If you build it (or plant it) they will come... I think it happened when Eve ate the Apple??

I can remember the first time I planted potatoes, and we live far from anyone else. The potato beetles showed up immediately, and we'd never seen them around here before....ever. Its just amazing. Its like they must live dormant in the earth for centuries, and as soon as they smell the plant they like to eat, they rise up. hahaha
Its one of those mysteries of the universe, I guess!

And to answer your question, YES, unfortunately you will see bugs in your raised beds. I have RB that last year had okra, turnip, chard, basil, cucumber, watermelon and squash(which I planted late in an attempt to miss the SVB, they still got wiped out by the SVB, my okra, watermelon, chard, turnip almost always had stink/squash bugs on them and then one other type of bug some kind of small beetle? I routinely hand picked them off, searched daily for eggs and nymphs, I was diligent at picking them off. I learned to anticipate them jumping off the plant as I approached, but I was ready with my cup of soapy water just below, I made them a suicide diving pool..that part at least was fun.

My tomatoes last year were nearly infested with the leaf footed bug, and that is a horrible bug, they literally will fly at you and attack, and they are nasty looking too. I would sneak up on them with a spray bottle of something to knock them down, or immobilize them and then I hacked them in two with scissors. It was that or hit and miss with the scissor approach first.. I was not about to hand pick them!!!

I wish I knew what actually happens in the universe to deliver them to the plants that they intend to destroy. Why cant them feed on other plants and NOT the plants we want to grow for food??? It's really amazing how that works. (to our dismay)

Well, just to pick a random pest you mentioned:

http://www.ipmcenters.org/cropprofiles/docs/TNsquash.pdf

The spotted cucumber beetle is about 1/4 inch long, yellow to greenish-yellow with 12 black spots on its
back and a black head. They overwinter in the adult stage near plants and in debris. Some migrate south
and have been known to travel 500 miles in 3-4 days.

Bugs are born to their parents. (grin!)
They are out there. We don't see them untill they eat our plants.
Also, most of them are pretty mobile, have wings, can fly.
The best way is to prevent/repel them.Last resort kill them.
Preventive medicine and preventive insect damage is the wave of future, shaping up now. But big chemical companies want to sell their products.

Thank Internet! The knowledge and informations is spreading at the speed of light. The world libraries and more are on your desk top if you can use it.

No more secrets about "How They Do It", "How to Make It",
"How It Works". Google/Yahoo are intrusive but they can give you a lot of informations.

Just search : "Where do the bugs come from?"

Tomorrow, somebody might just read this post, when he searches "Where do the bugs come from?" (haha)

He might not be able to find the "final answer" but he can get a philosophical perspective.

Isn't Gardening Fun?!

Most garden insects have a flying stage, and they'll migrate huge distances looking for hosts. They are apparently attracted by either the chemical "smell" of plants they like, or in the case of the good-guy pollinators, sometimes by the UV color emitted by blossoms.

All you can do is anticipate that you'll get some of the pests as well as some of the good guys and be prepared.

I often wonder too, but if you grow they will come.. haha
If you take a look in your soil you'll find all kinds of insects. Soil outside is anything but sterile.
Some things I found in my in and around my soil, grubs, beetles, worms, white flys, spiders, red mites, lady bugs and ants. I've learned not to be so grossed out by it. The insects are probably more afraid of you, then you them.

Try not to get paranoid. The sole purpose of everything on this earth is to reproduce. The plants that each bug eats are what helps them survive to do that. Yes, I'd prefer it if the tomato hornworms, the bean beetles, the cucumber beetle, the squash bugs, etc., preferred to eat all the invasive japanese honeysuckle that is all over my property.......but that's not how it works, unfortunately.
You just have to try your best to protect your various plants from the guys who need them for survival as best you can. We're interfering with their plans too! :)