Monday, May 5, 2014

Say what you see

Identifying insects can be hard, but sometimes it can be as simple as playing the game "say what you see".  Can you guess the name of the munching (not munched-on) bug in the picture below?

A bee assassin eating a euminid wasp on prairie parsley.

It's called a 'bee-assassin' (Apiomerus crassipes), and it's feeding on a euminid wasp (Symmorphus? Euodynerus?) that landed on the wrong prairie parsley (Polytaenia nuttallii). 

Bee assassins lurk under flowers, waiting for passing bees and wasps. When a bee or wasp alights on the flower, they grab them with their sticky forelimbs. Then, like spiders, they inject their saliva and slurp out their victim's liquefied insides.  Another interesting note- bee assassins don't have naturally sticky legs. They gather the resins they use to catch their prey from plants.

Assassin bugs (Reduviidae family) are generally noted as beneficial insects in the garden.  They can have a voracious appetite for garden pests.  Bee assassins themselves, despite their relation to such handy bugs, don't tend to specifically serve a beneficial (from an anthropocentric perspective) role. However, they are opportunistic hunters. While they have fine-tuned their hunting style to capture pollen and nectar feeders, they'll snatch anything they can reach.

Both bee assassins and euminid wasps are considered 'beneficial insects', so whom should we root for in this case?  I think most people would root for the bee assassin- our collective aversion to wasps is outsized relative to their capacity for harm. Even though I find wasps fascinating and don't fear them, I still startle when I hear one buzz my ear.  This is an unfortunate reflex. Wasps are excellent garden defenders. Euminid wasps carefully provision each of their eggs with a pesty insect snack. They are known predators of caterpillars and grubs.

I observed another example of "say what you see" a few feet over in the same parsley patch. I caught a glimpse of this fuzzy, buzzing flier out of the corner of my eye and stepped over to get a look.

bee-like flower scarab (Trichiotinus piger)

I was hoping for a bumble, but this odd-looking beetle did not disappoint. Adult bee-like flower scarabs feed on pollen, while the young are ground-dwelling grubs that feed on the roots of graminoid plants. According to the Xerces Society's book "Attracting Native Pollinators", these beetles are important for magnolia pollination.  Magnolia flowers evolved before the time of bees and butterflies, so to this day they are primarily pollinated by beetles.

I'd love to know why bee-like flower scarabs are so fuzzy. Is it to mimic bees and avoid predation? Is it to collect pollen? For now, I'll have to live with the mystery.

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