Readers’ wildlife photos

November 6, 2021 • 8:00 am

Do send in your photos, as the picture tank drains inexorably.

Today’s photos comprise a sequence of insect predation and parisitism taken by reader Mark Sturtevant. His notes, links, and IDs are indented.

The hobby of searching for and photographing insects can lead to discovering moments of drama that would otherwise go unnoticed. Here are pictures that document a moment of great injustice in an insect’s life.

During one outing in a place that I call the Magic Field, I noticed a small movement on the ground. It was a solitary wasp, and she was hard at work digging a burrow. No doubt she would later provision it with paralyzed prey for her larvae. This is Prionyx parkeri, one of the thread-waisted wasps. You can admire here the long spurs on her front legs, which were of great help as she diligently raked up and carried away sand from her burrow.

Burrowing wasps may have different enemies who would seek to take advantage of their industry, so they instinctively try to conceal their work. Here she is about to fly away with a load of sand from the burrow entrance. This is done to remove traces of freshly dug soil. 

From this angle you can see that she has unusually elongated mandibles. This tells us that the prey she seeks will be paralyzed caterpillars, and that she will use those jaws to carry her prey much like how tongs would be used to carry a hot dog. But what is that fly doing there??

There were several of these flies. I counted four or five of them, all attentively watching her every move. 

This is bad news! These are Tachinid flies, although I don’t know the species. Parasites. More specifically, they are kleptoparasites, meaning that they intend to lay eggs on her paralyzed prey. Her motherly labors are not finished and her young are not yet born, and yet they are doomed.

I watched in fascination. After she cleared out the entrance, she then left. I did not understand until now that her burrow was actually finished, and that she was simply unplugging it to stock the burrow with new prey that was hidden nearby. In about a minute I could see her making her way back with a paralyzed caterpillar. Every twig and tuft of grass was a barrier, and her tireless efforts seemed a Sisyphian task.

She set down her prize at the entrance, and disappeared inside for what I suppose were final preparations. I wish I had managed to take more pictures here, but I had to ration the battery charge on the flash 

Immediately, one of the flies made its move. It landed on the caterpillar and inserted an egg onto it. You can see it if you look closely. 

The flies immediately backed away when she emerged. She moved the caterpillar inside, and after a time re-emerged to then carefully conceal the entrance before leaving. The flies continued their watch. 

Solitary wasps of this sort will make a burrow, but branching from it will be several individual chambers, each with a prey item and one egg. The remaining flies likely have good reason to continue lurking around this burrow entrance because the wasp will likely return with new prey for them.

I do regret not recording this scene as a movie with the camera, as that would have ensured that more details were captured. But the microphone would have also recorded a rather continuous stream of profanities from a grown man, face down on the dirt, who was very upset at some of the drama that probably happens every day in the Magic Field.

Readers’ wildlife photos

October 28, 2021 • 8:00 am

The photo situation is DIRE. Send in your good photos. I am not crying wolf here.

Today, though, we have a photo sequence of a robber fly taken by Emilio d’Alise. Robber flies are in the dipteran family Asilidae, and are all predators, many of them vicious.  As Wikipedia notes, “they feed mainly or exclusively on other insects and, as a rule, they wait in ambush and catch their prey in flight.”

Emilio’s captions are indented, and you can enlarge his photos by clicking on them.

Robber Fly (from Monument, Colorado, July 2014)

One fine 2014 July day, while squatting next to one of the lawn ornaments and snapping away at a flowering carnation plant, I head a sudden and loud noise — like a miniature outboard motor — right next to my face.

I’m not afraid of insects, really I’m not. I have an Official Bug Transport Vehicle (a.k.a. yellow Solo cup) I use to relocate various insects from inside my house to the great outdoors. Spiders, centipedes, multilegged, multi-eyed, small, large, it makes no difference to me; I capture them, and release them outside.

But I’d never seen one of these, and the first thing I thought was “GHOUL!”

