Three times a butterfly was named after the first curator of the Mission Museum: first in 1925, then in 1928 and in 1929. But it was the second that would have pleased him most because that was (and is) showcased handsomely in the museum's butterfly cabinet.
The Berchmans butterfly is a so-called bird moth, named for its form which is like a (small) bird. These thrive mainly in south east Asia. Berchmans must also have been interested in this species before it was named, because in a photo from a mission exhibition in Rome in 1925, he appears to be standing next to a box containing ten of these specimens. Here he proudly poses in front of his butterfly collection, an item that was highly prized in Rome.
Berchmans was an inspired entomologist. His love probably blossomed during a four-year sojourn at the Espírito Santo mission post in Brazil from 1896 to 1900. He personally put together a butterfly exhibition in Steyl in 1933, about which a German publication lists the 'Ornithoptera lydius Berchmansi' (the butterfly's scientific name) as one of its highlights. Incidentally, it is actually a subspecies, a rare variant of the butterfly found on the Moluccan islands.
The name of Ornithoptera lydius berchmansi was given by P. J. van den Bergh LZN, who gave the following reason for it: "I have named this rare variety Berchmansii in honour of the Reverend Father Berchmans from Steil near Tegelen, who has so often been helpful to me with the collection.” At the time of naming, van den Bergh reports that he himself has two specimens of the butterfly in his collection and that one specimen is to be seen in Steyl.
Berchmans was active in that field, he corresponded a great deal with fellow entomologists. And that bore fruit. Several labels and specimens by van den Bergh can also be found in the Steyl collection, and they may well have ended up here through scientific exchange. However, in the aforementioned German publication Berchmans also mentions a donation of a comprehensive collection of butterflies from an esteemed collector, but unfortunately does not give a name here.