Water Relationships of Aphis Fabae Scop. During Tethered Flight

Abstract

1. Water content varies from 64 to 73% of the total body weight and 72-76% of the fatless body weight of 24 hr. old unflown alatae of Aphis fabae. 2. Water loss during flight may be attributed to evaporation and excretion. A mean of 0.07 mg. water is lost per aphid during a 6 hr. tethered fligh a 25-26° C. and 57-82% R.H., corresponding to c. 9% body weight; at least 66% of the loss (c. 1% body weight/hr.) is by evaporation. 3. Excretion during fligh is not affected by relative humidity differences over the range 41-75% at 25%26° C., but the relative amounts of water lost during prolonged flight are inversely related to relative humidity, because of the effect of humidity on evaporation. 4. Proportion of water in he body does no change significantly during tethered fligh. Mean percentage water to total body weight increases from c. 68-69% during 6 hr.; mean percentage water to fatless body weight decreases from c. 74 to 73%. 5. Water loss is evidently not a limiting factor to fligh in atmospheres of saturation deficit less than c. 23 mm. Hg.