Re: [beemonitoring] BIML Update
- Female sandersoni should be separated by vagans by their shorter malar
spaces. Both of these species vary a great deal in color. Whatever
reliable color characters may exist are not well documented in the
literature or elsewhere and any differences may not apply throughout the
large area of overlap between these two species, the full extent of which
is not known.
The key to identifying females of these species (and other difficult
species pairs in the west) is to have sufficient familiarity with Bombus
to be able to consistently perceive the small difference in malar space
between them. This requires practice, patience, and access to correctly
determined reference material. In sandersoni the malar space resembles
that of perplexus whereas that of vagans is clearly longer approximating
that of bimaculatus.
"The amount of black on the scutum seems to vary a fair bit from specimen
to specimen, even within series"
This is certainly true. Hair color should be used with great caution when
separating similar Bombus species, as variation within a species such as
vagans likely exceeds that between vagans and sandersoni.
"these features can't be used to reliably diagnose sandersoni, at least
not the way they're phrased, without images to clarify them."
I think that's an accurate assessment of the situation. Color variation
across the ranges of both species should be assessed further before
diagnostic characters are proposed.
In my experience sandersoni queens average smaller than vagans queens, so
very large queens are likely vagans whereas smaller ones should be checked
carefully vs. sandersoni.
Doug, at many localities only vagans occurs so it is not too surprising to
see long series of that species with no sandersoni.
> Having just spent much of today going over a large assortment of B.--
> vagans, I can offer some feedback on the following:
>>Female, B. frigidus, B. sandersoni, B. vagans
>>(note, the below is somewhat controversial, so am looking for some
>>feedback...B. sandersoni is a very uncommon bee in general, but we
>>have been finding it at least somewhat regularly in the Appalachian
>>Mountains and ran into a nice string of about 50 from Mountain Lake,
>>VA thanks to Barbara Abraham's work there.
>>B. sandersoni - T1-T2 usually entirely yellow, some specimens may
>>show scattered black hairs on T2 - Hair on T4 black, but at times
>>with yellow or off-white hair on the far sides - Hair on T5 can be
>>pale yellow, off-white, black, if appearing all black there are
>>usually a few yellow hairs on the far sides - Space from lowest
>>point of eye to mid-point of attachment of mandible varies from
>>roughly equal to width of mandible at base to longer - Hair above
>>the ocelli is almost always largely black but often with scattered
>>yellow hairs - In direct comparison, the black hairs on the scutum
>>take up much of the posterior half of the scutum with yellow hairs
>>simply bordering the junction with the scutellum and near the
>>tegulae, scattered black hairs occur in these yellow areas including
>>in the anterior edge of the scutum near the head
>>B. vagans - Hair on T4-5 always black, except in Newfoundland where
>>the endemic subspecies bolsteri has T5 yellow - Space from lowest
>>point of eye to mid-point of attachment of mandible longer than
>>width of mandible at base - Face appears long, horsey - In direct
>>comparison, the black hairs on the scutum are largely restricted to
>>the center of the scutum creating only a small patch of black amidst
>>a largely yellow-haired scutum, though with scattered black hairs
>>laterally to the tegula - Hairs above the ocelli almost always with
>>extensive amounts of yellow, apparently never all black
> Looking over specimens from WV, VA, and MD, there are a few with pale
> hairs on terga other than 1-2; however, all but one of these has a
> lot of yellow on the vertex, and the malar spaces are no different
> from those of perfectly typical vagans from the same
> dates/localities. The amount of black on the scutum seems to vary a
> fair bit from specimen to specimen, even within series, and not just
> series from the Appalachians. I wouldn't say I could confidently
> classify any of the specimens at hand as sandersoni using the
> criteria you give (especially given that they otherwise are no
> different from other females in the same series) - it could be that
> there are simply no sandersoni in amongst these, but if we assume
> that, given that all of your diagnostic features (other than the
> malar space feature, though I confess to not having an ocular scale)
> appear on some of these specimens, that would mean these features
> can't be used to reliably diagnose sandersoni, at least not the way
> they're phrased, without images to clarify them.
> Doug Yanega Dept. of Entomology Entomology Research Museum
> Univ. of California, Riverside, CA 92521-0314 skype: dyanega
> phone: (951) 827-4315 (standard disclaimer: opinions are mine, not UCR's)
> "There are some enterprises in which a careful disorderliness
> is the true method" - Herman Melville, Moby Dick, Chap. 82
John S. Ascher, Ph.D.
Bee Database Project Manager
Division of Invertebrate Zoology
American Museum of Natural History
Central Park West @ 79th St.
New York, NY 10024-5192
work phone: 212-496-3447
mobile phone: 917-407-0378