I also have this problem. It is squash bug eggs. They are on the underside of leaves wich have high water content. They are similar to leaf footed bug and the cotton strainer.Cut off the leafs with these eggs on them and throw them in the garbage or fire (away from the garden) They are bad bugs. They suck the juice out of the tomates and leave them bitter. I have tried soap and oil sprays and found them to be non effective. I have been using sevin dust and reappying after it rains. You have to really cover the plants with it though.