Bumblebee Mimics

by Carl Strang

There are mimics, and there are mimics. A couple years ago at Mayslake Forest Preserve I found a syrphid fly that mimics bumblebees.

This is the narcissus bulb fly, Merodon equestris.

This is the narcissus bulb fly, Merodon equestris.

It was comparable in size to a small worker bumblebee, though none of our local bumblebee species match this color pattern, and it doesn’t really pass for more than a few seconds’ examination.

But there are others, like the one I saw yesterday:

This is more like it. It’s big, the size of a bumblebee queen, and it’s hairy, and its color pattern resembles those of a couple local species.

This is more like it. It’s big, the size of a bumblebee queen, and it’s hairy, and its color pattern resembles those of a couple local species.

This is a robber fly, a predator known to catch bees as well as other relatively large flying insect prey. There are a couple species in the East which are very similar to one another. Their larvae tunnel in rotten logs, preying even then on other larvae they encounter. After maturing, they perch in sun flecks on leaves or on more solid perches. The more common one in DuPage County appears to be Laphria thoracica.

Here’s another individual I photographed in July 2008 at Danada Forest Preserve.

Here’s another individual I photographed in July 2008 at Danada Forest Preserve.

Note the long black hairs on the top, front and sides of the head. If those were a dense solid yellow this would be a different species, Laphria grossa. I encountered those in south central Pennsylvania, and the impression was much the same. That beak probably could deliver a nasty bite if you grabbed this critter, but why would you want to? These take a longer, closer look to distinguish them from bumblebees. That beak is one giveaway. Another is the single pair of wings rather than two. Also, the perched fly frequently snaps its head to different angles, tracking possible prey. Bumblebees don’t do that. These robber flies are on my short list of niftiest local mimics.

Why the mimicry? One has to think it provides some protection from vertebrate predators. Also, these are among the largest of the robber flies, most of which are not mimics. That large size seems to slow them down, as they don’t fly nearly as fast as their smaller relatives. Perhaps the bumblebee coloration and speed leads prey to ignore them until it’s too late.

Advertisements

1 Comment

  1. Emerson Hampton said,

    June 3, 2013 at 2:15 pm

    Members of this genus in Florida are large, robust flies. The wings are smoky brown and the body has dense patches of black and yellow or white hairs. Bee killers resemble bumblebees and carpenter bees in shape and coloration. They generally mimic all of the five bumblebee species occurring in Florida (Stange 1992). They make a beelike hum or buzz when flying (Linsley 1960).


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: