Saline lakes are bodies of water that have a high concentration of dissolved salts. These lakes are commonly found in semi-arid and arid regions around the world. The main reason for their presence in these regions is the high rate of evaporation.

1. Arid and Semi-Arid Regions:
Saline lakes are typically found in arid and semi-arid regions, which are characterized by low annual rainfall and high temperatures. These regions experience high rates of evaporation due to the hot and dry climate. As a result, water bodies in these areas tend to lose more water through evaporation than they gain through precipitation.

2. Rate of Evaporation:
The high rate of evaporation in arid and semi-arid regions is a key factor in the formation of saline lakes. When water evaporates from a lake, it leaves behind the dissolved salts, which become more concentrated in the remaining water. Over time, this process leads to the buildup of salts in the lake, making it saline.

3. Precipitation and Runoff:
In arid and semi-arid regions, the amount of precipitation is generally low. The limited rainfall is often insufficient to replenish the water lost through evaporation. Additionally, the low permeability of the soil in these regions means that there is minimal runoff into lakes and rivers, further reducing the input of fresh water.

4. Concentration of Salts:
As the water in a lake evaporates, the salts become more concentrated. This increase in salinity is due to the fact that the dissolved salts do not evaporate along with the water. Instead, they are left behind, leading to a higher concentration of salts in the remaining water.

5. Crustaceans and Salinity:
While it is true that certain crustaceans can contribute to the salinity of a lake, this is not the main reason for the presence of saline lakes in arid and semi-arid regions. Crustaceans such as brine shrimp and Artemia can tolerate high salinity levels and are often found in saline lakes. However, their presence does not directly cause the water to become salty.

In conclusion, the main reason saline lakes are found in semi-arid and arid regions is the high rate of evaporation. The combination of low rainfall, high temperatures, and limited runoff results in a net loss of water through evaporation, leading to the concentration of salts and the formation of saline lakes.