Beaver Beetles

Posted by David Moskowitz on July 27, 2010 at 8:52 AM

At long last after about a three year hunt I was able to secure some beaver beetles! I had put a call out to the beaver trapping community and finally this January I received a call that one of the trappers had obtained 9 beetles from an adult beaver trapped in a lake near Hyper Humus (Newton) in Sussex County, New Jersey. This is the first record of the ectoparasitic beaver beetle from New Jersey. These small wingless and eyeless beetles live on beaver and feed on the beaver's dead skin. They are flattened and at first glance look an awful lot like a flea. The scientific name is Platypsyllus castoris. They have previously been recorded from neighboring states but not New Jersey. An excellent reference on their ecology and distribution is at:

Here are a few photos of these amazing beetles I took through a microscope (they are only about 2-3mm in size):

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Reply Liti
9:21 AM on July 27, 2010 
what other amazing insects live in our state waiting to be discovered? get to work, Dave!
Reply David Moskowitz
10:08 AM on July 27, 2010 
Hi Liti...funny you should say that. My colleague recently discovered a small cicada in north Jersey that has not previously been recorded in New Jersey and we are currently writing up the report for publication. The species is Okangana rimosa.
Reply Richard Wolfert
10:26 AM on July 27, 2010 
Fascinating, and well done. Their form of locomotion is not readily apparent and it would seem that their legs (short??) are beneath them.

If beavers are present in the state, why have these not been ID'd in NJ before?
Reply David Moskowitz
10:41 AM on July 27, 2010 
Without a doubt beaver beetles are more widespread and common then the literature reflects. I think it is simply one of those things where there aren't a lot of people looking for ecotoparasites on beavers (what a surprise!). Of interest though, is that in New Jersey as in most of the northeast, beavers were basically extirpated by hunting in the early 1800's. The last reports of wild beavers in New Jersey prior to their reintroduction in the mid 1900's was from around 1820 or so. In the 1907 Annual Report of the NJ State Museum, beaver is noted as" nearly extinct everywhere, and according to Mr. Rhoads, the last New Jersey specimens were killed about 1820." Beaver remained very uncommon in New Jersey until fairly recently and that may have impacted the collection of beaver beetles as well. In any case, a very interesting and highly evolved beetle that is believed to be related to fungus eating beetles that likely entered the beaver dens on beaver collected wood and then evolved to feed on the beaver itself.
Reply york
10:24 PM on November 15, 2010 
just trappedsome beaver in Utah found hordes of these on them so if anyone wants any give me a buzz