- "This guy was tiny, no more than two inches from the end of one outstretched leg to the end of the farthest back leg. A toddler could easily crush him underfoot. But I guess it isn't size alone that makes a predator, because as soon as I felt the edge of that spider brain I knew this boy was trouble. The wolf spider was a killer."
- "I reached out a finger to touch the spider. It was shaking. My finger, not the spider. I touched the spider's back. It tried to get away but Cassie closed her hand around the spider and the tip of my finger. The spider became very still as I acquired it. Thanks to the Andalite technology that had transformed me, the spider DNA entered my system."
Discovering the Chee
- "This is a wolf spider. It has pretty good eyesight. In fact, it has eight eyes." [...]
"We need good vision, but not standard mammal-type eyes. And we can't all go in the same way. I want two people to hang back as a rescue squad in case we get into a mess. Ax has to go because we need him to see if he can figure out what Erek is. Ax is going in as a spider, and we need someone to go with him."
- ―Cassie and Jake
After Marco and Tobias discover that Marco's old classmate Erek King is not really human and that he might be using a hologram to mask his appearance, Ax suggests using a morph with eyesight not similar to humans, since the hologram would be attuned to human sight. Cassie finds a wolf spider and decides that its sight would be able to penetrate the hologram, and tests its vision out. Since Ax is the only one out of them most likely to identify what Erek might be, Ax acquires and morphs the spider as well, with Marco reluctantly chosen to accompany Ax.
While crashing a mountain lake party hosted by The Sharing, Ax and Marco are able to see through Erek's hologram using the wolf spider's eyes. Marco is then snagged by a crow, who attempts to eat Marco; Marco begins to demorphs and bursts through the crow's throat, landing on the ground below and finishing his demorphing, only to realize Erek has witnessed the event.
During the Animorphs' attempt to infiltrate the Matcom Corporation building to retrieve the Pemalite crystal, Marco and Ax use their wolf spider morphs to spin silk and descend through the vent, with Jake, Rachel and Cassie, in cockroach morph, using the silk to descend as well.
Retrieving the Escafil Device
In order to retrieve the Escafil Device from a boy named David, Jake has Marco and Ax break into David's house and prevent an e-mail with David's location from sending out to Visser Three, who wishes to acquire the morphing cube. After David's father abruptly returns home, Ax hides in the closet and uses his wolf spider morph to prevent David's father from seeing him as an Andalite, although he is forced to demorph in front of David's father after Marco, in king cobra morph, accidentally ingests him and injects him with cobra venom.
Yeerk Compound Infiltration
- "In the end, after some debate, four Hork-Bajir headed stealthily down toward the secret Yeerk facility. On board them was a collection of insects. A flea, a mosquito, two cockroaches, one housefly, and a wolf spider. Marco was the spider. [...] Unfortunately, I couldn't see anything from my vantage point at the base of Jara Hamee's front horn. I mean nothing. But I could listen to a running, thought-speak description courtesy of Marco. He, after all, had eight eyes."
Marco elects to use his wolf spider morph, as opposed to a flea, mosquito, housefly or cockroach morph, when the Animorphs infiltrate a Yeerk facility located out of town. Due to the fact that he possesses superior vision compared to the other Animorphs, aided by his eight eyes, Marco uses the morph to notify the others of their surroundings.
- "With eight legs, each the size of the Saint Louis arch. Gnashing, wickedly sharp mouthparts that looked like the gates of hell. A swollen, stinking, bloated, hairy body. But none of that was what made Marco and Tobias and me shake with uncontrollable fear. It was the eyes. Eight of them. Some were glittering, multifaceted compound eyes. Others were blank, dead, black simple eyes."
After Cassie, Tobias and Marco are shrunk down to one-sixteenth of their size by the Helmacrons, Ax uses his wolf spider morph in order to locate them, as he was the only one who was not shrunk who possessed a morph capable of spotting them.
- "I was not the ideal choice for the task, what with my recent morphing problem. But only Cassie, Ax, and I had the morph needed, and Ax couldn't be trusted in a kitchen in human morph. Far too much tempting salt and grease. And we needed Cassie with Jake and Rachel. So I got the job. [...] Morph to wolf spider, run out to a spot directly above the salad, drop into said salad, bide my time and scare the pee out of Tennant. Roaches and a spider? No one can see all that in his salad and not become slightly disturbed."
Marco attempted to use the wolf spider morph to contaminate talk show host William Roger Tennant's salad, in order to take advantage of Tennant's rage issues and cause a public tantrum, which would ruin Tennant's image and render him ineffective as a recruiter for The Sharing. However, due to Marco's inability to control his morphing at the time, Marco inadvertently fused his wolf spider morph with his skunk morph.