We lived in southern Arizona for 6 years. Insect pests troubled my garden and I know that spiders eat insects, so it seemed reasonable to introduce spiders into my garden. Not just any old spiders, what I had in mind were giant spiders, tarantulas, in fact. I figured big spiders would have big appetites and eat a lot of big insects.
In southern Arizona when the monsoon season starts in the summertime, tarantulas go on walk-about; literally thousands blacken the rural roads. I took a five gallon bucket and scooped up a bunch of the rascals, put a lid on the bucket, and when I got home, I dumped them in the garden to feast on insects.
Next morning I inspected the results, not a spider in sight! Apparently, they walked off in the night. I found one smashed in the street, but that was it.
Later, I learned why; it has to do with sex, procreation and all that stuff. It seems the females seldom venture more than a few feet from their underground burrow, but in mating season, they emit powerful pheromones. The males then go on walk-about in search of females. The guys I captured were all males looking for love, and my garden was the wrong place!
I've heard this a lot through the years. I saw the most beautiful one down near Concord CA, out in the country. It was a brown I think but looked a bit red, pretty. I stood back, but my little dog, on a leash, saw it before I did and she went right up sniffing it. Scared the beegeebies out of me and yanked her away but I notice it just kept a walking, like it knew she wasn't a threat or something. That's when I got to understanding them a bit better. It really is about education isn't it.I have had Tarantulas for pets a couple of times. They are gentle and interesting spiders. They love to eat crickets. It is amazing when they crawl out of their old skins as they grow.