Pest on my Leyland Cypress
These look like ladybeetle larvae--beneficial insects! http://treefruit.wsu.edu/crop-protection/opm/lady-beetles/
I don't think they are causing your problem. My guess is that they have found a pest to eat on your trees. Aphids, mealybugs and scale insects all feed on the juices found within the Leyland cypress foliage, stems and twigs. Aphids and scale insects tend to feed in colonies. Aphids and scale insects also exude a sticky substance known as honeydew that attracts ants and provides a growth medium for sooty mold. Lady beetles and their larvae will come to dine on them.
I can't see what's going on in your photos, but please take a look at where I've marked on your photo. Get a magnifying glass to see if you can see them better. I can't tell if I'm seeing scale insects or aphids. Please get back to me.
Also how do you irrigate them in your long, dry summers up there?