608 Cutn PInG 
9.7 per cent in August. The salt pools contain several algae and several 
protozoa, together with some anima! pollution. 
2. The growth of the larva is largely influenced by temperature and 
the presence of salt in water. 
3. The larva moves by crawling, wriggling, floating, and dropping. 
Its respiration is at the surface. Its food consists of algae with few protozoa. 
It prefers to live in stagnant and shallow water, with the amount of salt 
ranging between 1 and 8 per cent and a solution of from 4- to 5- per-cent 
salt in the optimum. 
4, The larva can live in a limited area of air. It can endure the variation 
of temperature from 0° to 40° C. It can survive drought for five days. 
5. It is significant with the larva that its specific gravity is less than 
unity. 
6. Any mechancial injury which breaks the hypodermis proves fatal 
to the larva. 
7. Pupation is characterized by the perching habit. The pupal period 
lasts from two to eleven days in the laboratory and from four to five months 
in the field. High temperature in addition to desiccation is very 
detrimental. 
8. The food of the adult is the same as that of the larva. The adult 
prefers to stay on the surface of still water. Excessive heat is very detri- 
mental, but excessive rainfall is beneficial. Only heavy frost has a killing 
effect upon the newly emerged adult. The adults disappear. entirely in 
winter when snow covers the ground. 
9. The egg is elongated oval with a reticulated surface. Hatching 
takes place in fresh water as well as in salt water. The development of 
the egg is affected by temperature. 
10. The habit, the adaptation, the coloration, and the body structure 
of all stages are protective. Domestic fowls and water striders were the 
only enemies observed. 
11. The dispersal of this species takes place during the pupal stage and 
is probably achieved by artificial transportation. 
12. The flies appear in May or June. High temperature and high 
humidity in late spring make for an early appearance. Frequent rains 
favor abundance of them throughout the summer and autumn seasons. 
13. This species winters usually in the larval and pupal stages, although 
a few adults may live through the winter in hibernation. 
