Spydorz
A Spydor is a pest that will teleport into a person's house at random and attack their Chibi-Robo, often in packs of three to five, with only a few drops of oil to warn of their presence in an area. When first encountered in Chibi-Robo!, however, there were eight Spydorz in the group, which surrounded Chibi-Robo in an attack called the Spydor Roulette. While Spydorz are a menace, they are easily taken out by a shot from a Chibi-Blaster; these shots will conveniently home in on the nearest Spydor. Destroying a Spydor will leave behind a bit of Scrap, which can then be recycled in order to create Utilibots. Even with their queen destroyed, the Spydorz continue to appear in the Sanderson household.
Creation
The Spydorz were in fact created by Mr. Sanderson, while he was an employee of Macroware Robotics, Inc. Though he had designed them to be friends with Chibi-Robos, the company reprogrammed them to attack. Mr. Sanderson quit as a result, taking the more dangerous Spydorz with him. When Mr. Sanderson heard from the news that Spydorz were attacking Chibi-Robos around the world, he became quite upset.
Construction
Since the Recyclotron in the Chibi-House can use Spydorz components to make Utilibots, it is quite possible that the Spydorz themselves are made from scrap too. Since the Spydorz Queen uses smaller Spydorz for ammo, it's possible that she has a built-in Recyclotron. It is also likely that normal Spydorz can upgrade each other, as evidenced by the fact that, when the suitcase containing the upgraded Spydorz is opened, only four come out-without a Queen. In fact, it is also probable that these bigger Spydorz took apart the lesser versions to help construct their Queen, the Queen chose to cannibalize the smaller Spydorz that could teleport into the Sanderson household freely as parts for her improved, four-legged versions. It is also highly likely that Macroware Robotics has dozens of Queens at their factories, making even more Spydorz, or that there are simply Queens other places that are churning out normal Spydorz. The only reason the upgraded four-legs are absent among the race of the simpler two-legs is that the other Queens simply don't have the designs for them.
Purpose
It is unknown why Macroware Robotics, Inc. decided to reprogram the Spydorz, originally intended to be friends and possibly helpers to the Chibi-Robos constructed by Cytrussoft, to attack the little robots. It is possible that they were trying to eliminate the competition, though; on top of dwindling numbers, it would be much more expensive for other people if the Chibi-Robos were having to use energy to avoid (or blast) the Spydorz on top of all the cleaning.