The Graboid is a fictional species of sandworm that acts as the main antagonist of the Tremors franchise. The creature made its debut in the 1990 film Tremors (although the name "Graboid" was only mentioned briefly), and reappeared in its five sequels.
The Graboid was named by Walter Chang (Victor Wong), a store owner who later gets eaten by one in his own store. The only other person in the first film to use the term "Graboid" is Val McKee (Kevin Bacon). In the second movie Earl Bassett (Fred Ward) recalls the name "Graboid". The creature is similar to the legendary Mongolian death worm. According to UGO.com, "Graboids are to the desert what sharks are to the ocean".
Graboids advance through several radically different life cycle stages.
1.1.2 El Blanco
1.1.3 The Queen Bitch
1.1.5 The Big Boy
2.2 Hunting and intelligence
3.2 Hunting and intelligence
4 Dirt Dragon
5 Life cycle
7 Hypothetical taxonomy
8 Film appearances
8.1 Tremors (1990)
8.2 Tremors 2: Aftershocks (1996)
8.3 Tremors 3: Back to Perfection (2001)
8.4 Tremors 4: The Legend Begins (2004)
8.5 Tremors 5: Bloodlines (2015)
First introduced in the 1990 film Tremors, Graboids are depicted as subterranean animals, superficially resembling gigantic worms or grubs, with long cylindrical bodies. When fully grown, a Graboid will be up to 30 feet (9.1 m) long, and 6 feet (1.8 m) across at the widest point, and weigh 10–20 tons. Graboids have no eyes; they do not need them, due to living underground. Their heads consist of a massive black armored beak, which is used to push aside the dirt while digging. The beak opens like a grotesque flower; it consists of a wide upper jaw, a thinner lower jaw, and a pair of hooked mandibles, one on each side. In Tremors 5: Bloodlines, they are reported to have a semi-rigid internal structure, such as that the cuttlebone of cuttlefish.
Graboids have three long powerful snake-like tentacles, which are prehensile and can have at least a good 6 foot (1.8 m) reach; possibly up to 10 feet (3.0 m) or greater. Each of these tentacles (which have been loosely compared to functioning like the creature's tongue) terminates in a toothed mouth of its own. It is unclear if they bite off and swallow food on their own, or if they are simply used to get a better grip on prey so it can be dragged into the creature's jaws. Normally kept retracted in the Graboid's throat, these tentacles were initially mistaken for the whole creatures, causing the characters in the first Tremors film to underestimate the size of their underground opponents. The Graboid's common name is derived from these prehensile tentacles, which 'grab' prey and pull it back down the Graboid's hungry gullet. At times, these tentacles appear to be semi-autonomous, hissing and writhing like snakes. Food is typically swallowed whole, though early in the first film, they are shown to be capable of dismembering and decapitating prey.
A Graboid's hide is thick and leathery, with a rough, pebbly texture that gives them a reptilian appearance (although they are not reptiles). This makes them very hard to kill with anything short of saturation bombing or large-bore rounds. Graboids are immensely strong, able to topple over mobile homes, tow heavy objects such as a pickup truck without slowing down, smash through brick walls, and pull a station wagon underground. Encircling their bodies are short spikes that all move in unison to push the Graboid through the dirt, similar to the setae of an earthworm. They can burrow faster than a human can run; a Graboid in Tremors 3: Back to Perfection could keep pace with Burt's truck. With armored head and mobile spikes working together in unison, a Graboid can "swim" through loose soil at high speeds, but they cannot tunnel through solid rock. So in the first movie, there was a Graboid who rushed to a stone and died. Graboids (and their imago forms, the Shriekers and Ass-Blasters) have distinctive orange blood. Graboids also have a powerful stench, which is evident several times throughout the first film. Though underplayed in the second and third films, the Graboid's stench becomes a critical plot point in Tremors 4; Juan can identify the Graboids as being the unseen killers in the silver mines later in the film due to them sharing the same vile odor.
In the original film, a Graboid dubbed "Stumpy" by Val and Earl showed to be very intelligent (when it swallowed a bomb, it spit it out again) and very patient in waiting for its meal. It got its name for one of its dismembered tentacles which got stuck in Val and Earl's truck as they drove away after having been caught by it. It still used this tentacle to its best ability. Stumpy was later left as the last of the four Graboids in the film and eventually tricked by Val into falling down a cliff-wall to its demise.
