Andrena male big head huge jaws!

[JRsbugs]

Thanks Matt, I have tried several times to download the "Test Keys for UK Andrena species" from BWARS" without success, Adobe can't open it. I can download all the other pdf files there. Any suggestions on how I can get this?

From what you have told me appears to rule out A. nitidiuscula, but there is still the matter of the head shape (as viewed from above) of A. denticulata on the Dutch keys which also appears to rule that out.

I'm not totally convinced that bees will only feed on one family of flowers, they may have preferences but there must be exceptions to the rule as I know there are in other bee species where for example Colletes hederae forages on other flowers when Ivy is not in flower.

The Dutch text does state "the species almost exclusively visited Apiaceae, especially Daucus and Levisticum" I have Levisticum too, aka Lovage.

Also, I wouldn't view the Dutch use of the word "remarkably" in the same way you view it. I have a Belgian friend who also speaks Dutch and have seen how the continental translation or general use and meaning of words differs to ours. This particular word "remarkably" I would see more as "interestingly".

[JRsbugs]

I can finally show that this is not Andrena denticulata. The German site wildbienen has a photo of a male which clearly shows the head "quadrately produced behind the eyes in the male, posterior margin deeply emarginate" as in Saunders keys. This is one character which in no way can be misinterpreted, no matter whether or not it is taken from another key.

You will need to click on the left link 'sand bees' to find Andrena..

Google Translate

So, this leaves it with not being either of these two species assuming that A. nitidiuscula never has a tooth.

I managed to find the test keys for Andrena on google but still can't download the document, I can get the 'quick view' which doesn't have illustrations.

[Matt Smith]

Now I'm lost with your reasoning. Saunders description says:

A. denticulata, Kirhy[Listerdla, Kirb.).—vertex shining, quadrately
produced behind the eyes in the male, it's posterior margin deeply emarginate,

The bee in your photo certainly fits these characters. The photo I posted from the Duch site is the same. TBH, I would not like to comment on the photo on the German site as it its too small and dark to see much detail.

Why suddenly is it not A.denticulata based on a single poor photo?

[JRsbugs]

Originally Posted by Matt Smith

Why suddenly is it not A.denticulata based on a single poor photo?

The photo on the German site does show a 'deeply emarginate' hind margin behind the eyes, if you use a magnifier it's more obvious. You can see there is a groove with a ridged margin along behind the eyes, my bee doesn't have that but is smooth and rounded.

I have looked at the keys for males which I found without figures, it takes me directly to Andrena varians. I thought I had an Andrena varians female last year but I couldn't quite see the tail end enough.

There is one photo which shows the antennae segments 3-4-5 with 3 equalling 5 and 4 more or less square. The other option is for them being equal, that is clearly not so and the previous couplet alternative doesn't fit with 3=4 and 5 slightly longer.

This is in the section for Andrena males with hind end of head deeply excavated, hind angle strongly pinched, in side view angular box-ended and non-striate. Jaws usually with basal tooth or at least angulate. Jaws extra long, as crossed swords.

1. Body with mainly pale brown or whitish hairs.
2. Propodeum sides with pale hairs.
3. Sternite 2 with entirely dark ground colour.
4. Antennae beneath with segment 3=5 but 4 almost square. (I measured with marking them on paper).

Look at the antenna on the far side of this pic, enlarged again you can see it.. and it doesn't fit anything else along the way.

[JRsbugs]

I've marked out the segments..

[eucera]

I have been looking at collected specimens of A. denticulata and A. nitidiuscula under a microscope today. This bee just doesn't look like any A. nitidiuscula that I have ever seen. A. nitidiuscula really is a bee associated with coastal undercliffs and calcareous grasslands in the south of England (all south of the Thames). It would be way, way out of range for this to occur in your area, whereas A. denticulata is commoner, and much more widespread.

I appreciate that things can turn up well away from the home range (I have, after all, been involved with the Callicera rufa in Bedfordshire story personally). In that case though, we had a specimen. I have heard not a single instance of A. nitidiuscula appearing anywhere out of the ordinary recently, and the very restricted populations seem completely stable

[Matt Smith]

Originally Posted by JRsbugs

I have looked at the keys for males which I found without figures, it takes me directly to Andrena varians. I thought I had an Andrena varians female last year but I couldn't quite see the tail end enough.

There is one photo which shows the antennae segments 3-4-5 with 3 equalling 5 and 4 more or less square. The other option is for them being equal, that is clearly not so and the previous couplet alternative doesn't fit with 3=4 and 5 slightly longer.

