What is this fly with legs like a flea?

[rjlittlefield]

I have a book on order: https://www.amazon.com/gp/product/041256520X "Scuttle Flies: The Phoridae" by H. Disney, 1994. Current list price $299 but out of stock. Amazon found me a copy in the UK for less than $30 including shipping. (No, they aren't offering any more for that price.) I'll report back after the book arrives and I've had a chance to do some reading.

Update: The book arrived some time ago, and I've read bits and pieces of it.

The book is dense and highly technical, 467 pages in total, with 178 pages just in Chapter 8 "Identification". Most of that goes only to genus level.

Speaking of "genus level", the book's index lists 236 species of Megaselia. But that was in 1994. At this moment in 2021, the Phorid Catalog at https://www.phorid.net/pcat/ lists 1690 species of Megaselia worldwide, with about 235 of those labeled as USA, N America, or cosmopolitan.

I was interested to see that the home page at https://phorid.net includes a navigation link, "How to recognize Megaselia scalaris, the most commonly seen phorid". The link goes to a file named "scalaris.php", which unfortunately is not present on the website or captured in the Internet Archive's Wayback Machine. I've sent some email to try tracking that down.

--Rik

[quenoteam]

Megaselia scalaris
Can it be the same specimen as this little fly that I captured in my house in Malaga (Spain) that was on an open melon?
It was extremely small, as you can see on my hand

Phoridae by Javier Rupérez, en Flickr

Phoridae by Javier Ruperez, en Flickr

[rjlittlefield]

Megaselia scalaris
Can it be the same specimen as this little fly that I captured in my house in Malaga (Spain) that was on an open melon?
It was extremely small, as you can see on my hand

I would bet pretty heavily that yours and mine are not the same species.

For starters, yours has an obvious "collar" of prominent setae around the rear margin of the eye, where with mine those setae are absent or at least much reduced. I point out this feature because the same area is seen clearly in both pictures, and the feature is clearly different.

I have no doubt that these two files are closely related, quite possibly in the same genus.

But there are a lot of species of these flies, and if you read what I wrote in the rest of the thread, you'll see that even the specialists often get it wrong, despite working with multiple specimens and knowing (in principle!) what to look for. The story of Megaselia globipyga, recounted HERE, in which the type series was later found to contain at least three actual species -- one for the holotype and two more among the paratypes -- should give pause to any non-specialist who is inclined to stick a specific name on one of these flies. Such naming is at best an act of faith, not solid science.

--Rik

[quenoteam]

Yeah well I think I'll leave it on "Phoridae"
Within the phorids the genus Megaselia, is one giant group, and the 1400 species currently described is just a drop in the bucket.
Surely it is Megaselia too, but I will not dare to assure this
I think there are thousands of very similar flies

Regards

[DavyC]

What is this fly with legs like a flea?

A quote from 'Rik and the Beanstalk'

'Flea Fly Foe Flung' lol.

When flies turn rogue, really annoying, in your face. Like they have a death wish,
I have heard them called 'D*mn Flies'.
This has got to be one of those D*mn Flies!