Tremors 3 introduced a sterile white/albino Graboid dubbed "El Blanco", which is thus unable to reproduce and happened to prey upon other Graboids, Shriekers and Ass-Blasters. El Blanco ate one of its own kind, an Ass-Blaster, at the end of the film, saving Burt Gummer and his two companions. This Graboid was eventually left alive (with Burt getting to know and actually like this Graboid) while other non-sterile Graboids were allowed to be hunted and killed. With the preservation of this Graboid, the valley and town of Perfection became a protected area under the Endangered Species Act. During Tremors: The Series, the residents of Perfection have adapted to living side-by-side with El Blanco and protect him from threats at times. In return, it often indirectly aids them in certain situations, if only by circumstance at times. In Tremors 5: Bloodlines, it is unknown if El Blanco is dead or very old, surviving in Perfection.
The Queen Bitch
The Queen Bitch is the leader of a nest of Graboids and Ass-Blasters in Tremors 5. She is of a different, more evolved breed that is only seen in Africa. During the movie, she protects a nest with several Ass-Blasters and another Graboid in hopes of propagating their species through the dozens of eggs in their nest. The nest is discovered by poachers, one of whom tricks Burt into going to Africa in order to capture a live Ass-Blaster. The Queen Bitch, as Burt dubs her, acts as the nest's main line of defense, attacking anything that gets close while the other Ass-Blasters begin targeting a nearby village and reserve to keep their eggs safe. After a poacher is chased near the nest by her sentient tentacles, the Queen Bitch reveals herself emerging from the ground, flying high in the air and swallowing the poacher whole. After Dan Bravers arrives in his helicopter to pick up Burt and Travis, the Queen Bitch uses her grabbers to kill his co-pilot and drags Dan out of the helicopter personally. However, Dan unloads a shotgun into her stomach, causing her to spit him out. Following the destruction of the nest by Burt with the helicopter's rocket pods, the Queen Bitch travels to the nearby village where a little girl has the last egg, intending on retrieving it to preserve its bloodline. The Queen Bitch confronts the villagers who draw her into a trap where a lightning strike forces her to the surface. As Burt, Nandi and Baruti fire upon her, the Queen Bitch receives a direct lightning strike down her gullet, killing her and causing her to explode.
Sally is the name given to an Arctic Graboid appearing in Tremors: A Cold Day in Hell by Swackhammer. According to Swackhammer, he named the Graboid after his ex Sally Soulsmasher: "she was a dirty man-eating bitch who used to stick her nose where it didn't belong." During the Arctic outbreak, Sally attacks the research station along with the Big Boy, but is kept out of the hanger by a makeshift electrified fence extending into the ground. After some nearby DARPA agents make too much noise, Sally attacks them before the drill activating draws her back again. To buy time to stop the drill, everyone in the hanger begins using power tools to make a massive amount of noise, drawing Sally back towards the hanger. Just before she arrives, Swackhammer reactivates the electrified fence at double the power. Sally runs into the electrical current and explodes causing Burt to quip "Broke into the wrong goddamn hanger, didn't you ya bastard?!" However, killing her shorts out the generator for the fence.
The Big Boy
The Big Boy is the nickname given to an Arctic Graboid in Tremors: A Cold Day in Hell by Travis Welker. Following the death of the local Ass Blasters and two other Graboids, the Big Boy is the only Graboid left in the area and has to be captured alive in order to extract antibodies to save Burt Gummer's life from a parasitical infection he picked up from being swallowed by a Graboid in Tremors 3. Working together, Travis and the scientists at an Arctic research facility devise a trap for the Big Boy, trapping the Graboid in a storage container with bars positioned to keep its maw open. During a brief fight, a weakened Burt manages to damage its tentacles with an HK-91, allowing Travis to crawl into the Graboid's mouth and draw fluid from a sack in the back of its throat which proves sufficient to cure Burt. During the movie, Travis makes a deal with a DARPA agent to turn the Big Boy over to them if they will give Burt the deed to his property and a permanent immunity from taxes. Once the deal is completed, Burt flies an RC plane loaded with explosives into the Big Boy's mouth and blows the Graboid up, keeping it out of the hands of DARPA who express an interest in turning the Graboid into a bioweapon.
