I have found some insects on an olive tree in my garden, I am struggling to even describe them because of the weird ... cover, cocoon, camouflaged tube they live in. The insect is small, about 5mm and blackish, the tube is made of a soft, but quite strong green substance, it is conical in shape, with the head of the insect at the open end, attached and presumable feeding on the tree. The tree has a fair amount of green algae on, and the conical tube is the same colour exactly. The cone shapes are in clusters of 3 or 4, and around them are loads of tiny creatures resembling spider mites.
The larva looks like those of chrysomelid beetles. There are some chrysomelids which have case bearing larvae so I wonder if it could be one of those. See -
This is just a suggestion. Hopefully someone will contribute a firm identification.
I'm thinking that it may also be worth considering the Psychidae family of micro-moths, also known as bagworms.Their larvae, in a similar way to caddisfliy larvae, live inside cases made from various fragments of material. These vary in appearance among the species, of which there are 20 in UK. I've seen one or two before but don't know my way around them to make even a shaky id.
This might help: http://www.ukmoths.org.uk/search.php?entry=psychidae
That definitely looks more like it, and the olive tree does have algae and lichen on it, however none of them look exactly right.
Another factor that is troubling me are the tiny 'mites' that are in the same areas as the cased insects, they really do resemble red spider mites - minute black/brown and round - moving, so definitely not eggs, and both are in exactly the same locations on the tree, I cannot understand how they can be connected, but it seems a strange coincidence.