The Lyre Snake – just mildly venomous

The Lyre snake is named for a V-shaped marking on the back of the head. This marking is often more prominent on females. Dark brown saddles occur on a light brown to light gray back. The underside is creamy-white or yellow with scattered brown spots. At first glance the Lyre snake may look like the common king snake. But, the Lyre snake’s neck is narrow, making the head appear more triangular, similar to other venomous snakes. Also, the eyes have pupils that are vertical slits rather than round as are on non-venomous snakes. Lyre snakes can get up to four feet long.

The Lyre snake (Trimorphodon lambda) is usually a nocturnal hunter, but can be found basking in the sun in the spring and fall. The main prey are lizards and mice, but the snake also goes after other prey including birds (It does climb trees).

The range of this snake includes most of Southern Arizona, and extends to southern Nevada and Utah, as well as northern Mexico. It favors the lower rocky canyons and arroyos of hills and mountains from sea level to 7400 feet (2300 m). A rock dweller, it wedges itself in the many crevices and fissures that are abundant in rocky areas. This snake is an occasional resident of flat lands, according to the Arizona-Sonora Desert Museum.

According to the Tucson Herpetological Society:

Lyre snakes are not usually dangerous to humans. “When threatened, the Sonoran Lyresnake will often rattle its tail. It will sometimes raise the anterior portion of the body, and strike and bite if further provoked.” The Lyre snake does not have fangs. Rather, “Toxins produced in a Duvernoy’s gland are delivered to prey and attackers via elongated, grooved teeth in the rear of the upper jaw. A large individual is capable of delivering a venomous bite to a person. Symptoms range from none to local redness, itching, swelling, and numbness, particularly if the snake is allowed to chew.”


For more photos and a very detailed description, see an article from the Tucson Herpetological Society: .

More snake articles:

Arizona Coral Snakes – pretty and very venomous

The Coachwhip a colorful snake

Gopher snakes

Kingsnakes versus Rattlesnakes

Mexican vine snakes


Speckled Rattlesnakes


Don’t Touch Buckmoth Caterpillars

Buckmoths (genus Hemileuca, several species) are found across southern Arizona, New Mexico, and Texas, and south through Sonora and Chihuahua, Mexico. Habitat varies from mesquite bosques to grasslands and plains, depending on the species. They feed on the leaves of palo verdes, mesquites, and other desert trees. The spines of the caterpillars can release a very painful toxin, so don’t touch them.

The following material is from a publication of the Arizona-Sonora Desert Museum which was derived from: Tread Lightly: Venomous and Poisonous Animals of the Southwest, by Rich and Margie Wagner. Rio Nuevo Publishers, Tucson, AZ. 2005. Reprinted with permission of ASDM.

Physical Characteristics

A number of caterpillars have developed an effective form of chemical defense that utilizes “stinging spines” on their bodies to ward off would-be predators. The most common of these are the buckmoth caterpillars, of which about 23 species are found in the Southwest. The full-grown caterpillars are about 2 inches long (5 cm) and are covered from one end to the other with bristles or urticating spines. The colors are variable and depend on the species. The fast-flying adult moths have a wingspan of about 2-3 inches (5-7.5 cm), and vary in color from relatively nondescript tan and brown to brilliantly colored yellow and orange on black. They are primarily day-fliers, and they do not have stinging spines. (Urticating: cause a stinging pain or sensation)


Juno Buckmoth (Hemileuca juno) caterpillars feed on the leaves of common desert trees, often in groups. When molested, the caterpillar usually stops feeding and remains motionless, counting on camouflage and the urticating spines for protection. Caterpillars occasionally drop off branches and land on people, or are brushed against by riders on horseback, resulting in envenomation by the urticating spines. Other buckmoth caterpillars, like those of the range caterpillar moth (Hemileuca oliviae), feed on grasses, and envenomations can inadvertently occur when a person is walking through the grass.


The life cycle of moths is somewhat complex, and the particular details are species-specific. Flights generally occur from September through December. The mating of most Hemileuca moths, such as the Juno or mesquite buckmoth, begins shortly after sunset on fall evenings. Males use their well-developed antennae to track and follow the pheromone trail given off by female moths. After mating, the female deposits eggs on branches in host trees, with the eggs usually laid in circles around small branches. The eggs over-winter and hatch in April or May into small larvae, or caterpillars, that eat and grow for about a month, molting through five instars before they migrate to the ground and form a pupa, or cocoon, in leaf litter. After metamorphosis, most of the cocoons will hatch into adults (in the fall again), although some Hemileuca cocoons have been known to lie dormant for four years.

