More insects in stream bottoms. Actually, the riparian spiders have webs that are too large for their needs. This seems to be due to influx of spiders from desert. Resource defense polygyny. Dear Enemy Hypothesis.
Territorial animals learn their neighbors and the borders of the territory.
Neogonodactylus bredini molting and increased aggression just prior to molt. Learning the attributes of a territory make it more valuable. Hazlett.s study on crabs, fish and rodents. Used identical design. One species territorial, the other not.