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1449Re: [beemonitoring] Bee collecting cactus spines? [1 Attachment]

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  • Peter Bernhardt
    Apr 5, 2011
      Dear Chanda:

      I can't identify the bee but I can say I don't believe it was collecting cactus spines or the detachable barbed hairs (glochidia).  It is obvious that the bee is foraging at the spine cushion (areole) of an Opuntia (prickly pear)... right?  

      Did you know that the spine cushions of some opuntias secrete extra-floral nectar?  This secretion tends to be associated with new growth and I find it most easy to see when the pad enlarges and produces cushions that still have their short-lived, fleshy green leaves.  In fact, in some Opuntia spp. the short-lived, fleshy leaf appears to secrete nectar from its stomates.  If nothing drinks the nectar it may crystallize into a whitish pin head (sweet to the taste).

      What's the function of this sugary fluid?  Purportedly, it attracts aggressive ants and some parasitoid wasps.  They consume the nectar but keep the new growth free of chewing and sucking pests.  Extra-floral glands are also very common on the flat, leaf-like branches (phyllodes) of Australian acacias.  I collected insects on these glands years ago and published a paper on how predatory wasps were more common at the glands than  true bees.  Irene Baker's analyses of the secretions turned up all sorts of nutrients including sugars and amino acids.  


      On Tue, Apr 5, 2011 at 8:47 AM, Chanda Henne <csbutrfly12@...> wrote:
      [Attachment(s) from Chanda Henne included below]

      Hi all,

      I was out recently to take pictures of bees in the open prickly pear cactus flowers, and noted a bee spending a lot of time around the spines.  At first I thought it was a halictid due to its blue-green color, but after examining the photos, I am not so sure anymore.  My next thought was Osmia, but am a little confused by the behavior.  I know some bees will collect other plant parts for nesting, but I didn't think Osmia was one of those groups.  I have attached a picture of this bee, and was wondering if someone might recognize it and/or explain the behavior.  The picture was taken at the Arroyo Colorado birding center park in Harlingen, TX.


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