Please refer to the images from Tall Tembers collection on the LepNet portal.
The “transparent rods” are g-strings from a guitar strung on a stand I made that included a bass string tuning peg for tightening. Worked like a champ. The background was about 5 inches below the specimen, ~10% gray. We placed the specimen on the nylon strings, which are visible, as you note. We put stickum on one portion of the strings to hold a small platform on which we placed the label (free, no stickum on the labels), placing and removing the labels with forceps or by hand (had a great tech who was skilled in arts and crafts and very steady; she also loves butterflies and is an avid enthusiast and quite expert). When we had data on both sides of the label, we displayed one side for dorsal, the other for ventral images. Otherwise, we just turned the butterfly by grasping the pin, which was never removed, and use the same label. The tech became very skilled with this. We used a Nikon D3x (would use an 810 today), Nikon 105VR macro, very sturdy Kaiser copy stand, and Kaiser florescent lighting attached to the stand and at an angle from the subject. We also, used this camera setup for our birds, mammals, and herbarium specimens, sans the specially built stand for the butterflies. We are now using this rig to image insect parts extracted from fecal pellets of quail to build a reference guide to be used during fecal pellet excavation and diet assessment (Tall Timbers works heavily on quail).