7105.      They appear outside my backyard, around my backyard door, on the brick wall of my house. After I step on them, a patch of red blood spread. First time seeing them after few days of rain, I have not seen them before. People mentioned seeing them lately around 10km away from my home. What are they? Are they harmful? Why they are red-blooded?

Number 7105. This is an aphid (Hemiptera/Sternorrhyncha: Aphididae). The red you noted came from the aphids’ tissues and is not blood. These strictly are plant feeders; some species can vector viral diseases of plants. Click here for more detailed information