I had seen clusters of these insect eggs on kale and other plants in my garden a number of times this spring. The first time I pinched them reflexively, then tried to determine what they were without success , the second time I left them alone, thinking they might be something helpful. The third time, there was a huge cluster of them, and I took them to the Leon County UF/IFAS Extension office where Horticultural agent Mark Tancig and his assistant Kelly Thomas solved the mystery.
They are indeed good bugs, and they are not eggs at all. If you look close, you can see they are a little fuzzy. They are the cocoons of a parasitoid braconid wasp which preys on the cabbage butterfly. The cabbage butterfly larvae feed on the cabbage, and the wasps, which can be as small as 1/8" lay their eggs on or in the butterfly larvae. The eggs hatch and eat the cabbage worm from the inside, emerging after killing the host caterpillar and then spin this cocoon, eventually emerging from the cocoon as a new wasp to repeat the cycle. You will see a little black spot or hole in the end of the cocoon when the wasp has emerged.
There are over 15,000 species of braconid wasps identified worldwide with over 2000 in the US, and many more which are unidentified, maybe as many as 50,000 species. It's mind boggling. Braconid wasps also prey on other insects, including aphids and some beetles. As adults they are pollinators, feeding on nectar and pollen.
For more information about these non-stinging little helpers and how to attract them, refer to an article in Mother Earth News along with some university links furnished there.
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