Graboids are shown to be ravenous carnivores, always on the hunt for food. Indiscriminate eaters, their diet includes sheep, cattle, horses, donkeys, coyotes, and humans. They are known to be cannibalistic when the opportunity presents itself; the sterile albino Graboid dubbed "El Blanco" consumed an Ass-Blaster in Tremors 3. Lacking eyes or a nose, they are shown to hunt by sensing seismic vibrations which are produced by sounds and movements (such as walking). Because they are unable to tell the difference between edible and inedible vibration sources they adopt a policy of "eat first, ask questions later", swallowing whatever sets off their vibration sensors and regurgitating anything that is inedible. Inedible objects can be spat out with considerable force, being propelled high into the air. Due to the sensitive hearing they use for underground navigation, Graboids are so sensitive to sound they must retreat from loud explosions, which cause them great pain.
Graboids are ambush predators, preferring to sneak up on their quarry, though they are shown to chase it down with great determination. They erupt from the ground and use their tentacles to ensnare prey, pulling them into their mouth (sometimes only the tentacles break the surface). The tentacles wrap around the prey, biting into its flesh or hooking the prey with their horn-like spikes. When prey attempts to flee by climbing (for instance onto the roof of a house or car), Graboids will dig away the earth under the hiding place, undermining it until it collapses or sinks low enough to allow the Graboid to pluck off the prey. When they are unable to break down the prey's hiding spot, the undaunted Graboids will continue circling it, like sharks at sea, until it ceases making vibrations. Usually they wait so long the prey dies of dehydration or starvation, i.e. several days.
Graboids are depicted as highly intelligent, possessing memory and the ability to learn. For instance, in the first Tremors film the characters successfully killed a Graboid by having it swallow homemade dynamite. The second Graboid (nicknamed "Stumpy" by Val) had apparently noticed this trap and simply regurgitated the dynamite. Other examples are when the characters escaped on a bulldozer which was too big to be toppled (weighing 30 tons) or undermined (it could drive away before the Graboids had a chance to dig away enough of the dirt under it), the creatures dug a trap in its path.
The second stage of the Graboid life cycle is the Shrieker, first seen in Tremors 2. Unlike their previous incarnations, the huge, subterranean and limbless Graboids, Shriekers live on the surface. Much smaller than Graboids, Shriekers are about 5 feet (1.50 m) long and 4 feet (1.20 m) tall. While Graboids are worm-like in shape, Shriekers slightly resemble dinosaurs or heavy ground-dwelling birds, having stout, three-toed legs (but no arms) and a compact body. They also have a short, stump-like tail. This tail, as well as some small bulges in the neck, has some orange coloring on it. Its function is not mentioned.
Shriekers gestate within a Graboid, and after a sufficient amount of time, will tear their way out of the Graboid they were in, killing it in the process. This somewhat resembles how parasitic wasp larvae will tear out of a caterpillar, though Graboids and shriekers are both different life-stages of the same species. A Graboid can sense when this time is coming near, and in anticipation will instinctively lie in one place above ground until the Shriekers hatch out of it. In Tremors 2, the Graboids appeared to spawn three Shriekers per worm. However, in Tremors 3, Burt discovers that one Graboid can spawn 6 from itself. It is likely that the exact number varies, somewhat like the number of pups in a dog's litter. Exactly how this is achieved isn't clear: Graboids do not "give birth" to Shriekers like a medusa-form alternating with Shriekers reproducing and giving birth to Graboids; the Shriekers simply tear their way out of Graboids. Graboid embryos actually form in clusters, only one of which then matures into an "adult" Graboid, while the embryos of its siblings are distributed within its body. These embryos continue to grow as essentially parasitic twins, "gestating" within their Graboid sibling, until they reach a mature size and crudely tear their way out of the Graboid.
