Sphecidae: Male Crossocerus pygidium

[Jason Green]

Evening all,

Just a quick question. I have a male Crossocerus, and Richards (1980) is asking if it has a pygidial area. My specimen has a notably-punctured T7, and I'm just wondering how I can tell if it has a pygidial area or not. All of T7 seems to be 'as one' with no additional lines or structures (as examined under x50). Still, I've never been asked this of a male before and thought I'd just ask around.

Thanks!

Take care,

Jason

[Matt Smith]

Originally Posted by Jason Green

Evening all,

Just a quick question. I have a male Crossocerus, and Richards (1980) is asking if it has a pygidial area. My specimen has a notably-punctured T7, and I'm just wondering how I can tell if it has a pygidial area or not. All of T7 seems to be 'as one' with no additional lines or structures (as examined under x50). Still, I've never been asked this of a male before and thought I'd just ask around.

TBH, I have never noticed this couplet before, mainly because I use Richards as a "last resort" when keying Sphecids, so I very rarely take an insect through the whole key.

Looking at the key, Richards leads off the male key to Corssocerus with this "pygidial character". I take his useage of the word to mean the whole center of the surface of T7 is considered the "pygidial area". Reading the choices, you either have to go for "pygidial surface flat" or "pygidial suface excavated and gutter shaped", so I would suggest that unless you can see a definate "gutter" shap go with "flat".

For most solitaries, I tend to use the key in "Solitary Wasps" by Yeo and Corbet as a first choice, which only uses a pygidial character once, right at the end of the key. This is backed up by Lomholdt "Fauna Ent Scand: Sphecidae", in particular for the illustrations, with Richards coming a distant 3rd.

Still, it is handy to have all three as each takes a different approach and it is useful to sometimes have 2 different ways of splitting a species pair or species group. However, it is my copy(ies) of Yeo and Corbet that have most of the margin notes of characters and pointers from the other keys.

[Jason Green]

Thanks Matt, I hadn't considered the male's pygidial area could be described as such using the same criteria as the female. Well, the punctation is present along the central line with no apparent gutter around the tip - so seems to be 'flat'. Onto couplet 36 then. The mid-femur is obviously widened more at it's base and the pronotal collar is just as thick when it terminates at the sides as it is halfway along - resembling fig. 127b, p101. It looks good then for elongatulus, except I'd describe the clypeus as tri-lobed rather than weakly-quadridentate.

These black Crossocerus don't get much easier, do they!