You stimulated an interesting question for me: What might the rate of dispersal be for a population as potentially mobile as a fly like Eulonchus? Don't know how long adult E. sierraensis live, but as I recall larvae in the genus are parasitoids of spiders, and adults presumably subsist on nectar. So assuming there's a viable habitat corridor, I wonder how many generations it might it take for E. sierraensis to cross from the south end of the Sierra to the west end of the San Emigdios? Perhaps not very long (provided they know to fly high over I-5!:-).

PS: I be interested in a Eulonchus revision for the West too. Fascinating genus...and there's at least one more from the Siskyous I'd enjoy keying. Please keep me posted :-)

Another possibility would be Eulonchus halli making its way east from the San Gabriel Mtns. You're seeing them in an interesting area where southern and northern species meet, along with influences from the coastal region.

for this specimen. That species seems to be more restrictive in distribution than I originally thought. It also appears to be strongly adapted to utilizing a single floral host and habitat in the general region of Riverside, CA.

Flies can be surprising and we always underestimate their dispersal abilities. So I am not sure if they would need generations!
It looks like Ev Schlinger has a manuscripte about this genus, but I would be extremely surprised if he ever publishes it (although I would be extremely happy about this)..
Cheers
Martim

Guess so...maybe just need a single fertilized female to fly or get blown over there.

Would circulating a letter of support and encouragement from friendly fly folks help motivate Ev Schlinger to disseminate the document...it might make for more euphoric Eulonchus enthusiasts!

The possibility is quite high that the Eulonchus you see in western Kern County are the same. Its also possible that through allopatric isolation they have adapted and changed sufficiently to be a different taxa. Mt Pinos is an extension of the Sierran floral and fauna and that's just a hop-skip-jump away.

As to Ev, we've talked about this, but his focus over the years has been more on the worldwide fauna than those in his own backyard. He's notorius for not returning loaned material and not letting people know just what they have sent. He's a fount of knowledge on the group, but I fear much will be lost when he passes. He has hundreds of my specimens that I will never see again :-( I love his enthusiasm and knowledge, and if you can get him to sit down and talk about small-headed flies he'll make you want to run out and find them, but.... none of us are perfect.

That is so true what you wrote about Ev. I always hope that later on somebody will be able to work up the Western Acrocerids. They are too cool not to be known. So maybe there is a project for you in the future.

Ev is 79 and seems to be going strong, though recent legal and financial problems may slow him down a bit. He always said he wanted to save the local flies for the time when he couldn't travel the world. "We" gave a paper on the diversity and activity periods for Acroceridae in Tulare to the ESA in the 80's, but I couldn't get more than the title from him. Never saw a copy of "our" paper. I did all the field work and he identified the specimens and wrote the paper. I couldn't even get a list out him for donation purposes. Oh well!