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Crossocerus
Photo#1530180
Copyright © 2018
dsacer
Wasp? -
Crossocerus
-
Palo Alto, Santa Clara County, California, USA
June 3, 2018
Size: about 3mm
Attracted to a multi-species wasp/hornet trap which uses Heptyl Butyrate, 2-Methyl-1-Butanol, and Acetic Acid
Images of this individual:
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Contributed by
dsacer
on 3 June, 2018 - 1:17pm
Last updated 22 June, 2018 - 10:02pm
This seems to have the makings for C. acanthophorus
First off (literally! ;-), at 'couplet 1' in the
Crossocerus
key for females in Leclercq
(
1
)
(2000), note that
C. acanthophorus
is immediately separated from other New World
Crossocerus
taxa by the following characters:
1) "Occipital carina complete ventrally." — I think careful scrutiny the postero-ventral edge of the oral cavity visible above the palp in the 3rd image of this series, gives encouraging partial confirmation of this character...even though the available view there may not allow verification with certainty;
2) "Mandible bidentate." — Bidentate means "two-toothed" and looking at the wasp's left mandible (which appears on the
right
in the 2nd image of the series), one can see a sharp apical "tooth" on the upper/outer tip of that mandible...and (from the ample thickness of the mandible tip) one can infer another such "tooth" blocked from view by the overlapping tip of the wasp's right mandible. (The line of sight here also blocks the view of the lower/inner tooth of the right mandible.) Note also that each mandible also has another small "tooth" near the middle of its inner edge. Leclercq indicates
C. acanthophorus
is in subgenus
Oxycrabro
, and Bohart & Menke give as a diagnostic character for that subgenus: "female mandible with a weak medial tooth on the inner margin" (see
couplet 6 here
);
3) "Collar with an antero-lateral spine." — I believe the term "collar" refers to the dorso-anterior edge of the thorax, and a small projection is clearly discernible on the upper-left anterior corner of the wasp's thorax in the image above...and also, in shadow, at the upper-right corner of the wasp's thorax in the 3rd photo. Compare those projections with the line drawing illustrating this character at upper right in
the published note here
;
4) "Mesopleuron with precoxal tubercle." — I think I see an indication of a very small, slightly-raised bump (i.e. tubercle) on the postero-ventral corner of the mesopleuron (in the 3rd photo, just forward of the miidle of the long apical spur of the mid-tibia...viewed there face-on, and thus appearing as a small circle with highlighting above, and black shadow below);
5) "Tergum II strongly depressed basally." — This seems pretty apparent from the 1st, 3rd, and 4th images...even though the edge of the juncture of the 1st and 2nd tergites is somewhat blocked/obscured from view by legs & wings and/or dim lighting;
6) "Pygidial plate: lateral margins straight, apex bare and shining." — We only have an oblique ventro-anterior view of the terminal plate in the 4th photo...but it's consistent with straight lateral margins and a glabrous pygidial plate.
If, by good forture, the specimen is still available for inspection, the above characters can be more thoroughly vetted.
Note that, in addition to the above, Leclercq indicates
C. acanthophorus
is an adventive from Europe in CA, with only two records given: one from San Jose in Santa Clara County (very near the Palo Alto locality here), and one from Los Angeles County.
Moreover, the color scheme here (i.e. nearly all black, with yellow only on: the ventral side of the scape; the anterior sides of the fore- and mid-tibiae & basitarsi; the hind "knee"; and partially on the mandible) seems fairly-well compatible with (what I can dicipher from) the
Kohl's original 1892 description (in Latin & German) of
C. acanthophorus
. Kohl also indicated the clypeus is "tridentate" medially at its apex, which I believe is discernible in the 2nd photo here. And Kohl decribed the "precoxal tubercles" as being on the sternum rather than the metapleuron, which further supports my 2nd interpretation in 4) above.
Finally, note the photos here agree well with the
3 photographs here
(scroll right with the "→" key); the 4 photos near the end of the
long page here
(scroll 9 rows up from the bottom); and the
BOLD images here
(though agreement is somewhat weaker there, due to reddish abdomen in some specimens).
…
Aaron Schusteff
, 2 August, 2019 - 9:25am
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Moved
Moved from
Squareheads
.
…
Matthias Buck
, 22 June, 2018 - 10:02pm
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Moved
Moved from
ID Request
.
…
Bob Biagi
, 3 June, 2018 - 1:53pm
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Female
6 abdominal segments = ♀
She is very dark. I wonder if the alcohol solution darkened some of her yellow body coloration.
…
Bob Biagi
, 3 June, 2018 - 1:41pm
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Dark Color
I actually caught this one just outside the trap, and then chilled it to get it to stay still. Any dark coloration is going to be an artifact of how I lit it, or something to do with being chilled.
Edit: to be clear, it did NOT have any visible yellow-and-black banding, and other similar-looking wasps which buzz around the trap do not have this banding either.
…
dsacer
, 3 June, 2018 - 5:05pm
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OK
That is good to know. She probably belongs in the genus
Crossocerus
, but a species ID may be out of reach. (...in this case) Let's wait for an expert.
…
Bob Biagi
, 3 June, 2018 - 11:00pm
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