For decades now, UFO stories have mostly involved blurry lights in the sky, shaky footage shot on potato phones and men called Del insisting they’d seen something strange from their truck on the drive back from a night spent at their local dive bar.

Slowly but surely, however, the idea of extraterrestrial life visiting Earth has started to become a tad more serious.

Now a former CIA scientist has claimed that the US government secretly knows about at least four different types of alien life linked to crashed UFOs.

Dr. Hal Puthoff, who worked on intelligence projects involving UFO research and psychic spying during the 1970s and 1980s, made the claims recently during an appearance on Steven Bartlett’s Diary of a CEO podcast.

The four species he referred to have also been discussed by the physicist Dr. Eric Davis, another figure who’s been linked to plenty of top secret Pentagon projects and UFO investigations down the years.

Last year, Davis told members of Congress that witnesses had described ‘Grays, Nordics, Insectoids and Reptilians’ as the possible operators of mysterious craft recovered by the US.

The Grays are, of course, the classic alien look. Small. Grey. Giant black eyes. Massive heads. The sort of thing that’s been appearing in low-budget documentaries on rubbish TV channels for decades. X Files stuff.

Their popularity exploded after the famous Betty and Barney Hill case in the 1960s. The American couple claimed they’d been abducted by strange humanoids with smooth grey skin and oversized almond-shaped eyes.

Then there are the Nordics, who – apparently – look like extremely tall Scandinavian humans with blond hair, blue eyes and fair skin.

Stories about them have floated around UFO culture since the 1950s, with some believers linking them to the Pleiades star cluster, around 440 light years from Earth. They’re said to be highly evolved and benevolent in nature.

The Insectoids are quite a bit less appealing, we’re afraid.

People who claim to have encountered this type of alien describe giant mantis-like creatures with antennae, mandibles, exoskeletons and multiple limbs. Some stories even claim they communicate telepathically, which sounds stressful enough before you factor in their giant bug faces.

Insect-like alien beings have been turning up in science fiction and UFO mythology for well over a century, including in Georges Méliès’ early cinematic classic A Trip to the Moon from 1902.

Read More: CIA scientist claims crashed UFOs contained four different alien species