Pliny's account of the Qumran group (if it were a single group) is so wrong that it cannot be said to have been written by someone who had witnessed them. I suspect that he had read Josephus and more likely Philo, and added whatever commentary he based on anecdotal experience or conjecture. He was a magnificent blow-hard, and records of his extremely expensive ego are of great value and speculation:

Pliny the Elder, Natural History 6. 195 : "Then come regions that are purely imaginary : towards the west are . . . the Cynamolgi, who have dogs' heads."

Josephus' account of the Qumran group is decidedly politicized. The destruction of Israel - and Judaism - was Josephus' chosen life (though he hadn't great options to choose from). Tiny details, such as displaced Temple Priests descended from Zadok, and some guys named John The Baptist and Jesus The Christ making a bit of a fuss, were not afforded much if any detail, interest, or importance within his accounts. 

Philo is the earliest extant record of the Qumran sect being called the "Essenes":

EGMIF - Chapter XII. (75) ... There is a portion of those people called Essenes, in number something more than four thousand in my opinion, who derive their name from their piety, though not according to any accurate form of the Grecian dialect, because they are above all men devoted to the service of God, not sacrificing living animals, but studying rather to preserve their own minds in a state of holiness and purity.... (91) and yet no one... ...was ever able to bring any real accusation against the multitude of those called Essenes or Holy. 

Philo appears to reveal - if not be - the origin of the misnaming of the sect.  The confusion came from misinterpretations of Greek language.

They were considered "The Holy", and would not have argued against that characterization. 

"Holy" is "hosion" or "osion", and the term "Essene" is neither a long stretch phonetically (o-sion vs ess-ene, osioµn vs essaioµn), nor is the general appearance and function different between the the displaced priests and other priests with a similar name.

https://biblehub.com/greek/3741.htm

The Qumran group did not identify themselves as "Essenes", and the word "Essene" cannot be found anywhere within their archaeological record. 

At all.  

Ever.

Not once.

Actual "Essenes" were priests from - and descended from - the Temple Of Artemis, who had very little in common with the people at Qumran, except their wardrobe.

The Qumran group rarely expressed themselves as apart from Israel-proper, except to account for themselves as "haChitsonim" - "The Outsiders".