The one thing that shows Shriekers are related to Graboids is their skull. Just like a Graboid's, it consists of a powerful, beak-like armored upper jaw and a much narrower lower jaw surrounded by two mandibles. Both the jaws and the mandibles have sharp hooks and serrations to hold on to prey. The beak is very powerful; Shriekers are capable of ripping through sheet metal with ease. While Graboids have three prehensile tentacles for tongues, complete with jaws, Shriekers have more normal tongues: singular ones lacking jaws. Like a Graboid's, the tongue is relatively stiff (for a tongue.) It can be stretched out approximately 3 feet (90 cm) and has some short bristles on it, not unlike the tongue of a cat.
The Shriekers' most notable feature is their heat sensor, a brain-like pulsating organ atop their head which is usually covered by a frill-like flap of skin, which is supported by a small ridge at the base of the skull. Using this sensor, Shriekers sense infrared heat, which is their only sense other than taste and touch as they lack eyes, ears or a nose. As shown by shots in Tremors 2 depicting the creatures' point of view, the heat sensed by the Shriekers is apparently processed into an image highly similar to that of an infrared camera. Another thing unexplained in the films is the Shriekers' ability to "see" heat before raising the frill covering their heat sensor; they always seem to know when to raise it. It is explained on the Stampede Entertainment FAQ that they can see some heat through the frills. Raising them merely enables them to make full use of the obviously delicate sensory organ, similar to opening one's eyes widely. Individual Shriekers are much easier to kill than Graboids, being smaller, surface-dwelling and more easily damaged by firearms; but conversely, they hunt in groups and rely on swarm tactics. Like Graboids, Shriekers have malodorous orange blood.
While individual Shriekers are not as large as a single Graboid, the main advantage of Shriekers is that they can very quickly reproduce asexually, increasing their numbers exponentially in a matter of hours. After one Shrieker eats a sufficient amount of food, perhaps as little as one or two meals, it will vomit up a miniature new Shrieker, about 10 inches tall, which will rapidly grow into a full-sized Shrieker. One Shrieker can produce multiple new Shriekers in this fashion (without harming itself, as the Graboid-to-Shrieker transformation does) and each new Shrieker will in turn produce new Shriekers, as long as there is sufficient food. Apparently they can metabolize food very efficiently. In Tremors 2, a single Shrieker which gained access to a large stockpile of MRE's was able to give rise to dozens of new Shriekers within a few hours, as each new generation of Shrieker reproduced. In Tremors 3, the six Shriekers were able to spawn an entire herd in under 12 hours.
Exactly how they are able to reproduce asexually is not clear, but the faux scientific documentation on the SciFi Channel website theorized that this is related to how one Graboid contains multiple Shrieker embryos: fertilized embryos will clump together, only one of which turns into a Graboid, but only 3-6 of the dozens to hundreds of embryos in the cluster will actually turn into Shriekers that hatch from the Graboid. The rest lie dormant within the adult Shrieker, but rapidly grow when it has consumed enough food to gestate one or more of the embryos. It is not clear why new Shriekers have to kill the Graboid they gestate out of, while Shriekers produced from other Shriekers do not. It could be possible that the dead Graboid potentially would be food for the emerging Shriekers, so that they could gestate the rest of the embryos.
Hunting and intelligence
Unlike the solitary Graboids, Shriekers are pack hunters, using their numbers to bring down large prey. Sensing heat, they let out loud screams (earning their name). While the sound is useless (as they are deaf) they produce a lot of heat when screaming, alerting each other to the presence of prey. When hunting, Shriekers show some good feats of insight and cooperation, using each other to form natural ladders to reach prey hiding on high ground such as rooftops, although as shown in the second film, if they do not find prey or if they are blocked off from access, Shriekers will simply stand motionless, occasionally making a sound resembling a cross between vomiting and barking.
A weakness to the Shriekers' heat sense is the use of a fire extinguisher to temporarily cloak a person from both Shriekers and Ass-Blasters. This method of disguise was used in both the second and third film. (Earl Basset had used it to set a large bomb in a warehouse that contained several Shriekers, and the second time when a scientist sent to study the Graboids had found one on the surface post-metamorphosis and were ambushed by the newly hatched Shriekers)
Graboids, hunting by vibrations, often attack inedible objects, and the heat-seeking Shriekers are no different. They have been observed attempting to eat warm car engines, electronic cables and steamed clothes. Shriekers also feed on cold objects which they find by dragging their tongue over the ground. They have been observed eating military rations, and could possibly also feed on plants, which would make them omnivores.
