Based purely on my experience, Starlings have the ability to sniff these out from quite a distance and descend in hoards onto any feeder in which these dried mealworms are placed, staying until they have eaten the lot, which is not very long. They clearly love them, as do any other birds that manage to get a look in.
I tend to place the dried worms on a ground feeder so that all bird types have the opportunity to feed. I have tried one of the special covered mealworm holders that had a mesh surround meant to prevent Starlings feeding, but the Starlings around here were clever enough to work out that if they all landed on one side, the feeder tilted and they were then able to reach the worms, albeit feeding at a slightly slower rate.
It is possible to buy live mealworms but having tried that once, I decided I am not keen on having to look after death-row inmates and I now only buy them dried. The birds seem to like them dried just as much as those that are fresh, so have not petitioned for a change back again.