From the photo of the leaf underside it looks like thrips - there is an adult clearly visible and you can also see the white casts - that is the skins that the insects cast as they molt. Unlike insects such as butterflies which pupate from a caterpillar that looks nothing like the winged adult, thrips go through two nymphal stages and an inactive stage where they develop into adults. Insects possess a rigid exoskeleton which serves much the same purpose as our own skeletons (i.e. muscle attachment) just that it is on the outside. The nymphs must shed this exoskeleton periodically to allow more room for growth. This is what you can see in your picture - I've highlighted it in the attached image.

As far as the species, I'm not entirely sure but the clear dark stripes on its back resemble that of onion thrips. I've attached an image to see if it aids in identification.

In terms of control, you can prune out really heavy infestations or try to spray them off with a jet of water. Make sure you provide the plants with adequate water to avoid further stress and do not overdo any nitrogen fertilizers as this will promote the insect population on the plants.