What are these?

I started noticing a couple of days ago that my young spinach plants have clumps of translucent and VERY tiny (immeasurable with any ruler I have) structures. I know spider mites are supposed to be very small, but I haven't seen any of these move. I am wondering if these are eggs of some sort. They are mostly at the center of the plants, where the leaves all connect and where new growth comes from, as well as being on the backs of the newer leaves- not so many on the larger ones. When clustered together, they have a whitish appearance, but they are more translucent individually. I tried taking them off by hand (not individually, obviously). They seem to have a firm texture and a round shape when I rolled them around between my fingers- they didn't break under some pressure from my fingers (I really wasn't attempting it too much, didn't want the mess on my hands from whatever they are!).

The first picture is a reference- I am holding a small spinach leaf with the "objects" on it- this is to get an estimate of how small they are. The second is a closer shot, as best as I could enlarge and still be clear. You can click on the pictures to enlarge them, of course, and will probably need to to even see what I am talking about.



I got some organic fungicide/pesticide that supposedly helps control spider mites as well as leafminers (have some of those on my spinach as well, but hardly any- I picked off the leaves that I saw with the damage and egg cases, haven't seen any since) and will control other insects in adult, egg, and adolescent stages. I have only tested it on one plant this morning to see how it handles it, but of course, it is too early to tell.