The Space Caterpillars are small, fuzzy creatures which inhabit trash nebulas and spacecraft graveyards. Pidge encounters a thriving colony of them after she was ejected from a corrupted wormhole in Season 2, episode 1.
The caterpillars are small aliens that live in large colonies; individuals are covered in fur that is either bright blue, pink, green, or yellow in color. Their tan underbellies are the exception, being furless and segmented, lined with eight tiny red legs. Each caterpillar has a pair of large eyes with a visible pupil white sclerae, but they are never seen blinking. The species is capable of maneuvering through areas of zero gravity and clinging to objects to avoid floating.
Caterpillars have a small mouth and the inside is never seen. On either side of their mouths is a pair of triangular markings, curving upward and outward, that appears to glow in light blue. These markings increase in luminescence for communication, flashing as an alerting signal. The species seems somewhat understanding of common speech, as they understood Pidge when she mentioned "friends". They inhabit the dark insides of ships and clusters of debris. It's unknown what they eat, but it could be dust and gas that's trapped in the nebula.
Their markings are located underneath their eyes and in the dark, they glow to create the appearance of a large, angry creature. This is a self-defence mechanism which can be made even more effective when a large group of space caterpillars cluster together, creating the effect of an even larger, more threatening creature. The colony Pidge encounters seems to be two or three dozen strong. Coincidentally, the sickle-shaped markings resemble inverted Altean markings.
Despite this, space caterpillars are social, docile and surprisingly intelligent for their size. They demonstrate the capacity to understand human speech: when Pidge discusses her missing team, the caterpillars form a group of five. This shows that not only can they understand English, they can also comprehend that 'team' infers intimacy. They can also distinguish between inactive and active machines, sensing that the Green Lion is recharged before Pidge does, and helping her to build a satellite.
- Pidge appears to have taken some space caterpillars back to the Castle of Lions, as three of them can be seen hovering in a pile of debris in her bedroom. She has a blue one, a green one, and a yellow one that she takes to Earth when the Castle of Lions is destroyed.
- The species may have the ability to detect technological energy or Quintessence, as they noticed the Green Lion reawakened before Pidge realized.