The king cobra : Longest venomous snake in the world

The king cobra (Ophiophagus hannah) is the world's longest venomous snake, with a length up to 5.6 m (18.5 ft). This species, which preys chiefly on other snakes, is found predominantly in forests from India through Southeast Asia to Indonesia and the Philippines. Despite the word "cobra" in its name, this snake is not a member of Naja ("true cobras") but belongs to its own genus. The king cobra is considered to be a dangerous snake. It has cultural significance as well.
The king cobra averages at 3 to 4 m (9.8 to 13 ft) in length and typically weighs about 6 kg. The longest known specimen was kept captive at the London Zoo, and grew to around 18.5 to 18.8 ft (5.6 to 5.7 m) before being euthanized upon the outbreak of World War II. The heaviest wild specimen was caught at Royal Island Club in Singapore in 1951, which weighed 12 kilograms and measured 4.8 m (16 ft), though an even heavier captive specimen was kept at New York Zoological Park and was measured as 12.7 kilograms at 4.4 m (14 ft) long in 1972. The length and mass of the snakes highly depend on their localities and some other factors. Despite their large sizes, typical king cobras are fast and agile.
The skin of this snake is either olive-green, tan, or black, and it has faint, pale yellow cross bands down the length of the body. The belly is cream or pale yellow, and the scales are smooth. Juveniles are shiny black with narrow yellow bands  (can be mistaken for a banded krait, but readily identified with its expandable hood). The head of a mature snake can be quite massive and bulky in appearance, though like all snakes, they can expand their jaws to swallow large prey items. It has proteroglyph dentition, meaning it has two short, fixed fangs in the front of the mouth which channel venom into the prey like hypodermic needles. The male is larger and thicker than the female. The average lifespan of a wild king cobra is about 20 years.

King Cobra : Cultural significance

In Burma, king cobras are often used by female snake charmers. The charmer is usually tattooed with three pictograms, using an ink mixed with snake venom; superstition holds that it protects the charmer from the snake. The charmer kisses the snake on the top of its head at the end of the show.
In India, the king cobra is believed to possess exceptional memory. According to a myth, the picture of the killer of a king cobra stays in the eyes of the snake, which is later picked up by the partner and is used to hunt down the killer for revenge. To prove this theory, a king cobra was captured and left free in an enclosure which had small openings. Numerous people stood in front of the openings but the snake rose to its full height and locked eyes only with the captor. Due to this myth, whenever a cobra is killed, especially in India, the head is either crushed or burned to damage the eyes completely.

King Cobra : Venom

The venom of the king cobra consists primarily of neurotoxins, but it also contains cardiotoxic and some other compounds. Similar to other venomous creatures, toxic constituents inside the venom are mainly proteins and polypeptides.
This species is capable of delivering a fatal bite and a large quantity of venom can be injected with a dose anywhere from 200–500 mg on average, and up to 7 ml. Engelmann and Obst (1981) list the average venom yield at 420 mg (dry weight). A large quantity of antivenom may be needed to reverse the progression of symptoms developed if bitten by a king cobra.
During a bite, venom is forced through the snake's 1.25 to 1.5 cm (0.49 to 0.59 in) fangs into the wound, and the toxins begin to attack the victim's central nervous system. Symptoms may include severe pain, blurred vision, vertigo, drowsiness, and paralysis. Envenomation progresses to cardiovascular collapse, and the victim falls into a coma. Death soon follows due to respiratory failure. Moreover, envenomation from king cobras is clinically known to cause renal failure as observed from some snakebite precedents of this species.
The mortality rate and death time resulting from a bite can vary sharply with many factors including the quantity of venom delivered, the site of bite and the health state of the victim. Data provided by different sources which may come from different regions could also have a significant difference: while a report mentions that many bites from king cobras involve non-fatal amounts of venom, another report of clinical statistics released by the South Indian Hospital reveals that two-thirds of the bitten patients had received severe bites from this species. According to the University of Adelaide Department of Toxicology, an untreated bite has a mortality rate of 50-60%. Bites from a king cobra may result in a rapid fatality which can be as early as 30 minutes after envenomation, depending upon the nature and severity of the bites.
There are two types of antivenom made specifically to treat king cobra envenomations. The Red Cross in Thailand manufactures one, and the Central Research Institute in India manufactures the other; however, both are made in small quantities and are not widely available. Ohanin, a protein component of the venom, causes hypolocomotion and hyperalgesia in mammals. Other components have cardiotoxic, cytotoxic and neurotoxic effects. In Thailand, a concoction of alcohol and the ground root of turmeric is ingested, which has been clinically shown to create a strong resilience against the venom of the king cobra, and other snakes with neurotoxic venom.
Diet
The king cobra's generic name, Ophiophagus is a Greek-derived word which means "snake-eater", and its diet consists primarily of other snakes, including rat snakes, small pythons and even other venomous snakes such as various members of the true cobras (of the genus Naja), and even the much more venomous members of the krait family. When food is scarce, they may also feed on other small vertebrates, such as lizards, birds, and rodents. In some cases, the cobra may "constrict" its prey, such as birds and larger rodents, using its muscular body, though this is uncommon. After a large meal, the snake may live for many months without another one because of its slow metabolic rate. The king cobra's most common meal is the rat snake; pursuit of this species often brings king cobras close to human settlements.
As I told in “Cultural significance”  there are many myths about these snakes than others. Also they are dangerous like as black mambas!

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