This individual was found on an inflorescence of Nolina parryi
. The inflorescence stalk (shown here
) was over a meter long, and had a constant contingent of honey bees (Apis mellifera
) foraging on it. The conopid landed and flew off several times during the 20 or so minutes I was observing, though I never saw it make contact with a bee.
This is clearly Dalmannia
, and the species ID can be narrowed to either D. blaisdelli
or D. picta
and Camras & Hurd(1)
(1957). The maps in Camras & Hurd indicate the ranges of these species largely overlap, in particular throughout nearly all of (the west-of-the-deserts portion of) California.
However, despite careful study of those two references, and:
For D. blaisdelli: Cresson's original 1919 description, and images here and here; andFor D. picta: Williston's original 1883 description, and images here and here
...as well as study of specimens at the Essig Museum...I'm unable to unequivocally place this conopid to species.
Part of the problem lies in the difficulty of clearly discerning the color and length of the thoracic pile in most photos. Even with a microscope, rotating a specimen often makes black hairs look white and vice-versa...due to shadowing vs. glisten when the angle of view is changed...making it hard to tell the true color. But a more insuperable difficulty arises in certain ambiguities & inconsistencies between the written characterizations given for these two species (in the keys, descriptions, and discussions from the literature cited above) and the actual characters manifested in the individual here as well as in specimens I examined from the Essig Museum collection.
The key couplet separating the two species in Camras & Hurd(1957) is:
Pile of dorsum of thorax predominantly pale............pictaPile of dorsum of thorax predominantly black in the center, yellow anteriorly............blaisdelli
Also, the wings of blaisdelli
are described as typically "smoky"; whereas in picta
"the wings are never smoky". Since the wings appear smoky here, that would seem to eliminate picta
However, Camras & Hurd also state that in blaisdelli
: "The anterior pile of the thorax is always yellow if not golden in color." But the anterior thoracic pile in my photos does not appear yellow...it appears either black (in 1st–3rd images), or whitish (6th image), or a mix of the two. So that would seem to eliminate blaisdelli
I found similar inconsistencies with curated specimens at the Essig Museum (some determined by Camras himself, who coauthored the 1957 bulletin (1)
under the auspices of UC Berkeley and left specimens in the Essig collection).
In fact, in their remarks on picta
, Camras & Hurd state: "This species is more variable than previously considered and intergrades completely with blaisdelli
." All this makes me wonder whether these two taxa may just be variations within a single biological species.
But there is apparently another character of relevance...namely, the length of the thoracic pile. The key in Bohart(1948) indicates picta
has: "hairs of dorsum of thorax averaging shorter than length of arista"; while for blaisdelli
they are "distinctly
shorter than arista". This seems consistent with Jeff Skevington's comment
that in the CNC collection, the picta
specimens he reviewed had significantly longer (and paler) thoracic pile than the blaisdelli
specimens...as illustrated by the images of male picta
posted by Jeff Skevington's student, Trevor Burt
...perhaps selected from the same collection Jeff had viewed?. Taking this into account, I'd say my post here looks more like blaisdelli
One last item of interest: I think this is a female, even though there's no clear view of the characteristic forward-curled, elongate tip of the female Dalmannia
abdomen here. Appears it's almost entirely blocked by the hind femora in each of the views I captured...which seems to often happen in female Dalmannia
photos. But, though hard to make out, the knife-like tip of this female's abdomen can barely be made out in the 6th image. And I think I can also see (appressed against the 2nd & 3rd sternites) a black sliver of the "forward-bent, abdominal tip" in the 3rd & 4th images of this series. In support of this claim, note that the 6th image indicates the venter is yellow out to at least the 4th sternite...so those black "slivers" under the abdomen in the 3rd & 4th images aren't the sterna, but are the barely visible portion of the elongate female abdominal tip.
More support for this being a female comes from the descriptions of sexually dimorphic femora coloration given by Cresson and (indirectly) Williston. Cresson described the femora of female blaisdelli
as: yellow, with fore-femora black above, and hind-femora with a black apical band. That fits my post here (and my previous post from Santa Clara County) exactly. Williston described the femora of female picta
similarly. Cresson described the femora of male blaisdelli
as "black, except the broad apices", and while Williston only decribed the female of picta
(from only one specimen!) he speculated that, like D. nigriceps
, the leg coloration would exhibit sexual dimorphism...with males having more black on the legs. This seems to be borne out in the two male images posted by Trevor Burt, and the males appearing in the BOLD images here
. A comment by Joel Gibson
observed that leg color appears to be variable in D. picta/blaisdelli
...but perhaps Joel was not aware of the info in Willsiton and Cresson's (somewhat obscure) original descriptions (which may not have been accessible via BHL links back in 2011). Perhaps most the apparent variability may be explained by different (but fairly coherent) leg color patterns for males and females?