A significant white spot on the head is, according to the Covell Field Guide, a characteristic mark of Desmia maculalis. Brian Scholtens had previously informed Bob Patterson that this is not a reliable character and that two species (D. maculalis and D. funeralis) cannot be distinguished in typical dorsal view photos. It would be necessary to see mouth parts at high magnification or examine genitalia to make specific determinations. It is best to consider photos of these species as representing a species group. More recently, he commented "The character that I use is the extent of the white patch on the underside of the abdomen. D. funeralis individuals have a solid white patch on the underside of the abdomen on segments 1-5 (or may have a slight break on segment 3). D. maculalis individuals have a broken white patch, where about 1/2 of segments 3 and 4 are clearly dark. Basically, maculalis looks striped on the underside, whereas funeralis looks like it is basically solid white."

I have used the above to sort some of the specimens I have in my collection.