RR sends this in, saying they are genuinely stumped.
The problem with an explanation that they are afraid of spiders is that spiders would naturally be all over ships of this era, along with various other vermin. So is there another joke we’re missing here?
Comics I Don't Understand 
The title of this strip in Perry Bible Fellowship’s website is “Invasion”. Maybe the joke is that while the Vikings are invading a foreign land, the spider is invading their ship?
We’re supposed to think they’re running toward a village to pillage it. But they’re running away from the spider. That’s it.
I’m with sheep and Powers. You’re meant to think they’re invading the village, but they’re fleeing a spider that invaded their ship.
As to spiders being common, that’s overthinking the joke. It is an exceptionally large spider though.
Is that a grimacing face in the center of the web? Or have I just read Charlotte’s Web one too many times?
“EDDERKOP!”
Perry Bible Fellowship is often dark humor. Sometimes just dark. I assumed the Viking invasion failed completely and the spider and web are a sign of the time that has passed between panel two and three.
The title of the comic is invasion. The Vikings have invaded the village and now live there. In turn the insects and spiders have invaded their ship and now live there
Powers has it.
I don’t see a face, larK.
I see a smiley face, just a circle, two dots for eyes, and a ) for a mouth. I’m sure it’s just pareidoilia, though.
My initial thought was that the ferocious group of warriors attacked the village and never came back. Perhaps the village more dangerous than appears. However, the “afraid of spiders” is probably correct. But I _like_ mine better, so I will believe it instead.