Eulonchus sp.? - Eulonchus tristis

Moved

… Alice Abela, 24 February, 2016 - 11:33pm

Dr. Chris Borkent requested use of these photos and said that this fly is E. tristis.

… Alice Abela, 24 February, 2016 - 11:32pm

Candidate for species ID

Looking at these images again, it seemed a bit strange to me that a Eulonchus would be nectaring on the small, short-tubed, flowers of a Cryptantha. In my experience, both in the field and in photos, Eulonchus typically visit larger flowers with longer tubes...where their long proboscis can be put to better use in reaching nectar rewards not accessible to shorter-"shnozzed" nectar-feeding competitors.

Later, while reading Schlinger(1)(1960), I was struck by his discussion of the species E. halli, which he emphasized has a unique relationship with Cryptantha intermedia. In his observations, and those of Jack Hall and others, all but one of the 70+ paratypes observed in Riverside County were encountered exclusively on and around flowering C. intermedia...with the 1 recorded exception "trying to feed at flowers of Salvia mellifera".

Such fidelity to flowers of a single plant species was otherwise unknown in Eulonchus (at least at that time), and again...most Eulonchus visit larger flowers with longer tubes. Schlinger also remarked that the adult flight season for this species is earlier than most Eulonchus, and seems to coincide with the main flowering time of C. intermedia.

[Note: This CalFlora page indicates 3 Cryptantha species in the Burton Mesa area: clevelandii, intermedia, and micromeres...with corollas 1–2.5 mm; 3-7mm; and 0.5mm, respectively. So intermedia seems the best fit...the others having corollas too tiny!]

Putting all this together...E. halli seems a likely candidate here. Images of the type specimen look roughly similar to the post here, but with a few discrepancies. For instance, as Alice mentioned, the legs in the photos here all have a conspicuous white band on the outer basal half of the tibiae...which appears to be lacking in the type images. I'm not sure if that, and other differences lie within the range of variability for E. halli. Hopefully the revision of the genus in progress will help resolve some of these questions.

… Aaron Schusteff, 28 October, 2015 - 12:03am

Thanks for following up on this Aaron! I was lazy and just listed the common name, the plant is Cryptantha intermedia. I mentioned the plant because the flies did seem to be very faithful to it. I didn't see them nectaring from anything else. I had to spend quite a bit of time stalking the cryptantha patches before I could get some shots. There were 3-4 flies working the area. The only other Eulonchus I've seen are the less hairy, more metalic blue green species, with a really long proboscis that seems to really like bush monkeyflower (Mimulus aurantiacus).

… Alice Abela, 29 October, 2015 - 7:56pm

Moved

Moved from Small-headed Flies.

Alice, these are definitely Eulonchus, as you thought...but there are a number of undescribed species so the old references of Cole (1919) and Sabrosky (1948) probably take many distinct taxa to E. tristis.

Last I heard Chris Borkent was working (in conjunction with Ev Schlinger?) on a long-awaited revision of the genus. Hopefully that will be available in the not-to-distant future, and will be a great help in sorting out all our interesting Eulonchus posts.

… Aaron Schusteff, 23 July, 2014 - 2:29am

Eulonchus tristis

I went through the keys in both Cole (1919) and Sabrosky (1948) referenced by Aaron Schusteff in http://bugguide.net/node/view/415686/bgimage and wound up at E. tristis with both keys. Defining characteristics are black on the femora, white not restricted to knee and proboscis not extending past the abdomen.

… Alice Abela, 13 May, 2014 - 9:36pm

Moved

Moved from ID Request.

… v belov, 13 May, 2014 - 12:57pm