it is postulated that a small group of positively coupled neurons produces bursts of impulses at the wingbeat frequency and that these groups interact to generate the phase relationships seen during warm-up and flight.
Abstract: 1. The patterns of muscle activity during warm-up were compared to those of flight. In the skipper Hylephila phylaeus and in the hawk moths Celerio lineata and Mimas tiliae the intervals between bursts of muscle potentials are the same as the wingbeat periods of flight at the same thoracic temperature, and the burst length is the same as in flight. In saturniids the period and burst length are both shorter during wing-vibrating than during flight. 2. During wing-vibrating the amplitude of the wing movement is small, and some of the muscles which are antagonists in flight are active simultaneously. In Hylephila phylaeus and Celerio lineata there is a phase change between some synergistic muscles, while some antagonistic pairs retain the phase relationships of flight. During wing-vibrating in Mimas tiliae and in saturniids all the motor units sampled were active at the same time. 3. In M. tiliae a variety of phase relationships intermediate between those of wing-vibrating and flight were observed, including a case of ‘relative co-ordination’ between motor units in the mesothorax. The results exclude the possibility that a single pace-making centre drives the motor neurons in the flight pattern. 4. A model of the central nervous interactions which generate the observed motor patterns is proposed. It is postulated that a small group of positively coupled neurons produces bursts of impulses at the wingbeat frequency and that these groups interact to generate the phase relationships seen during warm-up and flight.
103 citations
TL;DR: 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, and 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.
Abstract: 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.
92 citations
TL;DR: It is concluded that the frequency of the wing beat is determined principally by the wing loading, whilst variations in the other parameters of theWing stroke provide the ‘fine control’ of flight regulation required during flight and whilst hovering.
Abstract: 1. Moths belonging to the family Sphingidae are not capable of controlled flight until the temperature of the flight muscle has been raised by a preliminary period of vibrating the wings. 2. The flight-temperature of forty-five specimens of Deilephila nerii varied between 34 and 45° C., but individuals always flew at the same temperature. 3. The temperature inside the thorax rose at a mean rate of 4.2° C./min. 4. Alteration of the ambient temperature affects the duration of the warming period but not the flight-temperature. 5. The flight-temperature shows a positive correlation with the wing loading. In Deilephila and two other genera of similar dimensions, an increase of 50 mg. in the wing loading corresponds to a rise of 5.75° C. in the flight-temperature. 6. A method of measuring the rise in wing-beat frequency during the warming period is described. The thoracic temperature increases linearly with the frequency. 7. It is concluded that the frequency of the wing beat is determined principally by the wing loading, whilst variations in the other parameters of the wing stroke provide the ‘fine control’ of flight regulation required during flight and whilst hovering.
74 citations