A bunch of these guys that ride around on giant arachnids to try and stop that bad guys! The badguys are really evil, and ride scorpions, and the spiders talk!

Underneath the surface of the Earth lies the Inner World, a realm where a war rages on between intelligent spiders and the invading humanoid insects known as Insectors. However, the spiders are not alone, as "Spider Riders"-humans from the Outer World, known as Earthens in the Inner World, that are chosen by the Oracle-fight alongside them. Filled with wondrous tales of a mysterious pyramid and entrusted with his grandfather's journal, a young boy called Hunter Steele sets out on an exploration. There, his destined meeting with the Oracle occurs, and he is transported into the Inner World as a Spider Rider. Finding himself lost and confused in the middle of a forest, Hunter crosses paths with a giant spider named Shadow. Although reluctant, Shadow agrees to fight by his side. He then meets Corona-a skilled Spider Hunter and kind girl with a penchant for normal life. She shows him the ropes of being a Spider Rider, and educates him about the fate of the Inner World if the Insectors continue their tyrannical reign. Thus begins the story of Hunter Steele, a heedless young boy on a quest to save the Inner World. But his task of retrieving the four Oracle Keys holding the Oracle's true power will lead him to an ultimate clash against Mantid, leader of the Insectors.—MAL Rewrite

Fourteen-year-old Hunter Steele searches for the legendary Inner World by following the instructions in his grandfather's journal. He enters a cave where he finds a mysterious manacle that attaches itself to him. A spider startles Hunter, who falls into a hole to the center of the Earth and into the subterranean world of Arachna. There, he discovers a small group of elite warriors struggling to survive and to save Arachna from the attack of humanoid-insects called Invectids. The warriors are children, each fighting with the help of their own 10 ft. (3.0 m) battle spiders. They call themselves "Spider Riders". In the English TV series, the ages of the characters were reduced. There is a prophecy that says a surface-dweller or Earthen, like Hunter, will bring disaster to the Inner World. Sparkle mentions it in the beginning of the series. When she learns of Hunter's appearance in the Inner World she wonders, "I wonder if he will bring doom to us...or to them."—Spider Rider Center

Spider Riders (Spider Riders: Oracle no Yuusha-tachi, Spider Riders ~the Heroes of Oracle~) is a series of science fiction novels first published in December 2004, published by Newmarket Press written by Tedd Anasti, Patsy Cameron-Anasti and Stephen D. Sullivan (books 2-3). The stories became the basis of the animated television series produced by Cookie Jar Entertainment of Canada and Bee Train of Japan. The three novels are titled Spider Riders: The Shards of the Oracle, Spider Riders: Reign of the Soul Eater, and Spider Riders: Quest of the Earthen. Spider Riders broadcasts on Teletoon, This TV, and Kids' WB!. Koichi Mashimo co-directed the staff at Bee Train with Takaaki Ishiyama. Writer Yosuke Kuroda adapted the novels. Robert Pincombe and Shelly Hoffman wrote the English version.—Spider Rider Center

Within the Earth exists the Inner World, created and blessed by a being known as the Spirit Oracle. There, a war has been waging between the humans and Insectors/Invectids. Following the journal of his late grandfather, 13-year-old Hunter Steele finds himself drawn into the Inner World. He soon encounters the independent spider Shadow, who eventually becomes his partner, as well as the mysterious girl Corona, one of the elite warriors known as Spider Riders, who welcomes Hunter into their team. Along with Corona, Igneous, Prince Lumen, Princess Sparkle, and the former wanderer Magma, Hunter fights against Mantid and his Insector army, trying to prevent them from collecting the four Oracle Keys. Though the English dub's initial run in the US was cut short note , it did receive a full broadcast in Canada courtesy of Teletoon. There is also a novel series, online game, and canceled manga as part of the franchise.—TVTropes