This is in the section for Andrena males with hind end of head deeply excavated, hind angle strongly pinched, in side view angular box-ended and non-striate. Jaws usually with basal tooth or at least angulate. Jaws extra long, as crossed swords.

1. Body with mainly pale brown or whitish hairs.
2. Propodeum sides with pale hairs.
3. Sternite 2 with entirely dark ground colour.
4. Antennae beneath with segment 3=5 but 4 almost square. (I measured with marking them on paper).

Look at the antenna on the far side of this pic, enlarged again you can see it.. and it doesn't fit anything else along the way.

Andrena varians is one of a number of species where the sides of the head are produced backwards so that in profile the sides meet at a right angle. The best example I could find to illustrate this is Andrena synadelpha taken from the Andrena test key, this species is used as the exemplar to illustrate the "sides of the head" character.



Andrena varians would have a similar head shape but does not have the tooth at the base of the gena that A.synadelpha does.

The bee in your picture does not appear to have a head like this, but is much more rounded and not right angled as in Andrena denticulata below.



So, we have a bee with a rounded edge to the sides of the head AND a tooth at the base of the gena, neither of which characters are found in A.varians.

When measuring the length of antennal segments, you must be looking directly at them from the underneath in order to get the correct measurements to compare the relative lengths of segments. I have looked at all the photos and can't find one where we could get the correct view of the anennae for measuring.

[JRsbugs]

Is there any way I can get a download of the document with diagrams Matt?

Both diagrams are not quite matching mine, none of the shots are exactly side on so I have tried to mark out where the visible sharp edge of the head is with red dots, I'm not good at drawing freehand with pencil! It looks to be somewhere in between the two.



I have also marked out where the 'deeply emarginate' hind margin behind the eyes shows on the photo of male A. denticulata on the German site, mine doesn't have that. The definition of emarginate as having a shallow notch, thus producing a 'marginate' edge or lip on the hind margin. This is as I see it as it looks to be on the German site. I can see how it could be interpreted differently depending on which way you look at it, these two definitions show different views on it..

emarginate - definition of emarginate by the Free Online Dictionary, Thesaurus and Encyclopedia.

emarginate - Wiktionary



The photo from the German site which I have lightened, the hind margin behind the eyes is sharp cornered with a 'marginate' hind lip. It's small but can be seen better using a magnifier.



You state:

Andrena varians would have a similar head shape but does not have the tooth at the base of the gena that A.synadelpha does.

So, does A. varians have any sort of tooth? A. synadelpha doesn't look to have much of a tooth in the drawing, neither does A. denticulata. Both look to have a forward projecting bump rather than a tooth, where mine has a sharp tooth going in a backwards direction with a slight lump on the mandible.

Although I have marked out the antennal sections from above, the sections are visible on the underside albeit not totally beneath, I would have thought that was close. If you look at the other options I don't think any of them would come close.

[Matt Smith]

Originally Posted by JRsbugs

I have also marked out where the 'deeply emarginate' hind margin behind the eyes shows on the photo of male A. denticulata on the German site, mine doesn't have that. The definition of emarginate as having a shallow notch, thus producing a 'marginate' edge or lip on the hind margin. This is as I see it as it looks to be on the German site. I can see how it could be interpreted differently depending on which way you look at it, these two definitions show different views on it..

emarginate - definition of emarginate by the Free Online Dictionary, Thesaurus and Encyclopedia.

emarginate - Wiktionary

You have come across one of the commonest problems you bump into when using a variety of keys, that of the use of a specific term in a specific way. The same word may actually mean somewhat different things when applied to different areas of biology, keys for different groups tend to develop their own conventions of useage.

With Hymenoptera, "emarginate" is used along the lines of your first definition, that of a notch or "indentation" in an otherwise "straight" surface. The modifier "deeply" means just that - a "big dent".

When considering the "hind margin of the head", you have to consider it in its' entireity, not just the top edge of the head and work on the principle that the most rearwards part of the head you can see when looking directly down on the head constitute the limits of the hind margin of the head. The degree of "emargination" (ie the size of the dent) is considered based on this.

I could not find an image of A.denticulata, but here is an illustration of the head of A.floricola to illustrate my point:



I have marked up the picture to show the limits of the rear margin of the head (horizontal line) and the depth of the emargination that needs to be considered (vertical line). I would say that this had a "deeply emarginate" hind margin to the head, as does the bee in your photos.

So, does A. varians have any sort of tooth

No - "does not" means "does not" - there is no tooth of any sort.

Although I have marked out the antennal sections from above, the sections are visible on the underside albeit not totally beneath, I would have thought that was close.

