I was given a dead Oregon Dark-eyed Junco Junco hyemalis oreganus today, that according to the banders who had caught it had “lots of lice” on the throat. That is usually where eggs are placed by lice, and when I looked at the bird, I found that what they had believed to be lice was actually louse eggs. Not as fun, but still something. I made a brief survey of the head, and discovered two lice of the genus Ricinus De Geer, 1778 (= Nirmus Hermann, 1804; Physostomum Nitzsch, 1818).
As I’ve never seen lice of this genus alive before (and very few dead), I decided to look at them in the dissection microscope while the bird was fumigated with ethyl acetate. I discovered something that can be seen in these short clips (my first uploads to YouTube!):
You can see the intestines working and the louse moving a bit, but the most fascinating thing is that between the legs (but a bit hard to see in the movie), there is a mite! The other louse had two mites attached to the abdomen in more or less the same spot. I’ve never seen mites cling onto lice before, and have no idea how common this is, or even if it is even reported in the literature.
The most curious thing, I think, is that the mites remained on the lice despite my manipulations of the lice first when trying to get them off the bird, and then in the tube and on the petri dishes. These seem to be feather mites, so they are probably not hypoparasites of the lice, but I can’t really think why they would want to cling to the louse at all. Surely the lice would be more prone to being preened away? Or is it because the bird was dead, and the lice are much better than the mites on spreading to new hosts?
I have no idea, and I’ll have to look into the matter further. The lice and mites are in alcohol now, but if this doesn’t make the mites fall off, we’re talking about maybe try to do some SEM pictures.
As the movie is a bit fuzzy and it can be hard to see the mite, here are some photos of the same individual.
The Ricinus species on Junco hyemalis is Ricinus fringillae De Geer, 1778, but unless I misremember, there is no recent revision of the genus (apart from Nelson, 1972, who revised the New World species).