Effects of venom

The spines of stinging caterpillars contain toxins that are produced in gland cells. Caterpillars do not have a stinging apparatus per se, but rather depend on intentional or inadvertent contact of the spines with the skin of a victim. After the spines penetrate the skin, they break off, releasing toxins that cause mild to severe pain and other compounds that induce an inflammatory dermatitis called erucism. Because the protein components of the toxins are considered “foreign” to the body, an allergic reaction may also occur. While hospitalization is rarely required for stings on the skin, spines that enter the eyes may cause potentially serious complications.

First Aid and Medical Treatment

Anyone attempting to remove a stinging caterpillar should be careful not to incur additional stings on the hands or elsewhere, particularly as the caterpillar drops off. Wash the area immediately with soap and water. Spines that remain in the skin can often be removed with adhesive tape. Baking soda applied as a paste with water may help decrease the pain, as may ice applied to the injured area. Acetaminophen or ibuprofen may be taken for pain. Benadryl® may help treat localized allergic reactions. As always, victims with severe allergic reactions should seek immediate medical attention, as should anyone with persistent symptoms or signs of infection.

The moths, themselves, are harmless.

Buckmoth caterpillars are especially abundant in New Orleans and tend to fall out of oak trees onto unwary people. (See video about “the attack of the buckmoth caterpillars”) There are several other stinging caterpillars; see this from the Florida Poison Information Center.

See also:


Black Widow Spiders

Black widow spiders (Latrodectus hesperus) are normally shy and sedentary, but will react if they feel threatened. According to some authorities, their venom is 15 times more potent than rattlesnake venom. But black widows bites are fatal less than one percent of the time because their small fangs can’t penetrate the skin very deeply and often the spider does not inject venom. Only the bite of the female is potentially dangerous to humans.

Black widowThe female black widow has a body length up to three-quarters of an inch. She is shiny black to dark brown and has a red, hour-glass mark on the bottom of the abdomen. The male is half that size, usually medium brown with cream-colored makings on legs and abdomen.

According to the Arizona-Sonora Desert Museum:

Different species of Latrodectus are found throughout most of North America, more commonly in warmer climates. Black widows are common around man-made structures such as garages, lawn furniture, and woodpiles. They also live in a variety of natural habitats.

The black widow preys mainly upon insects that it traps in the web. The web is irregular and strong to the touch in comparison to other webs. Some species of spider wasps prey upon black widows. Black widows are shy, sedentary, and largely nocturnal. They are not aggressive, but will bite in self-defense.

The female mates only once in her lifetime, retaining sperm for future egg-laying. The smaller male is sometimes eaten by the female following mating, hence the name “widow.” This characteristic, however, is not limited to black widows, but can occur after mating in many arachnids, most of which are highly predatory. The female lays approximately 300 eggs at one time and encases them in a round, cream-colored egg sac made of her silk. One spider produces several sacs within its one- to two-year lifespan, but only one sac at a time. The spiderlings disperse by ballooning.

The black widow is one of two species within our region that is potentially dangerous to humans (the brown spider is the other). The bite can kill a human, but this is rare. More often, the bite is painful and causes serious reactions, including nausea, dizziness and abdominal cramps.

The silk of the black widow and some orb-weaving spiders is the strongest among spiders and stronger than steel wire of the same weight. ASDM notes: “A spider may have up to six types of silk glands, each producing a different kind of silk. It is actually a complex strand of proteins that is produced as a liquid, and solidifies under tension. Silk is used to build webs, catch food, line burrows, protect eggs, detect prey (as trip lines), and even to aid in dispersal.” Spiders avoid being caught in their own webs by having oil on their legs.

Black widows and other spiders prey mostly upon insects that get trapped in their web. The venom serves to paralyze and liquify the prey, so the spider can suck out the insides. Black widows are preyed upon by wasps and lizards.

Most spiders have up to eight eyes, but only the jumping spiders rely on sight to hunt. Most spiders have hairs on their bodies, especially their legs. These hairs allow the spider to feel and “hear” by displacement of air around the hairs.