Before I go onto the rest of the photos, please look at the photo below carefully . . . that white thing that looks like the bug’s face? Not the bug’s face, but another bug; one it had just caught.

Now, as I was shooting this, I had not noticed the other bug. I thought it was all one bug. I didn’t even notice the other bug when the Ghoul did this (sorry for the blur, but this thing was fast!) . . .

. . . and moved to the other side of the copper stem of the ornament. And let me tell you again; these things are FAST!

That’s when I noticed the captured bug, mostly because it was still alive and moving. The Ghoul had repositioned it so it could feast on the juicy parts of the unfortunate victim.

OK, so it’s not a ghoul (appearances aside) . . . it’s a Robber Fly. You can find more information about Robber Flies — a.k.a. the Assassin Bug — at this LINK.

I was worried it might fly off, but I risked repositioning to get a better shot (I had switched to shooting for speed, so I have a shallow depth of field).

I need not have worried; this thing was content to sit there and suck on its poor victim, which at this time was still moving . . . Let me tell you, I was glad this thing already had a meal as that’s one gruesome way to go.

The write-up says that  the Robber Fly is a medium-to-large bug, up to 5 cm – that’s two inches, and I estimate this thing to have been all of that.

In a few of the photos you can clearly see the “short stout proboscis enclosing the sharp, sucking hypopharynx” (text from Wikipedia).

I risked getting closer, and in a blur and outboard-motor noise, it flew off. Did I mention these things are FAST? I mean, it makes sense since they are predators . . . but when I say fast, I mean it crossed my yard, the road, and was lost from sight in something like a second and a half, maybe two.

I had never seen (or heard) of a Robber Fly before that day, but once I was familiar with the sound of their wings, I saw more (but smaller) whenever I went weeding, when I cut the grass, and when I watered the plants. In all, four or five times during the next week or so, but without the opportunity to snap more photos . . . until I went out to get the mail one day, and there were two smaller (about an inch and a half) on the concrete drive.

I snapped a few quick photos with my phone but since they didn’t seem interested in moving, I went and got my DSLR.

This shot below shows the female of the pair.


How can you tell it’s a female? I seem to remember reading the males have a white tuft on their rear end (I can’t remember where I’ve read that or I’d link it). If I’m wrong, please correct in the comments.

And, guess what? I had missed the fact the female was enjoying a meal . . .

The photos were captured with the Nikon 105mm macro lens, and for these last shots I was on my stomach, on the ground . . . the neighbors probably just shook their heads and went back to tending to their dogs and kids.

These Assassins didn’t seem perturbed by me moving on the ground around them, and they were still there when I tired of taking photos and headed back in.

I’ve seen (and heard) Robber Flies since, but I’ve yet to have another chance to snap more photos.”

In which PCC(E) tells people how to get rid of fruit flies

April 7, 2021 • 2:00 pm

This is not the first time I’ve been asked “how to get rid of fruit flies,” but this time it’s by a reporter for Chicago Magazine in the article below.

The first thing I had to ask when they queried me, was “what kind of ‘fruit flies’ are you talking about?” For the true fruit flies, the tephritids that endanger California’s fruit industry (that’s why you get inspected at the state border), aren’t a problem to homeowners.

What the reporter was asking me about was what geneticists call “fruit flies” but are better known to entomologists as “vinegar flies”. These are in the sister family Drosophilidae, and are the familiar Drosophila used in the lab. When you see little yellow flies buzzing around your fruit bowl, they are drosophilids, most likely Drosophila melanogaster or D. simulans.

And Drosophila are harmless, except to winemakers, and only because they’re attracted to the smell of alcohol and fly into the wine vats to die a happy death. (Flies love the smell of alcohol, as it denotes their real love, rotting fruit, in which they lay eggs.) Winemakers use pyrethrins, a fairly harmless pesticide derived from chrysanthemums, to control them.

If you see Drosophila buzzing around your fruit bowl or a glass of beer, don’t kill them, just shoo them away. They shouldn’t be breeding in your house unless you have a bunch of rotting fruit that’s sitting around for 12 days or so—and who has that?

