Reader Mark Sturtevant kindly sent me a batch of photos the other day, allowing him to jump the queue (such as it it) since I’m traveling. His photos deal with a subject dear to my heart: mimicry.
Many insects will mimic a venomous or otherwise unpleasant animal model, and thereby gain a degree of protection from predators that have learned to avoid those models. Since predators can be sharp eyed (as is the case of birds), mimics are sometimes seen to closely resemble their models in all sorts of little details. However, not all mimics seem to closely resemble a particular model (at least to our eyes). But it seems reasonable that even a slight resemblance to something nasty can provide a degree of protection, and it would be from this beginning that a line of mimics might improve the fidelity of their deception if so needed and if the favorable mutations arise.
Here are some examples of insect mimicry that I found over last summer, along with some of their possible models.
First we have a model which is one of the local yellow jacket species. After much deliberating I have come to favor its identity to be a queen downy yellow jacket (Vespula flavopilosa), , owing to its large size and abdominal and facial markings:
Next is a very large syrphid fly (Temnostoma alternans), which seems a quite passable yellow jacket mimic.
Another model wasp. This is a square-headed wasp (looks like Ectemnius continuus), and as you can see it is carrying a syrphid fly that it has paralyzed. It will sequester it and lay an egg on it. Of course the story that will then play out is that the wasp larva will eat its helpless host alive. I found this wasp while sitting one day on a forest floor, photographing a halictid bee that was nesting in a rotting log. Then along came this wasp with its prize. She was so intent on completing her task that she crawled onto my leg and then used that altitude to take off toward her hiding place. But back to our story.
Next is a possible mimic of that square-headed wasp. It is yet another syrphid fly (Temnostomasp.). Ironically, I had photographed this same fly on the same day and in the same patch of forest, but did not make the connection until recently.
In the previous two cases, we saw that syrphid flies can be pretty close mimics to their hymenopteran models. Syrphid flies face one challenge which is that their models have long antennae, but the syrphids belong to one of many fly families with very short antennae. So how might flies with short antennae pretend to have long antennae? I am sure the WEITers will see the rather clever answer in the above pictures.
Next are some other mimics without their models. This strange fly is a thick-headed fly (Physocephala furcillata), and as you can see it has no problem with short antennae. These flies are mimics of thread-waisted wasps (see here). This fly shows another cool detail that many flies use to make them look more waspy. Flies have but one pair of wings, but bees and wasps have two pairs. The front and back wings will overlap in these insects, and this can stack up the pigmentation of the wings. Further, certain wasps fold their forewings longitudinally (you can see an example in the above yellow jacket), and this also stacks up wing pigmentation. So flies that mimic wasps will often have a distinct area of pigment on their wings as well. This is clearly visible in the thick-headed fly, but both of the above syrphid flies have a zone of pigment on their wings as well. This did not come out well in the first syrphid because of the camera flash, but you can see it in the 2nd syrphid fly above. I really like how mimics cobble together these fake details from this or that to increase resemblance to their models.
Finally, we have a lovely longhorn beetle known as the locust borer (Megacyllene robiniae). Although this beetle is not what I would consider a convincing mimic, its color pattern is thought to be suggestive of a yellow jacket or something. Perhaps this resemblance is enough to help it be overlooked by predators since like the above flies it too is commonly found foraging on flowers where a high % of the insects are hymenopterans. Although this insect is a pest as its larvae damages locust trees, it is a lovely insect and I have quite a few pictures. The adults are commonly seen on goldenrod late in the summer, but this individual shows that perhaps they are attracted to yellow flowers in general. One of my goals is to get good pictures of these beetles from the side, as their underside is also quite colorful.
I’ve seen those wasp-mimicking syrphids — rarely, because I probably don’t notice that they aren’t wasps most of the time. Not only do they carry their front legs to look like antennae, they also constantly tap them on the surfaces in front of them, just like actual hymenopterans do with their antennae. I had supposed that they’re trying to fool large predators; never thought about parasites.
I love these too. I remember an old book I have somewhere on Mimicry, which I can’t put my finger on just now. It was old (1950s?) and small and had numerous examples. I was tempted to carry it around in my pocket to show everyone, but not everyone would be as chuffed.
I bet you’re talking about Wolfgang Wickler’s book on mimicry, which I used a lot for lecture illustrations.
That’s on my shelves as well.
Beautiful pictures! Small question: what is that yellow flower in the last picture? Looks like it could be a goldenrod.
It is not goldenrod. My best guess is a variety of daisy or small sunflower.
… or coreopsis, but it’s hard to tell from the bit shown.
Thanks for sharing your wonderful photos and observations!
Thanks for these! I’ve videoed a number of these and had no idea what they were – great images in info.
Splendid pictures, Mark! Special congrats for the Ectemius with her prey – even if she was very obliging, you were at the right place with your camera ready at the right moment. I’m especially fond of the thick-headed fly. If I remember well, these flies are not only mimicking hymenopterans, but also parasiting some of them, inserting their eggs in the abdomen of poor bumblebees eaten alive by the larva.
Thanks! It is not unusual for me to be taking a picture of something, and then along comes something else… then something else… I eventually realize that I had been sitting in one spot for over an hour, and my knees are killing me. Then comes the reluctance to move on. What if something important wanders in to this magic spot?
This picture of the thick headed fly is not as good as I wanted, but it was the best of several individuals that I had encountered. I will eventually nail it.
Possibly the ‘magic’ of the spot is the absence of noisy lumbering tetrpods, just this large lump that makes occasional ‘click’ noises? A geologist’s field lesson is to “look before you piss”. But as an entomologist, you probably look (again) 10 minutes later.
HA ha! Good advice! But it’s perhaps worth looking again once you have finished micturating as sometimes details show on wet rock that are hard to see when it’s dry!
Spitting on a rock surface (or just breathing, on a freshly-fractured surface) is an established technique for enhancing the contract between different parts of a structure. Works particularly well for fine structures and fossils in dark mudrocks.
The look-before-you-piss lesson is one normally learned with excellent quality fossil or mineral specimens that you’d have seen from a hundred paces away at midnight, if they hadn’t been in a fairly out-of-the-line-of-sight place (which is why you went there for a piss). Still (30 years later), *my* best hand-specimen of mica at about 3x5x1.5cm is one that taught me that lesson. (I have better specimens – A5 sheets from a WW2 radar factory site – but I consider them as cheating. Almost as much a cheat as buying specimens from a mineral shop.)
Yeah, the red-spotted admiral would be attracted to the salts you deposited.
They used to love the old patio slabs, wherever the d*ggies peed.
(Pic from internet, not mine..
http://www.naba.org/chapters/nabanj/butterflies/red_spotted_admiral.html )
Great post, nice shots, thanks.
Great photos and a great read. Thanks for pointing out how the syrphid flies use their front legs to mimic hymenopteran’s long antennae. That is splendid!
More great stuff from Mark! Great stories as well!
Syrphids & wasps seem to have a nice little co-evolutionary duel going on.