Thanks. Given this is Portland, Oregon it must be flavitarsis?

Does the curling of the antennae give clue about sex?

You might be right with the species, I never tried to key them out, but I can tell you that this is a male for sure, which you can see by the long and slightly curved antennae... compare this with the other pictures, and you will see what I mean...
Cheers
Martin

Thanks so much for confirming what I thought I was gathering from some cryptic comments on other posts re: the curled antennae.

Course I have another question about this. Is the curled antennae diagnostic of sex across wasp taxa or true only in this genus?

(If there is something to read that is relatively beginner-friendly (I can handle technical stuff being a decent botanist just don't know my invertebrates) on this I am happy to be referred.)

And I am not capable of id'ing down to species, just making a good guess (I guess it is good) on the species on the basis of geographic range.

Thanks again!

In general the "stinging wasps" like bees, yellow jackets, hornets, Spider wasps etc have 12 antennal segments in the female and 13 in the male. Often the male antenna is also longer and thinner and often modified. So if you see such a long antenna with such a modification, it is very likely a male. This is true for Eumenidae wasps too. Yellowjackets and bees just have slightly longer antennae in males, but with a bit of practice, this is something you can see. In Pompilidae, the females have slightly curled antenna (http://bugguide.net/node/view/276923), while the males have more straight one (http://bugguide.net/node/view/516941), but there are many exceptions, this is just a rule off thumb.. In this case you can make the identification according to the distribution... this species is the most northern

Double Thanks for all those details. I will archive them for my reference. Now if only there were a question here I could answer for someone. All the best!