Well, I like people who like people who use "correcto" and I also really appreciate them when they confirm a diagnosis.
I love robber flies, especially these big bumblebee mimics. And I don't trust ANY bumblebee to be what it seems unless it's actually buzzing from flower to flower or crawling into a hole in the ground.

Well, I like people who use the word 'correcto.' But this does appear to be L. thoracia. Though that is a major amount of yellow on the first several abdominal segments even for a female. The only possible imitator is the little known L nigella and I doubt it occurs in Illinois. It think that black facial hair and the orangy legs are pretty good keys to thoracica.