---

The usual specimens we get are the Hornet Robber Flies, Asilus crabroniformis, so this one came as a surprise. Seen at the beginning of August 2013.

Location: http://www.glaucu...l2013.html

---

Could it just be a freshly emerged Asilus? Do you have more angles and can you give us an idea of their size, relative to the usual Asilus?

---

Thanks for you suggestion. I had it automatically down as Asilus until I saw the picture. And even then I was not sure until somebody else came up with the query from their own observations. Asilus is regularly seen at both sites as this one. But definitely smaller by 20% this one.

It is the only photograph. Instant reactions of point and shoot as it only settled on a chalky path for a second. Lucky to get it in the frame at all.

---

One of the normal Asilus. They are great predators on butterflies. From local observations second aerial predator to the Southern Hawker. Hundreds of prey items in an acre at the moment.

I think this one shows the relative sizes.

---

Addenda: behaviour and location was identical to Asilus. So were dates. But dates are still behind this year. Not three weeks like before the warm spell, but about a week behind for the butterflies.

---

Couldn't it be Machimus rusticus?

---

Thanks for the suggestion. Cross reference: http://72.44.83.9...pid=189406

http://www.insect...mp;t=90850

---

I think it is M rusticus but i should see a lateral image.

---

https://www.facebook.com/photo.php?fbid=10201970770899524&set=gm.325800567555559&type=1&theater

Same location, same year, possibly the same species: https://www.facebook.com/photo.php?fbid=10201970770899524&set=gm.325800567555559&type=1&theater

---

---

The above picture (by Su Reed) was found in the same location several times, but this is the first photograph. I have only seen one.

---

This last pictures is a female Tolmerus (Machimus) atricapillus (could also be T. micans but that species has never been recorded in the UK). In the Netherlands Tolmerus atricapillus is called the "Common robberfly", together with Dysmachus trigonus by far the most widespread asilid. In NL it is rarer on chalk grasslands in the south. Very numerous on sandy soils. Machimus rusticus, on the other hand is only found on chalk grasslands in NL.

I am pretty sure this is M rusticus but based on looks, location and shape of genitalia. In the UK there is a look alike, M arthriticus. This species has usually more red on tibia, more slender male genitalia and prefers a sandy soil. To be sure the underside of the front femora should be visible, if there is only hair it is rusticus, if there is a row of bristles too then M arthriticus.

---

Thanks for the last reply. I have independently IDed the last picture as Machimus atricapillus Unsure now after a break. Linked in picture to this discussion. The first one was assumed to be the same species. It might not be though?

---

No, last picture is not the same species as the one in the first picture. Asilidae might be a difficult lot but.... Last picture is Tolmerus (Machimus) atricapillus 99.9% : ) First picture is probably M. rusticus by default again.