"I agree - " Liam starts to say, then stops and frowns. 

He hesitates, clearly wrestling with whether to actually say what's on his mind.

"...how sure are we that no-one at this table is compromised?" 

"Lydia and I are sure we're both safe, but that's not evidence. Want to convince all our parents to let us go on a weekend camping trip?"

"Are there any animals with x-ray vision? That would let us see them."

"Most animals can see x-rays, but that's not anything like the superpower."

"I guess even if you have x-ray machines at the vet clinic, they won't be set up for humans," Rowan muses. She's mostly thinking out loud at this point, rather than proposing actual solutions.

"And you'd have to explain why you wanted to use it, I suppose." 

"We don't actually have them, anyway. It's a small office, we're not really set up for that. My mom is a nurse at the hospital, which does have them, but..."

"But that still has the problem that we have no legitimate reason to access them," Liam agrees.

"It doesn't sound like x-raying people is the solution, unless there's a type of alien with x-ray vision we can borrow." 

"Not any I know about."

"What do you know about them? How many kinds are there? Smart ones, not animals. How many like us?"

"He might not have known about all of them, and he didn't send me everything he knows. I know about seven, but I don't know a lot about them."

"That's still more than the rest of us know," Rowan points out. 

She's already reaching for a notebook and pen. 

So she tells them.

There are Andalites, who they've seen. Female Andalites are purple, not blue, and usually smaller. They graze using their hooves to absorb nutrients, and they hate enclosed spaces.

There are Garatrons, similar to Andalites but without the stalk eyes or the tail blade, known for their speed (it's more like a superpower than anything Allison can think of on Earth).

There are Gedds, primates with webbed toes, who are slow, weak, and nearly blind. They're native to the same planet as the Yeerks.

There are Hork-Bajir, tall dinosaurs with sharp blades at various joints on the body, which are herbivorous but nearly all infested.

There are Leerans, psychic aquatic frogs who see any invasion attempts coming.

There are Taxxons, giant centipede-like people who accepted voluntary Yeerk infestation to help sate their insatiable hunger. They're cannibalistic when not supplied with enough meat.

There are Skirt Na, who look like giant bugs, until they metamorphose into greys. They're known for abducting and experimenting on non-spacefaring species.

"Are the actual literal greys who abduct people using flying saucers?"

"Yup."

"We've seen Taxxons and Hork-Bajir, right?" Liam thinks back to the aliens they saw the previous day.

"Let's worry about those first since we know they're on Earth with the Yeerks. Do you know anything that might help us deal with them?" 

"Taxxons are really hungry. If one of them is hurt, they start eating each other. The Yeerks try to avoid using Taxxon-Controllers on Earth, but any room with one in it is a valuable target."

"Ew," is Rowan's response to the cannibalism, but she writes it down anyway.

"So we could take out a whole group just by injuring one?" 

"Only if they don't have Yeerks in them at the time. Right?" 

"Yeerks can only do so much to prevent it. That's why they're don't like using Taxxon Controllers."

"So it'll be an effective strategy, exactly once."