See also:

A green lynx spider may be lurking in your yard

Cochineal the Little Red Bug

Desert Bees and Africanized Bees

Life on a dead saguaro

New giant tarantula found in Sri Lanka – Video

New scorpion species found in Santa Catalina Mountains near Tucson

Scorpions, Vinegaroons, and Sun Spiders

Tarantula Hawks Deliver The Big Sting

Venomous Centipedes and Cyanide-Oozing Millipedes

Who’s Afraid of Tarantulas?

The Psychedelic and Toxic Sonoran Desert Toad

The Sonoran Desert toad (Bufo alvarius), formerly known as the Colorado River toad, is one of the largest native toads of North America; they can get up to 7 inches long.  The toad is greenish-gray on top and creamy or white on the bottom.  They have large white “warts” at the jaw angle, large parotid glands and a few large lumps on the hind legs.  Toadlets are tan to green with orange or red spots.


This toad ranges from Central Arizona to southwestern New Mexico and Sinaloa, Mexico.  It used to occur in southeastern California but has not been reported there for about 40 years.  The Sonoran Desert toad inhabits creosote bush desert scrub, grasslands up into oak-pine woodlands, and thornscrub and tropical deciduous forest in Mexico.  This time of year you might see one in your yard.  These toads can climb fences if there is enough purchase.

According to the Arizona-Sonora Desert Museum: “Sonoran Desert toads feed upon a variety of insects throughout their lives. Adults eat primarily beetles, although large individuals will occasionally eat small vertebrates including other toads. Sonoran Desert toads are active from late May to September, though principally during the summer rainy season. They are nocturnal during the hot summer months. The male’s call is weak, sounding somewhat like a ferryboat whistle. Eggs are laid in temporary rain pools and permanent ponds. Larvae metamorphose after 6 to 10 weeks. This species lives at least 10 years, and perhaps as many as 20 years.”

A defensive milky neurotoxin venom can be released from the parotid gland behind the eyes and similar organs on the legs.   The venom is potent enough to kill a large dog, should the dog grab a toad.  Symptoms of envenomation include foaming at the mouth, drunken gait, confusion, vomiting, diarrhea, or complete collapse.  There is no antitoxin.

The venom can have a psychedelic effect because it contains chemicals in the dimethylethanamine family and is closely related to DMT, a naturally occurring hallucinogenic drug akin to synthetically made LSD. Toad venom has long been used by native peoples of the Colorado River region in some religious ceremonies. Some people lick the toads to get high and there are many websites explaining how to extract the venom, dry it and smoke it.  This is very dangerous because an overdose can cause cardiac arrest in humans.

By the way, what is the difference between toads and frogs?  All toads are frogs, but not all frogs are toads.  According to, in general, frogs have two bulging eyes, strong, long, webbed hind feet that are adapted for leaping and swimming, smooth or slimy skin, tend to like moister environments, and lay eggs in clusters.  Toads have stubby bodies with short hind legs, warty and dry skin, parotid glands behind the eyes, and tend to lay eggs in long chains.


Venomous Centipedes and Cyanide-Oozing Millipedes

Among the creepy-crawly critters in the Sonoran Desert are centipedes and millipedes, both of which have some interesting properties.


The Giant Desert Centipede (Scolopendra heros) can grow up to 8 inches long. The body is usually yellowish-tan, and the head and tail segments are black. The common desert centipede (Scolopendra polymorpha) is 4- to 5 inches long, and brown to tan. Centipedes have a flattened, segmented body with one pair of legs per segment. If the centipede is not moving, it can be hard to distinguish the back end from the front end because both have antenna-like appendages. But, just under the head are powerful pincers (gnathopods) which can delivery a very painful pinch and venom. The venom is not harmful to humans, but don’t try to pick up a centipede.

Centipedes are fast-moving predators that feed upon any small animal they can catch, primarily insects, but they are known to take other arthropods, lizards, and also small rodents. Centipedes usually hunt at night, but may be out in the daytime during the rainy season. Female centipedes will guard their eggs until they hatch. The centipede usually prefers slightly damp micro-habitats beneath rocks or in debris such as dead saguaros. Despite the name “centipede” Scolopendra usually have 42 legs. The number of legs depends on the species.

