Lou Sorkin (of the American Museum of Natural History) has generously shared the following new image with us. He describes it as,
. . . 2 bugs in a small box, 1/4 inch graph paper. Male & female just fed and mated 48 hours prior to picture. Sometimes both are together, sometimes apart. Here (in close-up) the female had already laid an egg which can occur 24 hours after mating. Unfortunately, I hadn’t looked at the box after first 24 hours. Fecal spot is pale because first digested fluid must be the plasma portion of the blood. This bug hadn’t eaten for months. I think if a bug had already consumed blood within a few days of feeding again, the remaining blood in the gut would be primarily red blood cells, so a newly fed bug that had digested blood in the gut would defecate out the dark, digested blood first, hence dark spotting from what appears to be a recently fed bug. Although if a bug feeds and fills to capacity, possibly a large amount of feces quickly ejected could be a dark mixture but I haven’t looked at this yet. I’ve seen posted bed bug movies where the ejected liquid is dark, but I don’t know if the bug that had been feeding had been starved for months and the gut is empty or it had recently fed within a few days time.
Image copyright: All Rights Reserved, Dr. Louis Sorkin.
Note: you can see the original here.