Hannah Stormer, my previous M.Sc. student and now lab tech, has been mounting mites and lice from Brown-headed Cowbirds (Molothrus ater). Among hundreds of Proctophyllodes, Amerodectes, Analges, Mesalgoides, Strelkoviacarus and other feather mites was this single specimen of a very small (~150 microns in body length), strange-looking larva:
Legs I and II have long ambulacral stalks, and there are rows of jagged denticles on its dorsum.
The denticles are reminiscent of the dorsal integument of sarcoptid mites (e.g., Sarcoptes scabiei), but sarcoptids are restricted to mammals. Had the cowbird accidentally acquired a mange mite from a cow that it had perched on? That would be odd but not impossible. On the other hand, birds do have their own types of ‘mange’ mites from a different family. Scaly-leg mites in the epidermoptid subfamily Knemidokoptinae* can cause crusty growths on the legs and around the beaks of their hosts. But all the knemidokoptines that I’ve seen have been adult females, which have very stubby legs and lack dorsal denticles. The images below show the foot of an afflicted grosbeak and a female Knemidokoptes** from its scabby toes.
So, I scoured my med-vet entomology texts and Google-Scholared in search of illustrations of larval knemidocoptines. After much searching I had found only blurry photos and a solitary drawing of the amulacral stalk of a Knemidokoptes larva. But the stalk was long and thin, like that of the mite Hannah had mounted. At that point I decided it was time to ask someone who would know whether it was a stray sarcoptid: Hans Klompen from Ohio State University, whose Ph.D. thesis was on phylogenetic relationships within the Sarcoptidae. I sent Hans some photos and quickly heard back from him that (a) it was not a sarcoptid larva and (b) that he recognized it as a larval Knemidokoptes – hurrah! I hope that this post will help others avoid taxonomic frustration should they also come across these odd little mites.
*Previously a separate family, Knemidokoptidae.
**Also spelled as Knemidocoptes and Cnemidocoptes in the literature. GBIF indicates that the ‘-koptes’ spelling is the senior synonym.
(top two photos by Hannah Stormer, bottom two by Heather Proctor)
The Inquisitive Anystid 