So how do those little brown crickets that you find all over, hopping around in your yard in mid-summer. How do they get there? Where do they come from? And how do they get in your house?
They thrive on your yard's seed pods, from your plants decaying organic matter and they survive with the water drippers that are on the base of every plant they burrow down underneath the roots of the plant and eat the roots and so forth and really thrive in this environment. Now when it gets hotter or the drip system isn't working quite right or their population is too large, they eventually make it to the foundation of your homes.
If you can see this little dirt looking material here it's actually fecal matter left by crickets who have colonized the wall through that gap. Gaps like these are common all the way around the foundation of your home and are often left by the builder to allow moisture to escape from the air from the walls; however, that moist air is an attractant for the crickets. As you can see there's quite a bit of fecal matter.