Aspidiotus destructor is a well-known pest of several tropical crops, mainly coconuts and bananas, and is present in most tropical countries. In Fiji it was a serious menace to the copra industry, and attempts to control it by biological means were made in 1920, when parasites were introduced from Tahiti ; in 1927, when other parasites were introduced from Java ; and in 1928, when predators were imported from Trinidad. The introductions made in 1920 and 1927 proved of no economic value, but the predators from Trinidad completely suppressed the pest in 1928 and 1929, and have controlled it most satisfactorily ever since.

Newly Hatched Tsetse (0–1 day old).

1. Neither species is affected by daily maximum temperatures of 95–102°F.

2. Possibly the death of any weakly tsetse is accelerated by a temperature of 102·5°F.

3. The critical zone for G. tachinoides is 103° to 105°F., but at the latter temperature 100 per cent. mortality is only assured if this maximum lasts for about 100 minutes.

4. The critical zone for G. submorsitans is 103·5° to 106°F.

5. If maintained for 60 minutes, 106°F. assures 100 per cent. mortality among young flies of both species.

Old Tsetse (over 10 days old).

6. The critical zone for G. tachinoides is 102° to 105·5°F.

7. The critical zone for G. submorsitans is 102·5° to 106°F.

8. The sudden increase in mortality among tsetse upon very hot days would appear to be directly due to the maximum temperature having entered the critical zone, and not to excessively low humidity or very high evaporation.

9. The critical zone for old flies starts at about 1°F. lower than for newly hatched flies.

10. G. tachinoides is rather more susceptible to high maximum temperatures than is G. submorsitans ; results also suggest that G. tachinoides cannot withstand an exposure of long duration at high temperatures as well as G. submorsitans.

1. The increase in weight of flies of both sexes is followed on several diets. Unfed flies and flies fed on water alone or on meat and water lose weight. Males fed on meat, sugar and water, or on sugar and water, increase in weight rapidly during the first day of adult life and then lose weight until they die. Females fed on sugar and water increase in weight rapidly for the first day and then more slowly until the twelfth day, when they commence to lose weight until death occurs. A similar rapid increase in weight on the first day occurs in females fed on meat, sugar and water, but a second period of rapid increase occurs between the fourth and sixth days. The first period corresponds to the growth of the imaginal fat-body and the second to the growth of the ovaries. The percentage dry weight of flies fed on meat, sugar and water and on sugar and water increases rapidly at first but then decreases slowly until death occurs.

2. The disappearance of the pupal fat-body cells and the growth of the imaginal fat-body on several diets is described. It is suggested that the inclusions of the pupal fat-body cells are transferred to the rapidly growing imaginal fat-body.

3. The hypothesis is put forward that the abdominal air-sacs in flies of the Muscid type have but little respiratory function and are chiefly concerned in

(a) preserving the increased volume of the newly-emerged fly ;

(b) providing ample space within the abdomen for growth of the imaginal fat-body in the male and for the fat-body and ovaries in the female, both of which organs increase greatly in size.