In crustaceans and insects, all of these functions are served by specialized anterior mouthparts on the head of the animal for processing food before ingestion.However, in trilobites, most of the processing occurred in the longitudinal medial groove between the limbs, with their repeated pairs of gnathobases, meaning that the "mouthparts" of a trilobite occupied the length of its underbody, rather than being primarily anterior.Modern crustaceans in those situations (as at mid oceanic ridges and thermal vents) often live in a symbiotic relationship with sulphur-eating bacteria that are housed in the gill structures.
Once subdued, the gnathobases will tear the worm apart and feed chunks into the mouth.
Although it is argued that trilobites with conterminant hypostomes were probably primarily predatory, a large proportion of trilobites (such as Modocia at right) have natant hypostomes, which Fortey and Owens suggest indicate a shift away from predation and into particle feeding, which includes scavenging for bits of benthic detritus (as the group of olenids below might be doing), or perhaps grazing on beds of algae.
Ned Sherrin selected it for inclusion in the Oxford Dictionary of Humorous Quotations, being introduced in the third edition in 2005. 'He was kind of famous; he was big and black; most important, he was an American, one of us, not some cheese-eating, surrender specialist Froggie.' In the anime/manga webseries Hetalia: Axis Powers, in an episode, England angrily referred to France as " You Cheese-Eating Surrender Monkey!
Trilobites occupied a huge set of habitats and paleolatitudes, from tropical shallows and reefs, to polar depths, and wide-ranging pelagic habitats in between.
Fossilized trilobite trails sometimes stop when they intersect worm burrows (suggesting that the trilobite was hunting for worms, and stopped to eat when it found one in its burrow).
Presumably the worm was extracted, subdued and crushed or torn apart with the leg spines and strong gnathobases, then passed forward between the legs to the anterior mouth, where last processing was done against the hypostome platform before ingestion.
Finally, since there are few depictions of trilobites eating anything, here is my reconstruction of a large Olenoides serratus, subduing a small Ottoia (a priapulid worm) that it has just pulled from its shallow burrow.
Its spiny limbs pin the hapless worm to its ventral midline, where its large gnathobases stab and tear at the worm's tough outer epidermis.
Another piece of inference on the predatory nature of early trilobites can be gained from looking at the relatives of trilobites.
The sister-taxa of trilobites, such a Naraoids, also included predators (see the fang-bearing gnathobase of Naraoia compacta above, for example).
Predatory trilobites, argued Fortey and Owens, would need to have conterminant hypostomes (firmly attached to the frontal doublure), essentially stabilizing the hypostome against the cephalic exoskeleton for aid in processing prey.