Parasitized greedy scale
Parasitized greedy scale insect. Note the hole in the center of the insects armored covering. Parasitism is good news! It means we have beneficial insects out there, and they're doing good work!
What's it caused by? Parasitoid insects (often tiny wasps the size of sugar ants) will lay their eggs in the scale insect. The eggs hatch and the larvae eat the scale insect before emerging through its outer covering. Ever see the movie "Alien?" Well, you get the idea.