From Lexicanum

Squigs (short for "squiggly beasts") are the simplest form of Orkoid life. There are many types of squig, each generally filling some functionary role in the Ork ecosystem. They serve as the Orks' primary food source. There are many types of squigs, but each can be generalized into a single variety, such as edible, musical, hair, medical, parasite-hunting, face-eaters, pet, buzzing and paint squigs. Some, like the face-eater types, are little more than snapping, fanged mouths on legs.¹

Squigs naturally grow and breed within the cesspits of Ork settlements, subsisting on Ork refuse. Tending the squigs are the orkoids known as Snotlings.

Current lore holds that Squigs were bred by the lost race of Brainboyz. However, Squigs were originally introduced as a Tyranid unit, and said to be of Ork origin.^2,3 Regardless, Squigs are a vital part of Ork culture.

Squig Eatin'

All squigs are edible, but some squigs are specifically bred as a food source. Gretchin are responsible for cooking the squigs, though Orks will eat raw squig if a cook cannot be found. The rarest form of these are referred to as Juicy Squigs and require a special Gretchin cook. Orks reserve the eating of Face-Eating squigs for special contests.⁴

Breeds of Squig

• Eatin' Squig - Edible squigs.
• Juicy Squig - A rare type of Eatin' Squig.
• Growler Squig - A variety used to shepherd Gretchin. (Also known as a Squighound.)
• Oily Squig - A variety bred by Meks to use as fuel for the Ork's ramshackle vehicles.
• Attack Squig - Voracious beasts used to attack enemies.
• Face-eater Squig - "Gnashers". Toothed variety used both as a weapon and in face-eating contests. (The Ork and the Squig both open their mouths and bite, in a parody of a kiss. If the Ork eats the Squig, he wins. If he keels over backwards, he loses.)
• Squiggoth - Gargantuan creature ranging in size from an elephant to a 60-plus foot animal capable of destroying buildings by crushing them. Often used as pack animals and carriers or mobile fortresses.
• Orkeosaurus - A larger version of the Squiggoth but only seen in Epic 40,000.

Sources

1. Codex: Orks (4th Edition)
2. (September 1987) White Dwarf (145)
3. Evolution of Tyranids - Australian GW website (Accessed 2008.11.12)
4. Waaargh: Orks