It's hard to tell from the photo, but maybe some kind of Sawfly larvae? Can you describe it for us? Length, legs, head, tail?

If they're Sawfly larvae, try insecticidal soap spray.

Perhaps the larvae of a leaf-eating beetle?

How many and on how large a shrub? I ask because it could be possible to flick them into soapy water. However, if you have lots, the direct hits of insecticidal soap may work just as well.

....the little black "dots" you see are their fecal matter. Whenever you DONT see cats this is a good indicator.
Sorry don't know your specific creature, but as Jean suggested and if it were me, I would be out there with a soapy bucket of water and dropping every one I could find. But before you kill them all, I would take one to the local county extension office and see about a positive ID.

Vera

I wish I could recognise the shrub, as sawflies are VERY species specific. Knowing what kind of plant it is would be most helpful. At this point, it could be sawfly, beetle larvae, and even caterpillar.

I would absolutely follow Jean's and Vera' and Donn's recommendations for physical removal. We could ID it, I am sure, if we knew the plant.

The plant is an Arrowwood. The little caterpillar like bug is about 1 cm in length.

Thanks so much for your suggestions. I'm going to get out there tonight and get rid of them with a soapy bucket of water.

Aha! Viburnum Leaf Beetle (Pyrrhalta viburni) larvae.

Here's a pic showing two of the three different larval stages:

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Get them before they mature to adults.

Thanks Donn! I appreciate having a name for this critter.

Now that we know your plant is a viburnum, your earlier images ALL OF A SUDDEN seem perfectly clear, lol!

These insects have a great many predators, so I would use the least toxic product possible to get rid of this infestation. Hand picking would be best, strong sprays of water, or insecticidal soap applications.

Attached is an image of the adult, by the way.

Here is a link that might be useful:

Does anyone know if BT would work on the larval stage of this bug? It sure looks like a caterpillar.

Matt

Nope. Not a caterpillar at all, but (as Jean said) the larval stage of a beetle.

There are caterpillars, however, that resemble this insect. It is always important to get a positive ID of a pest problem before selecting a chemical or biological control. Bt will have no effect on beetle larvae.