The Desert Millipede (Orthoporus ornatus) has a cylindrical body, up to 6 inches long. Body color varies from reddish-brown to black. Millipedes have two pairs of legs per segment. They begin life with only a few segments and add segments and legs as they grow. Millipedes are quite adaptable and occur throughout the world. They prefer humid environments and are commonly seen following summer rains (their nickname is “rainworm”).


Millipedes are nocturnal and feed on living and decaying plant material, and that includes cholla, creosote bush, ocotillo, and mesquite. They also ingest soil and help play a role in soil conditioning. For defense, it usually rolls into a coil. Upon further provocation, millipedes use chemical warfare. They can secrete, and shoot up to 10 inches, a liquid which contains benzoquinones, aldehydes, hydrocyanic acid, phenols, terpenoids, nitroethylbenzenes, and other substances. This can be very irritating. However, millipedes are usually gentle; I’ve handled them without any problem. Some people keep them as pets. Millipedes don’t bite.

Both centipedes and millipedes spend most of their time underground.


There are 17 species or subspecies of rattlesnakes in Arizona and they all object to being stepped on. So watch where you walk. In my field experience as a geologist, I’ve encountered many rattlesnakes (26 on one morning), and most of the time they don’t rattle. They prefer to remain inconspicuous. See here for a list of all recognized rattlesnake species and subspecies.


Some herpetologists regard rattlesnakes as one of the most highly specialized animals on the planet. The venom, a toxic saliva, is a complex mixture of enzymes that include hemotoxins, that attack the blood and start the digestion process in tissue, and anticoagulants. The Mohave rattlesnake also carries neurotoxic venom that may cause circulatory arrest or respiratory paralysis. That said, however, fewer than 1% of people bitten in the U.S. die as a result of the bite, but many sustain tissue damage. About 20% of defensive bites are dry – no venom injected. Venom is injected via curved fangs which fold back into the snake’s mouth. Rattlesnakes seem to have spare parts to replace damaged fangs. Baby rattlesnakes are venomous and ready to go, they just can’t inject as much venom as a larger snake.

If you are bitten, the University of Arizona College of Pharmacy recommends that you get to a hospital to get antivenom and treatment for tissue damage. Don’t bring the snake; the antivenom treats all bites. Also don’t use tourniquets, that just concentrates the venom and produces more tissue damage. Don’t use ice for the same reason. Don’t cut and suck; you can’t get enough venom out to make a difference, and, if a friend does it for you, he takes a chance of envenomating himself. Do remove tight clothing, shoes, jewelry from the affected limb.

Rattlesnakes are pit vipers, which means they have heat-sensing organs located between their eyes and nose. A rattlesnake can detect the heat of a candle at 30 feet. Some researchers claim that a rattlesnake can perceive a temperature difference of as little as 0.01 degree Fahrenheit at one foot. The snakes use this heat-sensing ability in several ways. They can follow the heat trail of prey even in total darkness. They can tell if an animal is too large to be prey and thereby avoid it. And, the exothermic (cold-blooded) snake can use their temperature sensor to help find places to properly regulate body temperature.

Rattlesnakes are most active in the warmer times of year, but in Arizona, they may be out and about any time the temperature is between 70 and 90 degrees F.

Rattlesnakes are born live, rather than hatch from eggs. The babies have the first segment of the rattle, but can’t make a noise until it sheds and gets another bead on its rattle. Mother rattlesnakes care for their young at least until after the first shed. It is a myth that you can tell the age of a snake by counting the beads on the rattle. Beads are added at each shed, and the snake may shed several times a year. The rattle material is keratin, the same as your fingernails. There isn’t anything inside the rattles; the noise comes from the segments bumping against each other as the snake vibrates its tail up to 60 times per second.

Rattlesnake eyes have slit pupils like cat eyes. The gopher snake, a non-venomous constrictor, is often mistaken for a rattlesnake, but it has round pupils and lacks the triangular head of the rattlesnake.

Other snake myths. Snakes cannot dislocate their jaws. They can open their mouths very wide because they have two jaw joints on each side separated by a (quadrate) bone. Snakes also lack bony chins. Each half of the lower jaw is separated by cartilage which enables the snake to move the lower jaws independently.