The problem here is that antennal segments are frequently longer on the upper surface than the lower surface - I have confused myself more than once looking at specimens because I have not looked at the antennae in its correct orientation as asked for in the keys. There is a difference, some species have antennal segments where the upper sides are 50% or more longer then the lower sides, so you do need to see them directly from the ventral side to make the measurements.

[JRsbugs]

Originally Posted by Matt Smith

You have come across one of the commonest problems you bump into when using a variety of keys, that of the use of a specific term in a specific way. The same word may actually mean somewhat different things when applied to different areas of biology, keys for different groups tend to develop their own conventions of useage.

With Hymenoptera, "emarginate" is used along the lines of your first definition, that of a notch or "indentation" in an otherwise "straight" surface. The modifier "deeply" means just that - a "big dent".

When considering the "hind margin of the head", you have to consider it in its' entireity, not just the top edge of the head and work on the principle that the most rearwards part of the head you can see when looking directly down on the head constitute the limits of the hind margin of the head. The degree of "emargination" (ie the size of the dent) is considered based on this.

I could not find an image of A.denticulata, but here is an illustration of the head of A.floricola to illustrate my point:



I have marked up the picture to show the limits of the rear margin of the head (horizontal line) and the depth of the emargination that needs to be considered (vertical line). I would say that this had a "deeply emarginate" hind margin to the head, as does the bee in your photos.



No - "does not" means "does not" - there is no tooth of any sort.



The problem here is that antennal segments are frequently longer on the upper surface than the lower surface - I have confused myself more than once looking at specimens because I have not looked at the antennae in its correct orientation as asked for in the keys. There is a difference, some species have antennal segments where the upper sides are 50% or more longer then the lower sides, so you do need to see them directly from the ventral side to make the measurements.

I hope I'm not giving you too much trouble over this Matt! If the back of the head shape had matched A. denticulata I would have been content to call it that, but it still doesn't fit in my eyes. I have tried to imagine that it might look more like the drawing, and the male shape on the German site if it was from directly above but somehow I still can't make it fit.

I would trust that the photo of the male A. denticulata on the German site is correct more than any others, the site has some basic keys as well and I doubt they would have put a photo at all if in doubt. I have blown that photo up by 400% and arrowed where the margin as described and shown in the Dutch keys is, it fits! There is also the question of how Saunders would have viewed 'emarginate' as opposed to the current view. I somehow think he would have viewed it differently but that is supposition, however I see no reason why anyone would use it differently for bees than for wasps at that time. Maybe this distinction has been muddied since then? There's no real proof other than what I see, and the Dutch keys will be old too as the language is from pre 1950, slightly different to current Dutch language.

I have been finding as much information as possible, A. varians obviously is not correct either as you mentioned it has no tooth, I found a reference to that in the Alan Stubbs 2010 test keys. These keys are a little disjointed though, it appears the 2010 updates are at the top with an older version below. I could only find a reference to A. denticulata in the older version, where there is one feature which doesn't fit (apart from the head as I see it!). That is the hind metatarsus lanceolate (tapering at either end). The metatarsus (or basitarsus which is the first long segment of the tarsus) on my bee has parallel sides, as shown in this photo and it is nowhere near tapering at the ends which I think would show.. there's a drawing of bumblebee legs which shows where the matatarsus is for those who don't know..

Bumblebee Legs



Re the antennae, as mentioned I did measure the bottom part and the photo I did this on shows the antennae from more a side view so the joints as seen at the bottom should not be far off the underneath. These segments don't quite fit the fig. 71 for A. varians either so that's two things against it, but the side view I have might prove to be useful for determining what it is. The whole of the antenna is in focus to the end so I doubt any variation is possible due to angle, there is only a little blurring from the flower being in the way.

I blew up my photo to 200% and made a snip of it too.. so here's the German A. denticulata male and my bee blown up.. and the part which says the metatarsus on A. denticulata is lanceolate..



Interstingly it does appear that A. varians has a small blunt tooth, which mine also has but there is that sharp one further back which doesn't match anything I've found so far. Look at this A. varians male on flickr.. terraincognita96 I have found seems to know a lot about bees.

Mining Bee (Andrena cf varians) #1 | Flickr - Photo Sharing!

The plus side to all this is I am learning a lot about Andrena species (hopefully helping others too!), and I think I have found the ID of a male I had last year which looks to be A. helvola male, the tooth and description matches one I found on flickr. I'll try to post that one later on another thread, this is all good educational stuff!

I was confused by the Alan Stubbs key in the section for determing which group for the males, I got to where it said to go to #6 but that's where it ended! I now wonder if this #6 is in the older section at the bottom. Maybe I shouldn't have been using the group with big box head, long crossed jaws etc. but my bee looks to fit in that group. More researching to be done yet.