There are a variety of insects on the bottom of this kale leaf in the attached photo. I would appreciate it if you could identify them. I am particularly interested in the red larval-looking insects because there are many more of them and they are focusing on my mustard greens (the kale has been relatively unscathed). I think they are aphids. The plants are growing under a thin row cover (I keep it on to deter cabbage butterflies and harlequin bugs). Thanks for your help.
The red insects look like aphids. We also see that there are a lot of parasitized aphids (called "mummies") which is an indication that you have good beneficial insects (natural enemies) at work on the pests. A good sign! https://extension.umd.edu/hgic/aphid-parasitoids The black insects might be secondary, coming in to feed on honeydew produced by the aphid feeding. https://extension.umd.edu/hgic/aphids-vegetables