Concrete dams, which do not have any steel reinforcement, have a much longer service life than reinforced concrete struc-tures exposed to weather. The oldest concrete dams are about 120 years old. masonry dams can be much older and still be in service.ut at the same time, it can also be very short if some of the safety-relevant elements are no longer functioning properly.an example for uncontrolled safety decrease is the 272m high Enguri arch dam (the worldâs highest arch dam) in Georgia, which was completed in 1984.
As it turns out, mosquitoes do play an important role in a variety of ecosystems. For example, each year when the snow melts in the Arctic tundra, mosquitoes hatch from their eggs and make up a significant part of the biomass. Some scientists believe these insects serve as an important food source for migratory birds.
Since the housefly's mouth parts are designed to sponge and ingest liquefied food, it's just a matter of turning on the suction. The food goes straight into the fly's stomach. Oxford Scientific/Photolibrary/Getty Images. A housefly uses its proboscis to eat a piece of sugar. Solid food is slightly more difficult. Houseflies can't bite or chew -- they simply don't have the proper equipment. So if forced to contend with something more solid, like a grain of sugar or dried blood, houseflies must employ a different tactic. First, the housefly scrubs the dry food substance with the bristles on the end of its proboscis.