The Ass-Blaster, or Lightning Bird, is the third and final stage of the life-cycle including the Graboid and Shrieker. The 'Blaster first appears in Tremors 3 . It is named in Tremors 3 by Jodi Chang (Susan Chuang), the niece of Walter Chang who named the graboids in the first Tremors film.
After about three days, a Shrieker will metamorphose into an Ass-Blaster. This is not as drastic a process as when Shriekers hatch out of Graboids, instead involving a Shrieker molting its outer skin layers.
Also like Shriekers, Ass-Blasters have bird-like legs ending in three-toed feet, and their feet have three slender black talons. The Ass-Blasters' most striking features are their wings – they have red/pink-colored sail-like structures at the back of their bodies, consisting of a semi-translucent skin supported by rigid stems. A third dorsal sail extends from the spine down the back and tail. Ass-Blasters use these wings to glide through the air. In order to take off, they produce an explosion from their rear ends, earning them their name. This is achieved by mixing two chemicals near their colon (by shaking their hind quarters). Creature designers Tom Woodruff and Alec Gillis borrowed this design from the real life bombardier beetle. The mix explodes upon exposure to air, launching the creature into the air. The 'Blaster also learns at an extreme rate and can easily comprehend how to use its natural means of transportation as a torch, such as when one attempted to melt through a fire door in Tremors 3. They have been known to spontaneously combust when accidentally poked with sharp flaming objects.
Like the other life cycle stages, Ass-Blasters have orange blood. A dead Ass-Blaster is found to contain a Graboid egg, completing the life cycle. It is theorized that the flying ability of Ass-Blasters allows them to spread their eggs over a wider area. Ass-Blasters can live for several years, though their maximum lifespan is unknown. As they appear to be the final stage of the Graboid life-cycle, this would also make them the most stable: Graboids eventually die when the Shriekers inside of them hatch out, while Shriekers only live a few days before molting into Ass-Blasters.
The African species is notable for their beak shape and their wings that are somewhat different from the American species.
Hunting and intelligence
Ass-Blasters hunt like birds of prey, scanning the ground for prey while gliding on hot air currents. Their heat sensors are much wider than Shriekers', allowing them to view large sections of land at the same time. Judging from shots in Tremors 3 depicting the Ass-Blasters' point of view, the heat they sense is processed into an infrared-camera-like image, just as how Shriekers see the world. An Ass-Blaster's heat vision is much more detailed than a Shrieker's. Like the other creatures, Ass-Blasters are also attracted to inedible heat sources such as fires.
For reasons unexplained in the film, unlike their previous life cycle stage of Shriekers, Ass-Blasters will slip into a coma after eating too much, instead of multiplying. Like the other life-cycle stages, Ass-Blasters are intelligent, capable of learning from their mistakes. When several Ass-Blasters were blown up by being shot with burning spears fired from a makeshift potato gun in Tremors 3, one Ass-Blaster quickly learned to dodge these projectiles.
Tremors 4: The Legend Begins revealed that Graboids have a juvenile stage after they hatch, dubbed Dirt Dragons by Tecopa (August Schellenberg). They are not explicitly a fourth major life stage, but the early juvenile portion of the initial Graboid stage. They essentially resemble smaller, more compact versions of mature Graboids (leading to them also being called "baby Graboids with a typical size of about 4 feet long. The unique head shape of full-sized Graboids, with their beak and lower triple-mandible, are already present. Their tongue-tentacles are also present, but still too small to be helpful in attacking prey. In order to quickly down animals larger than themselves, Dirt Dragons are capable of physically jumping out of the ground to tackle their prey. As they mature into adult Graboids, their weight increases to the point that they can no longer jump, but by this point their mouth-tentacles have grown to full size and can be used to hunt.
Graboids are hatched from eggs laid by Ass-Blasters (the final stage in the life cycle), as indicated in Tremors 3. These eggs split open diagonally. Carbon dating has shown that the eggs can lie dormant for at least 300 years, explaining why Graboid sightings are rare and random. As shown in Tremors 4, the hatching of the eggs is prompted by warmth; in Tremors 4 hatched eggs were found in a hot spring.
