Mecannibals are mechanical lifeforms that "eat" other mechanical lifeforms. They are faintly reminiscent of spiders, except with only four spindly little legs attached directly to a rotund red body, which appears to be mostly toothy mouth, below a pair of malevolent yellow optics.
Mecannibals reconstitute their prey back into their component parts (or at least, PARTS of their prey), which they have been known to sell on the black market to unwary or unscrupulous buyers.
Their leader is Master Mouth.
Marvel Comics continuity
While at the Grand Central Space Station, Cloudburst and Landmine were on assignment from Optimus Prime to find special microchips to repair casualties of the Underbase fiasco. The pair made a deal with Hi-Test and Throttle, the Nebulan Powermaster partners of Dreadwind and Darkwing.
They led the two Autobots to the Meccannibal's ship, located not far from the Space station. The Nebulans introduced them to their employers, the Mecannibals, led by Master Mouth. The Mecannibals were not aware that the two Autobots were robots, thanks to their Pretender shells. The business deal was interrupted when the Mecannibals rolled out Sky Lynx, whom they intended to have for supper. Landmine and Cloudburst managed to set their comrade free, but in the chaos, accidentally revealed their robot identities to the Mecannibals and wound up on the menu.
About to be devoured, Cloudburst and Landmine managed to talk their way out of being eaten by promising to go to the planet Femax, obtain a rare spice of lead sulfide crystals and return with the garnishing; receiving the microchips they need in return. As collateral, the Mecannibals held onto Sky Lynx's human buddy, Berko. After a series of rascally and erotic hijinks on Femax, the pair returned with the crystals and freed Berko. However, before leaving, they revealed to the hungry Mecannibals that the Decepticons under their employ were, in fact, robots. The Mecannibals, outraged over being tricked, chased the pair of frightened Decepticons out into deep space, determined to eat them.
The pair eventually lost the Mecannibals, or so they thought. In reality, the Mecannibals followed them back to Cybertron.
Feeling like losers, Dreadwind and Darkwing chose to drink away their sorrows at Maccadam's Old Oil House. The Mecannibals followed them to the pub, eating their way past Rocky, the bouncer. The Mecannibals immediately began tearing up the joint, with the pair of inebriated Decepticons blissfully unaware of the chaos around them. Luckily, Quickswitch was present and leapt into action. After a brief skirmish, Quickswitch used his tunneling mode to bury the Mecannibals alive deep underground. The Mecannibals were last seen trying to eat their way out of the pit they were trapped in.