Velvety tree ants, Liometopum occidentale, infesting a ceiling

We had an unusual occurrence of velvety tree ants infesting a ceiling, inside a home, in the Sonora area. I have seen this type of infestation in the past, but it is rare, and we were able to document this case. Most commonly, it is pine tree ants, Liometopum luctuosum, that we see exhibiting this “nesting in the ceiling” behavior. But this one was velvety tree ants (confirmed by Dr. Philip Ward), and the velvety tree ants were there in large numbers.

Ron Walther reported that the ants were in the open beam ceiling, and were dropping larvae down onto the sofa and floor beneath.

After the application by technician Erik Brians, there were piles of dead and dying ants.