The unknown brown bugs are no longer unknown. They are "squash bugs," or Anasa tristis. No wonder they are found only on my pumpkins! It sounds hard to get rid of them. How do they find their squash in the first place? There was no garden here before this year. On online hint says to make a circle with regular flour around the plant stems. Apparently squash bugs do not like to walk in powder, or alternatively, they eat it and it gums up their mouths. Neither sounds very logical, especially the walking bit, as they have wings! Why walk on the ground when you can fly onto it from above? Oh, well... the solution is still to hand pick them off and put them in soapy water.
My son and I checked the underside of EVERY pumpkin leaf, finding lots of eggs have already been laid! Most were on the leaves, some were on stems. I poked them off with a pencil and finger, into the soapy water cup. We found only 4 bugs this morning, but 2 of those were in the process of mating! "Two for one," as the Master Gardeners told me!
I have grown pumpkins many times before and never had squash bugs. The adults winter over and come out to fly around looking for squash plants. Maybe no one grew them near me before. That is likely, there are many more backyard gardens and farms in my neighborhood now.