· Baby Graboids (nicknamed "Dirt Dragons", and by the fan-base, "Shooters"[ are 4 feet (1.2 m) long and are much shorter and more compact in comparison to the adults, but already have the typical set of jaws and mandibles. The baby Graboids also have a row of armored scales on their backs for protection, which are shed before they fully mature. Like adults, they have large spikes used for digging; extra large rows of spikes sprout from the sides of their body. Being smaller than the adults, baby Graboids are able to hurl themselves out of the dirt to tackle prey, like "some kind of demonic trout", according to Hiram Gummer (portrayed by Michael Gross) in Tremors 4. Their tentacles are underdeveloped at this point in their lifecycle.
· Upon maturing, Graboids will resume attacking and consuming prey. After that, they will seek a secluded spot where they will metamorphose. Three to six Shriekers will emerge from their body where they have been growing in large sacs, killing the Graboid. The exact number of Shriekers that emerge could possibly depend on how well-fed the Graboid is, usually between three and six. This is shown how in Tremors 2 the Graboids metamorphosed into three Shriekers each but in Tremors 3: Back to Perfection there was six. Alternately during Tremors: The Series it was mentioned that a Graboid had created four Shriekers.
· Upon emerging, Shriekers will search for food. When they have eaten a sufficient amount of food, Shriekers will spit out a cocoon containing a mini version of themselves. This ability to reproduce asexually allows them to expand their numbers greatly over a short period of time, although it is unknown whether a Shrieker can produce more than one clone. The newborn Shrieker is fully developed, about 10 inches (25 cm) long and starts growing right after birth, as seen in Tremors 2.
· When a Shrieker is around three days old, it will undergo a molting process, turning into an Ass-Blaster. Ass-Blasters can live up to several years (an individual sold to Siegfried and Roy in Tremors 3 was still alive two years later). They attack anything warm. While shriekers reproduce asexually when they have fed enough, Ass-Blasters slip into a coma when they eat a large amount of food, as seen in Tremors 3. They can reproduce, however – each Ass-Blaster carries a Graboid egg in its gut. Because they cover large distances when flying, they can carry these eggs further away, as theorized by Jodi Chang in Tremors 3.
· The Graboid's evolutionary origins are intentionally kept very vague in the first film; the creators of the film were unconcerned with this detail, offering no explanation as to where the Graboids came from in the original film, wanting to avoid the typical clichés of the creature-film genre. The main characters even satirize this convention by attempting to guess where they came from: outer space, nuclear mutations, genetic engineering and prehistory are all offered up as possible explanations.
· The answer was revealed in Tremors 2, when a fossil Graboid spike was discovered and dated back to the Precambrian, making it at least 600 million years old; the Graboids are apparently from Earth, or have at least existed on Earth for a very long time. Strangely, no prey large enough for Graboids to eat was supposed to have evolved yet at that time; in fact, it was thought there was no life on land at all, and most of the land would have been composed of bare rocks. A write-up written by the SciFi channel for Tremors: The Series re-coined this by saying the fossil was incorrectly dated and actually from the Devonian period. By that time, prey big enough for Graboids to eat had evolved (amphibians), though they do not rule out a possible extraterrestrial origin.
Promotional material once hosted on the Sci-Fi Channel website gave them binomial names: Caederus americana (Graboid), C. mexicana (Shrieker), C. mexicana combustus (Ass-Blaster). It put them in the Sepioida order in the cephalopod class of mollusks, in a fictional family called Vermiformidae.
Three varieties of Graboid are shown in the films. This number can be expanded to as many as four (juvenile Dirt Dragons as larvae, "adult" Graboids as pupae, Shriekers as sub-imagos, and Ass-Blasters as imagos) or reduced to as few as two (Dirt Dragons as larvae and Ass-Blasters as adults; similar to the sharp lexical division of amphibian metamorphosis into tadpole and frog/newt). Their division into three forms seems to be based on habitat or locomotion: subterranean Graboids, terrestrial/cursorial Shriekers, and aerial Ass-Blasters.
