Sphecidae - Passaloecus issue

Jason Green · #1 (**permalink**) 07-06-2011, 09:24 AM

Morning all,

I have a bit of a male Passaloecus issue - help please! It has one vertical and two crenate furrows, bidentate black mandibles (one rounded, lower one sharp) which feature a quite noticeable yellow-brown marking on each nearish the base, simple antennae with no noticeable 'teeth' and plain yellow palps.

Any ideas? I'm thinking either Passaloecus gracillis, corniger or eremita using Richard's RES key. Maybe the New Naturalist's book on these updates the British list or expands on descriptions, which I don't as yet have.

I'm pretty inexperienced with these, so any help appreciated. Photos on request.

Take care,

Jason

Jason Green · #2 (**permalink**) 07-06-2011, 01:50 PM

Set specimen

Best-I-can-do image

Mandibular markings

If it only had one horizontal crenate furrow then it would fit well for something like Passaloecus singularis. It has two CFs though, so that points towards gracillis with the converging eye-margins. The marked mandible is confusing me though - that's a feature of eremita though it should be white.

So, I'm thinking either singularis with a mis-interpreted furrow, or gracillis with an unusual jaw marking. I took another specimen nearby that lacks the mandibular fasciation, but is almost identical in every other respect including mesopleural furrows - just darker chitin-wise.

I'd be grateful for a steer, here

Take care,

Jason

htcdude · #3 (**permalink**) 07-06-2011, 02:00 PM

This is probably a stupid question but does melanism/leucism occur in these species? Maybe it's something like that which could explain to colourations of the markings?

Nige

Jason Green · #4 (**permalink**) 07-06-2011, 02:45 PM

Not stupid! I have no idea, really.

oxycera · #5 (**permalink**) 07-06-2011, 05:47 PM

That's the right group.
If the projecting middle part of the clypeus is untoothed its gracilis.
If toothed, then corniger has a large horn between antennae base, in eremita small and hard to see.

Jason Green · #6 (**permalink**) 07-06-2011, 08:32 PM

Ah, perfect. I'll have a look later, then report back. That mandibular-fasciation has me quietly thinking of eremita... but not quite the right colour, so perhaps either of the more common two.

Jason Green · #7 (**permalink**) 08-06-2011, 08:47 PM

I had a look earlier on - though I think I should really get a pair of WF20X before determining it.

From what I saw the clypeus is flat ventrally, so must be gracilis. Funny, the marking.