Robber fly with prey

tough, tough....
my comparisons (so far) Philonicus rufipennis, Machimus antimachus but... not sure if either occur in the PNW, Neomochtherus willistoni

comments (10)

Christine Young

Lion

Really fantastic photo. I have no idea on the ID, but suggest looking at Neomochtherus sp. as well. Posted 4 years ago

Ferdy Christant

Lion

I probably can't help much, but still want to pass on an interesting key that I learned today. It's quite subtle:
https://inaturalist-open-data.s3.amazonaws.com/photos/90353414/original.jpg?1597619105

If you look closely, you can see how only the thigh of the front leg lacks the thick black bristle hairs. All other legs and leg sections do have them. This is not true for all species, so can be something to narrow down the list.

Another are the hairs on the thorax, in particular where they begin. In some species, hairs already begin near the "neck", whilst in a species like yours the hairs only start halfway the thorax.

There's also beard length and color, the abdomen shape and curve, and of course genitalia.

So uhm yeah, good luck :) Posted 4 years ago
1. morpheme
  
  Lion
  
  OK - you've got me super intrigued... that robber fly looks more like my fly robber than any I've found so far... but the link leads to a photo and I can't figure out how to get to the key from there. Cutting off the link after the .com just gave me a whole ton of raw data.. Posted 4 years ago
2. 1. Ferdy Christant
    
    Lion
    
    Sorry, my bad. The photo is of a species on your own candidate list: Machimus antimachus. I got triggered because earlier today I identified another in the same genus:
    
    Posted 4 years ago, modified 4 years ago
  2. 1. morpheme
      
      Lion
      
      Doh - you got me there.. as much as I'd love to be able to, there's no other languages that I can read fluently. I have found some keys, but I find they are a bit advanced for a lay person (and often include characteristics that would likely mean the specimen would have to be dead to examine them...) Some are in English and some in German.
      http://www.geller-grimm.de/key.htm Most of what is on BugGuide appears to be based on this guy's research. Posted 4 years ago, modified 4 years ago
    2. 1. Ferdy Christant
        
        Lion
        
        You know it's good when there's a CD-ROM!
        
        Have a look at this one:
        http://waarneming.nl/download/fotogidsAsilidae.pdf
        
        I know, also in dutch. But it may have some general use for future cases:
        - Clear photos to find the correct subfamily
        - Page 13-16 shows keys in a very visual way, then you at least know what to look for
        
        Applying the keys is hard and species in your area are not in the guide, but I keep coming back to this one as a starting point. Posted 4 years ago
3. Christine Young
  
  Lion
  
  Wait, I'm confused...I thought that Machimus sp. have the macrosetae (long bristles) on the back of their foreleg femur? That's why I suggested Neomochtherus sp. (this genus lacks the macrosetae on the posterior of the foreleg femur). It looks like morpheme's robberfly lacks these bristles on this femur...or, maybe they are camouflaged by the prey? Posted 4 years ago, modified 4 years ago
4. 1. Christine Young
    
    Lion
    
    Ohh....Ferdy - you're talking about the black bristles, right? I was referring to the pale ones. Posted 4 years ago
  2. 1. morpheme
      
      Lion
      
      hmmmm - I have other photos that I've also been using for ID purposes. I can say that I think the front femur does have some pale setae, but they are pretty sparse and short, especially compared to the other legs and indeed no dark ones. The legs are all red and I believe each femur has a black bar on it's face. It has pulvilli (footpads - I had to look that up to even see what it was...) and 2 segmented antenna. The facial hair is neither very dense or very sparse.. middling. I wasn't able to get a front to view - it was up in a tree! I was lucky it tolerated my bending the branch down as far as I did.
      
      This photo https://bugguide.net/node/view/144668/bgimage and the distribution, confirmed to be in this area, makes me think you are right about Neomochtherus
      
      update - BugGuide has placed it in Neomochtherus. There's only 7 of 13 (10 western) species listed there at the moment. Posted 4 years ago, modified 4 years ago
    2. 1. Christine Young
        
        Lion
        
        That's great that you got confirmation, and with so few documented, it is a valuable observation! Posted 4 years ago, modified 4 years ago

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By morpheme

Uploaded Sep 3, 2021. Captured Sep 2, 2021 15:39 in Waughop Lake Loop, Lakewood, WA 98498, USA.

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Captured in the summer. More summer photos.