J. K. Nayar

The fuel for sustained mosquito flight.

Abstract Males and females of Aedes sollicitans and Aedes taeniorhynchus were flown on a flight mill and analysed for duration and distance of flight, and for utilization of triglycerides, glycogen, and trehalose. Unfed, blood-fed, and glucose-fed mosquitoes were flown either to exhaustion or for 1 hr. Triglycerides and other lipids were not used for flight. Utilization of carbohydrate was 0·08 to 0·10 cal/1000 m or 27 to 37 cal/hr per g, whether calculated from the utilization of glycogen (in unfed and blood-fed mosquitoes) or from the production of carbon dioxide (in glucose-U- 14 C fed mosquitoes). The maximum metabolic rate during flight was four to five times that of non-fed controls. In sugar-fed mosquitoes, glycogen and triglycerides accumulated during flight. Glycogen was not utilized as a flight substrate as long as sugar was available. Starved mosquitoes and mosquitoes flown to exhaustion could resume vigorous flight immediately after a sugar meal. Trehalose did not change during vigorous flight and made a negligible contribution to exhaustive flight. In unfed mosquitoes, the flight following a rest period after exhaustion was sustained by residual glycogen; no increase in glycogen took place while resting. The significance of these results to migration and dispersal in mosquitoes is discussed.

Turn-over of diglycerides during flight and rest in the moth Spodoptera frugiperda

In the unfed moth the diglyceride pool (0.5 mg.) is in a steady state during flight and rest. When the diglycerides were labelled, a specific activity-time curve showed that the pool turned over in approximately 1 hour during flight and in 6 hours during rest. The turn-over was sufficient to account for the energy used in flight as well as at rest, and is consistent with the hypothesis that diglycerides function in lipid transport. After flights sustained to exhaustion, radioactivity in diglycerides and in triglycerides had diminished, although the total amount of lipids was not lower than at rest. This suggests that flight stimulates the de novo synthesis of lipids.

Long-term regulation of sucrose intake by the female mosquito, Aedes taeniorhynchus

Abstract Newly emerged female Aedes taeniorhynchus were maintained in cups provided with potometers containing 5, 10, and 25% sucrose solutions. Mortality and the ab lib. intake of sucrose were recorded daily and groups were sampled at regular intervals for analysis of energy reserves. After a week of relatively substantial intake of sucrose at all three concentrations, a constancy in daily intake at much lower levels was observed during the next 4 weeks. The caloric intake was highest in the 25% sucrose solution group. There were no differences in mortality rates at these concentrations. Glycogen (0·7–1·0 cal/female) and triglycerides (3·5dash4 cal/female) reserves reached maximum levels after the first week and stabilized thereafter on all three concentrations. In this species the stabilization in intake of sucrose solution after the first week is correlated with the maximum accumulation of stored energy reserves as opposed to decreased activity or subtle changes associated with senescence.

Direct use of carbohydrates during sustained flight in the moth, Spodoptera frugiperda

Abstract The hypothesis that Lepidoptera use carbohydrates for flight energy without previous conversion to fat was investigated in Spodoptera frugiperda . Moths were fed on a single meal of 10 mg. [U 14 C] glucose and flown in a sealed flight mill. About 25 per cent of the fed glucose was converted in 4 hours to trehalose and glycogen, at rest as well as in flight. When moths were flown immediately after feeding, the specific activity of the expired CO 2 was several times that of any of the lipid fractions. This suggests the direct use of carbohydrates in flight. However, carbohydrates did not constitute the only flight substrate, since the specific activity of expired CO 2 remained considerably below that of the fed sugar. Twenty-four hours after feeding, elevated carbohydrate levels persisted, but no glucose remained. When these postabsorptive moths were flown, trehalose and glycogen levels dropped. Since flight did not increase the specific activity of any lipid fraction, these carbohydrates were used without conversion to fat. In the postabsorptive moths the total amount of lipids did not decrease, but the specific activity of triglycerides diminished 40 per cent during 6 hours of flight. This suggests that utilization of these lipids during flight was compensated by resynthesis, not from the high specific activity carbohydrates but from material with a low specific activity.

Flight performance and metabolism of the moth Spodoptera frugiperda

Abstract Tethered moths were flown continuously for 4 to 7 hr in a sealed flight mill which allowed the trapping of CO2 and the recording of distance flown. The respiratory rate was approximately 10 cal/km per g or 30 cal/hr per g in flight, and 5 cal/hr per g at rest. In two experiments, the triglyceride content in flown moths had decreased sufficiently to account for the respiratory CO2. In subsequent experiments with a different strain of the same species, the lipid content did not diminish significantly during flight. During sugar absorption, the respiratory rate at rest was several times higher than in unfed moths. Glycogen and trehalose levels rose sharply during absorption, both at rest and in flight.

Utilization of injected glucose by the tsetse fly (Glossina) and the stable fly (Stomoxys)

Abstract A massive dose of injected glucose was oxidized by the stable fly (Stomoxys calcitrans) at a rate of 5·5 cal/hr per g and by the tsetse fly (Glossina austeni and Glossina morsitans) at a rate of 3 cal/hr per g. This suggests that there are no distinct differences in the glycolytic pathways of these two flies.