I've wondered about CS Larsen too. I have a few specimens with the same type of label, which came from the Aronheim collection, although they are Neotropical specimens. It appears that Mr Larsen had a very good collection!
Thanks for your most interesting information - I'd hoped that someone may know more! Tomorrow I'll pull the two specimens that I have with Larsen labels and will illustrate them here. Perhaps, between them, we may determine more of the story.
It seems that Otto Bang-Haas continued a link with Delias of the Bismarck Islands, for he is the author of D. mayrhoferi, described from New Britain in 1939. That description was "lost" for many years, the species later being rediscovered and redescribed as D. shunichii by Morita in 1996. The latter name was considered valid until the rediscovery of the original specimens in 2004; a paper sorting this out and reestablishing the proper name was published in Germany in 2006. I've briefly reviewed it a moment ago, and I don't see any indication of capture date(s) for the type specimens. The paper includes much other interesting historical information, and is well worth a look. Bang-Haas also published the little-known taxon Papilio moerneri mayrhoferi in the same year, likewise from New Britain.
I also think the link with Otto Bang-Haas would be the good one, as he had good contacts with German collectors in the Bismarcks (Mayrhofer has explained by Danny).
About "Ng Mecklenburg", I read it as the locality capture : - Ng would mean "New Guinea", "Mecklenburg" may be a locality there, Bismarck islands were a German colony in the past. - No idea what "Kapsü" could mean. An abbreviation with "Sü" meaning "South"? - I also read "A. Krück Hambourg" but no idea what it means but if "Modt." is the time of purchase, this "A. Krück Hambourg" should be the name of the shop/fair or of the seller.
I was right about "Ng Mecklenburg", it is the capture locality. I have just discovered that the German name of "New Ireland" island, where Delias bagoe flies, is Neumecklenburg ("New Mecklenburg") : en.wikipedia.org/wiki/New_Ireland_(island)
1) Polygrapha suprema: from Passa Quatro, Minas Gerais, Brazil; I had assumed that capture date was 20 January 1926, but this is apparently the date of acquisition by Larsen, per Jan's information. Labels are also shown from W P Comstock from 1939; presumably this is one of the specimens used as reference when Comstock wrote "The Genus Anaea".
2) Memphis lorna: from San Andreas, Ecuador; acquisition date 10 December 1924. There is another determination label by Comstock, but only similar to the previous specimen's small label and not the larger version. I can't decipher the other information on the Larsen labels.
Excellent detective work, what this hobby is all about at the end of the day, not only the specimens but the research, historical specimens are merely specimens if they have no history, if the story is lost over time the specimens, however great or rare, loose a bit in my eyes.
Jansons of London got all of Meek's specimens that Rothschild did not need, including many new and rare Delias. There are letters from the Natural History firm Staudinger and Bang Haas to Janson, in their archives at the BMNH dated between 1897 and 1929. They bought many specimens from Janson including those collected by Meek. They are no letters to Janson from Schück & Echten, so they may have been smaller dealers or collectors who bought material from Bang Haas, who continued the Natural History business after Staudinger's death. Those letters to Janson after 1925, would be from Otto Bang-Haas who took over his fathers business. I think it is probable (possible) that your Delias itamputi collected by Meek were bought from Janson by Bang-Haas, and then sold on. Unfortunately some collectors/dealers changed older labels, and added their own.
When I was recurating some of the Castniidae in the Natural History Museum in London a couple of weeks ago I noticed that several of the Duboisvalia types have the same Larsen labels as your specimens. His specimens were obviously well shared around.
My German friend Jens Jakusch has helped me decipher the itamputi label and found new interesting information !
What I read as "Schück & Echten" was in fact " Dr. Lück & Gehlen". And Dr. R. Lück and B. Gehlen had an insect shop in Schlossstrasse 31 in Berlin Steglitz and had some deals with Dr Staudinger and Bang-Haas.
Then Jens also found this newspaper from "Entomologische Nachrichten" where Lück and Gehlen were advertising a new arrival from "Holländisch Neuguinea" (= Dutch New Guinea). Guess in what year it was published ? 1911 !!! So maybe CS Larsen had read that newspaper before going to their shop to buy the itamputi !
The ad is in the "vom Markte" paragraph below :
CS Larsen will soon have no secret anymore for us !
Now you have the correct name of the German dealer, I can tell you that Dr. Lücke & Gehlen had correspondence with Janson between 1910-1927,almost certainly to buy specimens from him. So it looks as Meek's Delias itamputi with other specimens would have been bought directly from Janson by Dr. Lücke & Gehlen. If you were able to read Dr. Lücke & Gehlen letters in the BMNH (I guess they were able to write to Janson in English) you might even come across a payment for Meek specimens, that might include your Delias itamputi.