Stingray Stingrays were creatures that devoured everything on a planet and could travel through wormhole s to new ones . They were named " alien stingrays " by UNIT due to their superficial resemblance to the stingrays that lived in Earth ' s seas . Biology . Stingrays had a wide head with little eyes and gills , a long tail and fins down their side . They were the size of a small car , but were still capable of flight at speeds of at least 300 miles per hour . They were extreme omnivores , capable of eating meat , plants , rock or metal . Any metal they ate would be extruded into their exoskeleton , making them bullet proof , though not immune to explosives . Stingrays would also go into hibernation when cold . Their metal exoskeleton allowed them to produce large amounts of static energy when they travelled in groups , which was capable of creating wormhole s . After eating everything on the planet , the whole swarm would start to circle the planet . The sheer mass and speed of billions of individuals would rip open the fabric of space , creating a wormhole , allowing them to travel from planet to planet and continue this life cycle . Their metal exoskeleton would allow them to survive the passage . They appeared not to possess any real sentience and acted on primal instinct alone . When talking with Captain Erisa Magambo , the Tenth Doctor stated that what they do isn ' t their fault and is just their instinct . ( TV : " Planet of the Dead " ) History . Circa 2009 , the Stingrays opened a wormhole to the planet San Helios , where they ate everything within a year , leaving only barren deserts . They then began making a second wormhole with which to leave the planet . When a Tritovore ship came to the planet to trade , it ran into the swarm . In a manner similar to birds clogging the engines of a plane , the Stingrays clogged the vents of the ship , causing it to crash from ten miles in the air . At least two Stingrays were involved in the crash and were put into hibernation by the cold . After devouring San Helios and turning it into a desert , the Stingrays began generating a new wormhole to move on . The wormhole eventually opened up into Earth , accidentally pulling the 200 to San Helios . Though they saw the Stingrays from a distance , they were unable to identify what they were without the help of the Tritovore ' s probe . Later , when Christina de Souza went to retrieve the crystal nucleus from the Tritovore ship , her body heat raised the temperature just enough to revive the hibernating Stingrays . Though Christina managed to kill one with the ship ' s security grid , the second devoured the two surviving Tritovores . The Tenth Doctor was able to return the 200 just before the Stingrays made it to the wormhole and Malcolm Taylor managed to close the wormhole after them . However , three Stingrays made it through . Conventional firearms were useless against them , but UNIT ' s mounted missile launchers proved more effective . After the threat to Earth was over , the Doctor admitted to Captain Erisa Magambo that the Stingrays would simply start again and generate a new wormhole . However , the Doctor acknowledged that their actions weren ' t their fault , being instinct and stated an intention to try to " nudge " the Stingrays wormholes onto uninhabited planets where they could feast without ever harming anyone . ( TV : " Planet of the Dead " )