Are they pests? If you have not identified them then you cannot call them pests. Spraying broad spectrum poisons around, that will also kill off the beneficials that might be wanting to eat these, is never a good idea.
Aside from a large number what damage is being done?
What species have you eliminated from consideration?

I think they are baby spiders, too big to be spider mites, unless your flower is smaller than it seems in the pic. If so, they are probably off to find other bugs to eat, good guys in the garden.

are spiders insects??

if not.. that would answer why an insecticide didnt work .. see link

put down the chemicals.. and step away ...

we NEVER apply anything .... until we ID it ... thank God you found us.. lol ... [lets keep our fingers crossed.. that they are spiders, or it blows my whole thanking part.. lol]

and though you may not like spiders.. in the house.. you should never bother them out in mother nature.. they really are beneficial ...

ken

Here is a link that might be useful: go figure

Though spiders are not insects, they can still be killed outright by a number of common insecticides...Sevin amongst them. Sevin is highly toxic to lots of things; it's deadly to earthworms, for example.

I think that these are spiderlings, too. And as Ken says, it is
something of a cardinal rule that identification comes first THEN control. Hopefully, a hoard of the little ones will survive to protect your garden. Look for the adults later on and don 't be 'skeered'.

I'm going with spiders as well. Almost looks like an adult red ant mimic spider up at 2 o'clock on the pic.

tj

They look like chiggers. I get them every year. They cover my plants for a few weeks - persistent little boogers - but they never really do any harm. You can take the water hose to them if you need to put your hands in those areas. I don't know if it's the weather or something that eats them, but they always go away and never really do any damage. I can't tell from the picture, but are they webbing at all? If so then definitely not chiggers and I'd go with the baby spider idea. And Ken, I'm with you on leaving them alone in the garden. I HATE spiders. Lol So in the house, it's fair game. But in the garden, I hate damaging insects more so spiders become the good guys. They can hang around and eat all the aphids and mites to their little hearts content. I still don't have to like them, I just have to leave them alone. Haha. Nature has a way of balancing itself without our help. I've learned the hard way to leave well enough alone!

Not chiggers, which are extremely small and not typically found crawling all over plants. They do not make webs. They are a parasite of humans (and other animals), causing an intense itching at the site of their little bites.

What jentiffany may be seeing is an outbreak of clover mites or similar. These might even be what our original poster has observed. They tend to swarm an area for a short period of time then disappear as quickly as they arrived.