Q:I just found these on one leaf of my highbush blueberry bush. Are they the start if those horrible yellow neck caterpillars?
A:Your suspicions are correct – they are immature yellow necked caterpillars, probably Dantana ministra.
If you allow them to develop into adults they will consume many leaves.
Fortunately, a quick spray with a product that contains Bacillus thuriengensis. will easily control them.