How are we supposed to tell when to heal our spiders with the healing glop?

[Alienm]

Since spiders don't regenerate health by themselves and we got an item to heal spiders in an area of effect, how are we supposed to know when to heal them?

This has become kind of important information now, especially since the  switcherdoodles cost a lot of resources, so if our upgraded spiders die because we didn't know how much health they had, it seems kind of unfair.

Please don't tell me I have to download a mod.

[BezKa]

You don't have a way to know mobs' health. The only ones that show it somehow are bunnymen, and with all other followers you have the same problem. 

I doubt anything will be added to compensate. You're much better off just having a nurse spider around that will heal your spiders periodically for free.