Entomology (Study of Bugs)/Mystery bug
I live in San Diego, CA. My son has been getting bit by these bugs that I have found hiding behind things in his room. He gets bit at night when he goes to bed. I've smoothed them before and I can see the blood they had in their belly. It has a round rear end and thin brown head and neck, six legs, looks similar to an assassin bug but about the size of an ant. I need to get rid of these things ASAP, my son doesn't even want to sleep on his room anymore. The last bites he got swelled up and got hard. I took a picture of one before I killed it, which I have attached for you. This one was hiding behind a sweater hanging on the wall. Please help!
This appears to be an early instar (stage) of the kissing bug (closely related to assassin bugs). Since some of these can transmit diseases such as Chagas Disease it would be a good idea to have it examined by a specialist with access to a microscope. If you contact your local Cooperative Extension office (www.extension.org) they will help you get in touch with the university folks.
In terms of control your best option is to thoroughly clean with a vacuum cleaner. Insecticides won't be very effective and can be messy. You may need an on-site inspection (again through Extension) to figure out how the bugs are entering the house. If your son has rodent pets in the room these should be removed since rodents can be host to the bugs.
Post a follow up if you have questions.