Rodents are the main prey of the rattlesnake, so the snakes provide a valuable service. They also take birds, lizards, and baby rabbits and squirrels.

At the Arizona-Sonora Desert Museum, the staff capture an average of 100 rattlesnakes per year on the grounds. After capture, the snakes are marked by color-coding the tails and, more recently, by inserting a radio chip to allow tracking. The snakes are released on the far reaches of the grounds. Rattlesnakes, however, are very territorial, so many return. So, if you are at the Museum and see a rattlesnake with a multi-colored tail, you will know that particular snake is a return visitor. And no human visitors have ever been bitten by a rattlesnake at the Museum.

Venomous Lizards

The are only two venomous lizard species in the world and both live in this general region. The Gila Monster and the Mexican Beaded Lizard.

Gila Monster



The Gila monster (Heloderma suspectrum) averages 9- to 14 inches long, but can get up to 24 inches long. It ranges throughout the Sonoran Desert region below about 4,000 feet elevation. Its range included parts of Arizona, California, Nevada, New Mexico and northern Sinaloa, Mexico. It feeds on eggs of reptiles and birds, and takes small rodents, such as pack rats, and baby mammals such as rabbits and squirrels. Mating occurs in spring or early summer. Observations in the wild suggest an incubation period of 10 months, but captive lizards produce hatchlings in about 4 months. There are two subspecies of Gila monster: the reticulate Gila monster (H. suspectum suspectum) and the banded Gila monster (H. suspectum cinctum). The reticulate Gila monster lives in the southern region part of the range, while the banded Gila monster occurs primarily in the Mojave Desert. The reticulate Gila monster tends to have its lighter markings broken up by dark scales, giving it a reticulated pattern, while the banded Gila monster generally has more unbroken bands of lighter scales.

The Mexican beaded lizard (Heloderma horridum) averages 2- to 3 feet long. It ranges throughout southern Sonora. It feeds on birds, small mammals, other lizards, and eggs. It can climb trees. Little is know about mating in the wild. Captive lizards mate in August, produce eggs in October which hatch from January to March.

Both lizards have forked tongues which they use to sample the air to find prey. They are nocturnal hunters. The thick tails store fat. Both lizards are dormant during the winter, and both spend about 95% of their time underground. A young gila monster can eat the equivalent of 75% of its body weight at one meal; an adult can consume 50% of its body weight at one meal.

The venom is a neurotoxin similar to that of a coral snake. It is released from glands in the lower jaw and conducted through grooved teeth by capillary action and chewing. The lizards don’t have fangs; they just chew on you for a while, without letting go. The lizards are very tenacious. Study of the venom suggests it evolved as a defensive toxin. Bites to humans are rare. Victims have reported intense pain within five minutes of the bite and the pain may persist for several hours. Weakness, dizziness, perspiration, nausea, chills, and fever have been reported. No human deaths have been reported.

Research shows more than a dozen peptides and proteins have been isolated from the Gila monster’s venom, including hyaluronidase, serotonin, phospholipase A2, and several kallikrein-like glycoproteins responsible for the pain and edema caused by a bite. Four potentially lethal toxins have been isolated from the Gila monster’s venom, including horridum venom, which causes hemorrhage in internal organs and bulging of the eyes, and helothermine, which causes lethargy, partial paralysis of the limbs, and hypothermia in rats. However, the constituents most focused on are the bioactive peptides, including helodermin, helospectin, exendin-3, and exendin-4. Most are similar in form to vasoactive intestinal peptide (VIP), which relaxes smooth muscle and regulates water and electrolyte secretion between the small and large intestines. These bioactive peptides are able to bind to VIP receptors in many different human tissues. One of these, helodermin, has been shown to inhibit the growth of lung cancer.

Although Gila Monsters have a fearsome reputation, they are sluggish and pose little threat to humans, just don’t try to pet one or pick one up.

Myths about Gila monsters include: how the Gila monster is venomous because it lacks an anus and “all that stuff went bad in there.” Or about how “once they bite down, they can’t let go until sundown,” or “if one bites you, don’t worry, it has to turn upside down to get the venom in you.” (ASDM).

In 1952 the Gila monster became the first venomous animal in North America to be afforded legal protection; it is therefore illegal to collect, kill, or sell them in Arizona.