I don't understand the cucumber beetle lifecycle. Last year I had them. I like to grow squash and cucumbers among other vegetables and for some reason, have never had a problem in over 20 years of growing these plants. Last year I started seeing all kinds of damage and the local extension agent told me what they were. I treated them with some soap and that was that. The other day I started to clean up my garden getting ready to plant and I saw some under some old leaves. How can they be back already? It's early spring and there is no way they have been able to reproduce yet.
Cucumber beetles overwinter. In other words, they hibernate and don't die at the end of summer. What you didn't kill last year will hide themselves for the winter and then emerge at the first signs of spring. I'm sure that's what's happening now.
To stop this from happening, you should clear away all the old plants at the end of your gardening season as explained in our CUCUMBER BEETLE CONTROL article. These plants will surely attract local cucumber beetles and by letting them stay on your property over winter, they'll cause damage to any thing growing in your yard the following spring.
Since you've seen some activity now, either treat again with the INSECTICIDAL SOAP or some VEGETABLES PLUS to knock them out before you start growing your new spring garden. The cucumber beetles you just saw represent just a few of the ones that are probably present and if you allow them to live, they'll mate and start laying eggs in no time. In other words, if you don't treat now, you're bound to have a much worse problem later this year.