Wednesday, May 5, 2021

When is a Bumble Bee not a Bumble Bee?


Hover like an indecisive bee, buzz like a bee if not louder, look just like a bumblebee; must be a bumble bee right? When is a Bumble Bee not a Bumble Bee?


While photographing bumblebees in our backyard I captured photos of this, which at first, before viewing the photo, appeared to be a common eastern Bumblebee,  Bombus Impatiens

And in fact, that is what nature or evolution appears to have intended, as this is a Criorhina nigentris, (Bare-cheeked Bumble Fly) a mimic of an eastern Bombus (bumblebee.) 

While most insects have four wings, flies have only two. Syrphids usually have large heads, large eyes, and short antennae. Skevington & Locke

Bare-cheeked Bumble Fly  

Criorhina nigriventris

Click on the link above for iNaturalist post. 


According to The Field Guide to the Flower Flies of Northeastern North America, Skevington & Locke,  flies carry out about one-third of our pollination services


Among the flies, syrphids are usually the most important. The larvae of many of them are predators of aphids and other pests, some recycle sewage, some are bacterial filter feeders in sap runs.  Skevington & Locke

The Field Guide covers 413 species of flower flies (syrphid), also known as hover flies, while there are 6,300 species known in the world. The species shown here is listed as uncommon. 



According to Skevington & Locke, most adult syrphids mimic wasps or bees in some way, and some are perfect mimicry, looking and behaving almost exactly the same as their models as is the case in this specimen I was fortunate to observe. Some flower flies have different color morphs to match the morphs of the bumblebees they are mimicking. 

Note: No syrphids bite or sting!



So much to discover in our backyards! We look for life in the stars while our own yards are immensely underexplored for the countless species that live there. 


Bernie
Observing life in nature.
Connecting native habitat, wildlife, and community.

Guest post by Don Miller, 
field-oriented ecologist/zoologist and naturalist.

Mimics

Many species of syrphidae: so-called flower flies or hover flies mimic bees and wasps as does the wonderful example that Bernie has recently shared.  Many are not merely almost exact color mimics of a specific species of bee or wasp but some exhibit other patterns of mimicry, such as acoustic or other behavioral patterns.  Some species of flower flies extend their front legs forward and waggle them the same as some stinging wasps.   The above are generally referred to as perfect mimics. 


However, many other species of flower flies seem to have a general appearance or a gestalt of a bee or a wasp if you will.  This has raised some questions as to whether it is classic mimicry at all or if so, how does it function.  In other words, how is that general resemblance maintained in an evolutionary sense? And then, given a large number of species of flower flies, it is not surprising to learn that many species don't resemble bees or wasps at all, at least to the human observer.  These are almost inevitably overlooked in general surveys. 


I  noticed the phenomenon of mimicry perhaps 50 yrs ago, especially in the Victory Bog WMA when I was first becoming aware of syrphids and how many were incredible mimics, to the point of completely fooling me. 


For example, when I first handled with great trepidation what I thought was a stinging hymenopteran, I soon learned that not only is mimicry based on shape, pilosity, and color patterns but with many some mimics there is a distinct behavioral difference.  I learned that some of the mimics buzz like a bee much more loudly than the real thing. In fact and somewhat paradoxically, this was often the tip-off that I could safely touch the individual without fear of being stung. 


One might even think this could be counter selective because a predator of the harmless fly, might learn that indeed by its extraordinary louder buzzing, in fact, it is not a bee or wasp. One knows that one can cry wolf just so many times if no wolf is present before the shout is ignored.  At what evolutionary stage does the loudly protesting mimic have to change its behavior?  Certainly, not all hover fly mimics are not acoustic mimics of the buzzing of bees say. Why is that the situation? 


The phenomenon of mimicry in flower flies is just one example of how little we know about them as a group. And the evolutionary significance of the variety of mimicry patterns in the animal worlds has been studies and dated for decades by scientists.  Syrphidae represent an ideal group to clarify many of these perennial questions about mimicry as a general biological pattern in many animal-and even plant groups.  And this area of research is now a very active one with the syrphidae.  Why does man do this? Well, supposedly he wishes to understand as completely as possible the world that he shares with other organisms. Paradoxically, we are still living on a very mysterious planet, despite what many may think. 


They are an extraordinary diverse major family of insects with many major differences in their biology. In general, they impact ecosystem functioning and services in many ways, and we know little about most of these. In fact, new species of flower flies are still being discovered here in N. America every year, even in this general area. We hardly know anything about the ecology of most.  In fact, we don't even know how many species there are in Vermont except at a very general level of documentation. 


Citizen scientists could greatly help in documenting the number of genera and even many species in the State, by simply taking very good photographs of actual or suspected flower flies in their gardens or other habitats around their property. 


If possible photographs should include frontal, lateral, and top or dorsal aspects. of individual flies. Most naturalists take the latter which is generally good enough for identifying an individual to genus by even non-specialists who have the Skevington et al Field Guide. In fact, I would encourage simply photographing any insect following the criteria mentioned here, not just those thought to be flower flies. Better to err, than to miss documenting a genus of flower fly previously unknown in the State  Keep in mind that some species of flower flies do not regularly visit flowers or never do. Look for them on stumps in the woods and places like that, as well. 


Don Miller

-------------------------------------------------------------------------------------------------

View more about Syrphid Flies (flower flies) from the U.S. Forest Service at https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/syrphid-fly.shtml


See earlier posting of 5 species of BumbleBees I recorded at https://jerichovermont.blogspot.com/2021/04/observe-and-know-life-in-your-yard.html

Bernie

No comments:

Post a Comment