The standard Graboid, introduced in Tremors and seen in the first four films, is a subterranean animal, resembling a gigantic worm or grub, with a serpentine body, four massive, black, armored beaks on its head, and no eyes. Instead of hunting visually the Graboids find their food by sound; they are also able to sense ultrasonic signals as demonstrated in Tremors 3. It also has several spikes on its sides that it uses to push itself along underground. The full adult form is about thirty feet long. Graboids have a trio of long, powerful, snake-like tentacles, which are prehensile and have a reach of at least ten feet. Each of the three tentacles has a small, tooth-filled mouth and two horns. They often seem to have minds of their own. They die as soon as the Graboid they belong to does.
Tremors 2: Aftershocks (1996)
In Tremors 2: Aftershocks, "Shriekers" are introduced. Fully grown Graboids die while giving birth to a random number of creatures depending on the amount of food they consumed, between three and six; these creatures are the Shriekers. Much smaller than Graboids, about 6 feet (1.8 m) long and 4 feet (1.2 m) high,, Shriekers live above ground and resemble a small dinosaur or heavy ground-dwelling bird, with stout, three-toed legs and a compact body. They have similar beaks on their heads, but lack the tentacles of a Graboid and instead have a single, long tongue, and like Graboids lack eyes and noses, but also don't have ears. Shriekers find prey through a retractable heat-seeking crest on the top of their heads, as well as their tongues which they use to find cold food through taste. They are hermaphroditic and will gag up small Shriekers as long as they find food.
Tremors 3: Back to Perfection (2001)
The third stage, the "Ass-Blaster", is introduced in Tremors 3: Back to Perfection. Shriekers turn into Ass-Blasters, which resemble their original Shrieker, shedding their skin as they grow and change. They are capable of gliding with the use of red/pink-colored sail-like structures at the sides of their bodies, consisting of a semi-translucent skin supported by rigid stems and a third dorsal sail that extends from the spine down the back and tail. In order to take flight, they shake and quiver their tails and backsides and seem to be mixing two liquids which produce an explosion of flames from their rear end, similar to a Bombardier beetle's blast of acid. Ass-Blasters fall into a "food coma" when eating too much and carry Graboid eggs within their bodies, supposedly bringing the life cycle full-circle.
Tremors 4: The Legend Begins (2004)
Introduced in Tremors 4: The Legend Begins, the juvenile form of the Graboid is about two feet long and looks somewhat similar to the adult form. The younger Graboid has a proper beak (without the three separate jaws that form the lower part of the beak) and lacks the trio of serpentine tentacle tongues. Also, since they are not strong enough to pull a victim underneath the dirt, they instead propel themselves out of the dirt with extreme speed to take down a moving target. These young Graboids are seen in the film wherein the characters refer to both juvenile and adult Graboids as "Dirt Dragons". Graboids are also intelligent and learn very quickly. For instance, in the first film, when two Graboids discover that the bulldozer is too heavy to lift, they simply dig a trap in its path.
Tremors 5: Bloodlines (2015)
A newer, bigger, meaner species of Graboid appears in Africa. In the film, Burt indicates that the African version of the species is larger and more dangerous than the previously encountered variety. They are able to dig through the dirt much faster, even capable of "breaching" the surface and leaping onto their prey from above. Additionally, the prehensile tentacles, or "grabbers", are capable of disconnecting from the main body and acting independently. It is unknown if this species has a Shrieker phase, as none are observed in the film and Burt questions their absence. One of the paleontologists in the film speculates that this variety of Graboid is capable of chewing through rock by emitting an acid-like substance from its mouth, therefore rendering the previously safe refuge of large desert boulders obsolete.
The Ass-Blasters that spawn from this variant are likewise larger and deadlier than the Perfection Valley kind. Their build is stockier and bulkier, and the chemical reaction that allows them to take off appears to be more violent. The wings are larger and more bat-like, and the tail is longer and more defined. They are also notable for their strange beak shape, somewhat different from the American species. They are shown to be strong enough to pick up a fully-grown man with their feet, which now have two front-facing toes and two smaller rear-facing ones, and carry him a relatively long distance. Their mandibles are less defined, with a vortex of tooth-lined jaws behind them.