(When I lived in Davis, I was called by a bar in Sacramento that really did have a Drosophila problem. A quick investigation showed that there was a huge bin of leftover, rotting lemons and limes from the bartender behind the building, and that was the source of the flies. For solving that problem, I got free drinks!)

But a reporter from Chicago Magazine was interested in how to get rid of them, along with three other “problems”: hiccups, alley rats, and hangovers. Somehow I was picked to be the fruit fly expert, and here’s my answer (click on the screenshots below to see the others, each with a different expert:

Well, this is advice for those with dipteraphobia. If you see fruit flies, just gently shoo them outside!

BBC show: Matthew and others on Drosophila

March 3, 2021 • 12:30 pm

The BBC is doing five ca.-15-minute shows on insects, and today’s is on my favorite insect (or genus of insects): Drosophila. It was broadcast this morning, but is now on the BBC site for your delectation. It won’t be there forever, so listen soon. The subtitle, “Drosophila Melanogastronaut” is clever, a play on the famous species Drosophila melanogaster, but they shouldn’t have capitalized the second word.

Erica McAlister, curator of Diptera at London’s Natural History Museum, introduces a number of talking heads, one of which is our own Matthew Cobb. It’s a short listen, and since your host spent his life working on Drosophila, you might want to learn a little about the fly. Click on the screenshot to listen how this humble fly (properly called the “vinegar fly” rather than “fruit fly”), kick-started genetics in the early 20th century.


The Infinite Monkey Cage takes on flies

January 11, 2021 • 2:15 pm

After an audience member demanded that the BBC’s Infinite Monkey Cage took up the subject of Drosophila, the show devoted its half-hour slot not just to Drosophila, but to flies in general (dipterans). It features not only the hosts Robin Ince and Brian Cox, but our own Mathew Cobb, Erica McAlister (a curator at London’s Natural History Museum), and “fly sceptic” David Baddiel, a British comedian.

As Matthew said, “It was a lot of fun. Erica is a hoot.”  It is a good show, and you’ll learn a lot about flies, and there’s a lot of laughing. Don’t miss the part about a botfly in the head (sadly, not the one I head).


April 30, 2018 • 1:15 pm

by Matthew Cobb

UPDATE: Matthew sent this computer-generated image of the robberfly’s venom system:

In case you didn’t know, today is World Robberfly Day on Twitter, so entomologists are posting pictures of these fabulous, chunky and aggressive flies, the apex predator of the Diptera. Go over and check out the photos yourself – here are just a few.



The gathering of the flies

October 28, 2017 • 12:00 pm

by Matthew Cobb

Here’s a lovely tweet by Japanese macrophotographer @muakbno. Look at all those flies! What are they and what are they doing?

@muakbno posted these pics with some explanation:

Twitter translation: “Chloropidae and flock to the leaves of a dark Companion. Touching leaves and flying in one formation can be distorted so with bated breath, calm approach. No matter how many similar upward along.”

Google translation: “A fellow of the flying fly that gathers one after another on the leaves of Misaki of dusk. Touching the leaves, if one flies, the formation will be disturbed and quietly quiet as you kill yourself. Regardless of the number, they are arranged in almost the same upward direction.”

Any Japanese readers want to improve on the translations? These are Chloropidae, tiny flies that are quite common in Japan, where there are 3 subfamilies, 53 genera and 143 species. More here.

But what are they actually doing? Why are they all grouped together? How could we work it out?

Gorgeous monster robberflies

September 11, 2017 • 1:00 pm

by Matthew Cobb

These monsters were posted by Piotr Naskrecki – another reason why you should be on Tw*tter!

We’ve posted about robberflies (Asilidae) before here, with a reader’s photo here and a fabulous robberfly in amber here. Go read about them! Amazing beasts. (I note in passing that PCC(E) doesn’t have a ‘flies’ category here. For shame! So now we do.)