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Photo#771897
Golden Lordotus - Lordotus - female

Golden Lordotus - Lordotus - Female
North of Lobecks Pass, Southeastern Sacramento Mountains, San Bernardino County, California, USA
March 27, 2013
This bee fly was found torpid in a flower head of Xylorhiza tortifolia, before the warmth of the morning sun energized it to begin the day's activities.

It keyed to Lordotus in the MND(1) and Cole(2)...the wing venation is fairly distinctive. As far as trying for species, I don't have access to the 1954 or 1982 Lordotus treatments of Hall (see info page), but images on BugGuide and in Lynn & Gene Monroe's recent book, "Desert Insects of Southern California & Kin"(3), lead me to suspect that this is L. pulchrissimus or L. zona...and I'm leaning towards the former. Beyond genitalic differences, these two species are distinguished by the color of their coxae: yellow for zona vs. black for pulchrissimus. But the coxae are often not visible in photos, as is the case here. Cole(2) commented that (green-colored emphasis below mine):

"L. zonus (sic) Coquillett is very common in certain areas of southern Calif.; it has also been taken in Ariz,, Nev., and Idaho. It is an autumn species in canyons of the San Bernardino Mts. of Calif. The wing is hyaline except for yellow in costal, sub-costal, and first basal cells."
On pg. 315 of Monroe(3), it's said that female L. zona are golden with white pile on the face, thorax, and femora and are active from August to November (at least in the southern California deserts), whereas L. pulchrissimus lacks the conspicuous white patches on head and "chest", and is said to be active in spring as well as fall. As this bee fly was found in the spring; has no conspicuous white patches on face or sides of thorax; and has a more-or-less hyaline costal cell (as opposed yellow, as described for "zonus" by Cole)...I'd tend to think this is probably L. pulchrissimus.

And, perhaps the BugGuide posts below (with their autumn dates, white faces, and yellow costal cells) are L. zona:



And the spring date and lack of white face on the post below might suggest L. pulchrissimus, although the costal cell looks quite yellow to me:



Then again, perhaps wide "variation" makes these characters unreliable (and perhaps these two are just a single variable species?)...I don't know, just trying to understand.

One thing is for sure, this is definitely a female...from the widely separated eyes and the golden color (sexes are often dimorphic in color in Lordotus, with males usually darker).

Images of this individual: tag all
Golden Lordotus - Lordotus - female Golden Lordotus - Lordotus - female Golden Lordotus - Lordotus - female Golden Lordotus - Lordotus - female

Moved
Moved from Lordotus.

Update...species ID narrowed to two options
Since obtaining a copy of Hall & Evenhuis(1) and studying it a bit, I've come to the tentative conclusion that this is a female of either Lordotus diplasus or L. diversus.

I arrived at that conclusion by working through the key in (1), following both leads at breaks that seemed ambiguous, and following up with a careful reading of various candidate species descriptions at each such juncture. In each case, I was able to confidantly reject the alternative choices based on characters of the resulting taxa that were not compatible with images.

The principal characters of the keying sequence are paraphrased in the abbreviated summary below:

  1b. Eyes widely separated down front (female).......................31
  31b. 3rd antennal segment without well-defined terminal style...36
  36b. Wings hyaline..............................41
  41b. Legs not entirely black, at least tibiae yellow.......51
  51b. Femora not entirely black or brown, at least apically yellow...............52
  52b. Femora entirely yellow, or at most black on less than basal half.......55
  55a. 3rd antennal segment appreciably broadened on basal half...............56
  56a. First antennal segment < 1.5 x second antennal segment, the two usually nearly equal.....diversus
  56b. 1st antennal segment at least twice 2nd antennal segment...............diplasus


Besides the final choice at couplet 56, the only other juncture at which I was hesitant was couplet 55...which is crucial, since females of the each of the subsequent taxa from the alternate lead, 55b, are all very similar. The remainder of the key from there is as follows:

  55b. 3rd antennal segment not appreciably broadened on basal 1/2, more linear in outline...........57
57a. Coxae entirely black; tomentum on mesonotum, when present, not dense........................5857b. Coxae yellow, at least at their apices, usually more; mesonotum with dense yellow tomentum......zona58a. Hypopleuron with white hair; pleura white pilose......pulchrissimus58b. Hypopleuron bare; pleura pale yellow pilose.............luteolus

If one reads the species descriptions of females in (1) for zona, pulchrissimus, luteolus, diplasus, and diversus...they are all very similar, save for the characters mentioned in the key (and quite different from the males in each species). In particular, they can all vary from pale yellow to (more commonly) golden pilose overall (with the pile long and erect), and have low, flat, similarly colored tomentum at the base of the pile, closer to the integument on the thorax and abdomen. Usually, the tomentum is denser along the medial line of the dorsum.

Regarding the crucial couplet 55, I initially had no reference for how to interpret the somewhat subjective phrase "appreciably broadened". Fortunately, I was able to find reference figures from Hull(2) showing antennae for L. diversus (Fig. 48) and L. zonus (=zona) (Fig. 46), and thus illustrating examples of "appreciably broadened" and "not appreciably broadened", respectively. Based on those figures, I believe the appropriate choice is lead 55a.

Concerning the choice at couplet 56 (i.e. whether this is diplasus or diversus), my best guess is that the 1st antennal segment is significantly longer than the 2nd. This is based on assuming the abrupt termination of the long orange-yellow pile the base of the antenna segment is close to the juncture between it and the 2nd segment (which may be wrong!). Thus I'm speculating this is L. diplasus.

It's perhaps worth mentioning that Hall first described L. diplasus as a subspecies of L. diversus in his 1954 revision of the genus, and only later was it elevated to species status in Hall & Evenhuis(1). Thus, the two taxa are quite close. The original description of L. diversus can be read online at this BHL link.

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