Wednesday, August 30, 2017

News Bee

Yellowjacket hover fly, Milesia virginiensis - REK
There are a lot of yellow flies on the flowers now.  These are Syrphidea family members, aka. hover fly, flower fly, or syrphid fly.  At first glance they are confused with yellowjacket wasps but there are significant differences in shape, size and flight pattern. 

Syrphid flies hover around flowers before landing to feed on nectar and pollen.  They look dangerous but they have no bite or sting and are entirely harmless.  Not so with their larvae which are predators on garden pests like aphids, scale insects and thrips.  They can destroy hundreds of aphids overnight, and when lady beetle populations are low they become the dominate predator.

My favorite is the yellowjacket hover fly, Milesia virginiensis, seen above. It is a noisy creature and its sound and pattern is distinctive enough that I don't usually even look to identify it. At first glance its hornet body shape and loud buzzing are threatening, a great example of Batesian mimicry to avoid predators, but watch it closely and it just wants to be friends.  It is a very friendly and curious insect that seems to enjoy human companionship.  It's known as the "news bee" for its habit of hovering relatively close to your face as though it was delivering the latest gossip.  No other insect does this and its behavior is as distinctive as its markings.  It is said that it's good luck if one can get the insect to perch on a finger.*  Given their sound and appearance, it is more a mark of bravery.

M. vrginiensis has a stalking behavior in mating.  The male hangs around flowers in the morning looking for females, then moves to areas where the females lay their eggs later in the day.  For those wanting to take a stab at insect identification, has this description that you can compare with the pictures.
"Traits of the adult to watch for include: a completely yellow face; yellow to light brown antennae; yellow femora and tibiae, with the tarsi somewhat darker. Wings cloudy but unpatterned, typically darker at the apical end."
Sphecomyia vittata female - REK
Many other flower flies mimic yellowjackets, possibly because of their aggressive traits and unpredictable gang warfare.  This one wasn't hovering as usual and when I compared the markings it was a close mimic of M. virginiensis.  It fits many of the features described above but the thorax and abdominal markings are far different.  This is why amateur entomology is fun!

Toxomerus marginatus male - ID by James Trager
This specimen was obviously quite different.  I was lazy that day and sent it off to Bi-State Bugs where James Trager IDd it as a male Toxomerus marginatus.  It took me a while to discover how he could identify it as a male.  It turns out that the eyes have it.  The males have bigger eyes - they have to find the females who are hanging out in a flower bar, just waiting to be picked up.  The guys have to be able to tell the difference in sexes to avoid wasted time and embarrassing encounters.
"Like all other flies the males have bigger eyes which come closer together at the top of the head. Females have much smaller eyes, placed farther apart. Tiny eyes or ocelli are composed of single cells and are found at the top of the head in a triangle between the large compound eyes."
Now with your new-found knowledge about sexing (not sexting) a hover fly, you can see that this specimen I photographed was a female.  You are now off on your way to being an entomologist!  Just a few more years to go, but a warning.....It can be addictive.
* Kaufman Field Guide to Insects of North America

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