What is this on the katydid?
Unfortunately, I cannot identify what the objective is that was attached to the katydid. There is a possibility that the insect has a disease such as a fungus or it had been injured by something and the blob was the result of the injury.
Was the katydid appearing to be "sick"?
Once we removed it the katydid seemed to try to go after it. The katydid was impaired originally because its eyes were covered by the "thing". Once removed the katydid seemed fine.
Very bizarre! Unfortunately, I have no answer as to what it is or was. I could find no reference to any like it. Sorry I can be of no additional help.