M. fulvius is generally less than in total length. The maximum reported total lengths are for a specimen in Florida and . Males have longer tails than females, but females reach a greater total length. The dorsal scales are smooth, and are in 15 rows at midbody. The ventral scales number 197-217 in males and 219–233 in females. There are 40–47 subcaudals in males and 30–37 in females. The anal plate is divided. The color pattern consists of a series of rings that encircle the body: wide red and black rings separated by narrow yellow rings. The head is black from the rostral scale to just behind the eyes. The red rings are usually speckled with black. People who live in its natural range are often taught a folk rhyme as children such as: "Red next to black, safe from attack; red next to yellow, you're a dead fellow," or "Red touching black, friend of Jack; red touching yellow, you're a dead fellow", or simply "red and yellow kill a fellow". These rhymes are useful in teaching children to distinguish king snakes, which are considered helpful predators of vermin such as rats and mice, from the venomous coral snake, which should only be handled by an experienced biologist or herpetologist. However, this rhyme is only applicable to the United States species, and cannot be used reliably in the Caribbean, or Central or South America.
Common names
Among the many common names for M. fulvius are eastern coral snake, American cobra, candy-stick snake, common coral snake, coral adder, Elaps harlequin snake, Florida coral snake, harlequin coral snake, North American coral snake, red bead snake, thunder-and-lightning snake, and, in Spanish, serpiente-coralillo arlequín.
M. fulvius eats lizards, frogs, and smaller snakes, including other coral snakes.
Reproduction
Females of M. fulvius are reported to lay three to 12 eggs in June that hatch in September. Neonates are in length.
Venom
The venom of M. fulvius is a potent neurotoxin with a median of 1.3 mg/kg SC. Envenomation causes rapid paralysis and respiratory failure in prey. In humans, symptoms include slurred speech, double vision, and muscular paralysis eventually leading to respiratory failure. M. fulvius bites and fatalities are very rare. Only two documented fatalities were attributed to this species in the 1950s, and only one has been reported since Wyethantivenin became available for it in the 1960s. The snakes have a mortality rate between 5–20% The most recent fatality attributed to the eastern coral snake occurred in 2006. The victim failed to seek proper medical attention and died several hours after being bitten, becoming the first fatality caused by M. fulvius in over 40 years. M. fulvius does not account for many cases of snakebite in the U.S., with only about 100 bites each year. The snake is considered secretive and generally reluctant to bite, and envenomation is thought to occur in only 40% of all bites. Unlike New Worldpit vipers, this New World coral snake cannot control the amount of primarily neurotoxic venom injected. Dry bites often result from a near miss or deflection; although the venom an adult coral snake holds is enough to kill up to five adults, it cannot release all its venom in a single bite. Historically, however, the mortality rate was estimated to be about 10–20%, with death occurring in as little as one to two hours, or as much as 26 hours after the bite. This is not that surprising, since the LD100 for humans is estimated to be 4–5 mg of dried venom, while the average venom yield is 2–6 mg with a maximum of more than 12 mg. This is probably why current standard hospital procedure in the U.S. is to start with antivenin therapy for coral snake bites, even if no symptoms are found yet. Wyeth discontinued the manufacture of coral snake antivenin in 2010, citing a lack of profitability. Pfizer has also decided to halt production of its antivenin for similar reasons.
