[Pollinator] Fwd: Pepsis wasp pics

[Peter Bernhardt]

About two weeks ago we caught a large, Pepsis wasp while it foraged for
nectar on swamp milkweed (Asclepius incarnata) at the Shaw Nature Reserve.
As you know, milkweeds release their pollen as discrete pollinaria although
the structure and anatomy of pollinaria in the Asclepiadaceae differs from
those made by orchids.  A milkweed flower has 5 stamens so a flower should
make 10 pollinia arranged in 5 pollinarium units. This morning I gave the
wasp to Dr Camilo to take a photo of the pollinarium.  As you can see,
there were really two pollinaria (each pollinarium has 2 polllinia)
 attached to one lobe of the wasp's tongue.

Pepsis wasps are very common at the Shaw wetland site where this milkweed
grows but we've only seen them on these flowers a few times and caught only
two females.  They seem to prefer the shallow, compact florets of various
members of the aster and goldenrod family (Asteraceae).  The second wasp
caught on the milkweed carried no pollinaria.  There's nothing unusual
about finding milkweed pollinaria on the mouthparts of certain foragers but
you are much more likely to find them on the proboscides of large apids
especially Apis, Bombus and Xylocopa.  The primary pollinator of this
milkweed at this site appear to be females of carpenter bees (C.
virginiana).

Peter


------- Forwarded message ----------
From: Gerardo Camilo <camilogr at slu.edu>
Date: Mon, Aug 22, 2016 at 11:35 AM
Subject: Pepsis wasp pics
To: Peter Bernhardt <bernhap2 at slu.edu>




-- 
Gerardo R Camilo, Ph.D.
Assoc. Professor of Biology
Bioinformatics and Computational Biology
   & International Studies
Conservation Fellow, St. Louis Zoo
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