So whatever happened to the insertion arias Mozart wrote for Anfossi's opera?

These are the arias K418, K419 and K420, first presented at Mozart's Akademie of March 23, 1783 at the Burgtheater, in the presence of the Emperor. This Akademie, and a number of others taking place between November 1782 and March 1783, also saw performances of the piano concertos K413-415 written for these occasions . Beyond that the arias simply joined the Mozart canon of concert arias like all the others, and from then on get performed, as & when, that way to this day.

The first two arias, K418 and K419, were written for and presented by Aloysia Lange, aka Mozart's sister-in-law, née Aloysia Weber. These, together with the tenor aria K420 for Adamberger, were then subsequently used in a production of Pasquale Anfossi's "Il curioso indiscreto" in its Vienna production of that same year, 1783. A further aria for the same composer's "Le Gelosie Fortunate" follows for its Vienna production of 1788.

K418 "Vorrei spiegarvi, O Dio!"

http://www.youtube.com/watch?v=0x5WmiBVCP8

K419 "No, no che non sei capace"

http://www.youtube.com/watch?v=XZ3hdDJPKnk

K420 "Per pieta, non ricercate"

http://www.youtube.com/watch?v=h42KvHP0Hzw

I'm afraid I can't recall the manuscript status for these particular arias, just 'on the hoof', but if you nip across to the NMA-on-line, and seek out the volume of concert arias concerned, you should find it detailed in the specific commentary to each, if known. I'm afraid I just don't have the time to do that for you right now... :-)

Though one or two of Anfossi's operas have been recorded more recently, a quick scout of the Amazon database doesn't reveal hide or hair of 'Il curioso indiscreto' so that may prove a pleasure for you still to come at some possible point in the future... ;-)

All the best,

They got used in a pet food commercial.