Of most malacologists no archival data is preserved, and especially complete correspondence archives are rare. So if one tries to reconstruct the contact network one may use a few sources; e.g., in publications often several names turn up as suppliers of material (either as field or as cabinet collectors), in the collection (if preserved) labels may point to collectors or colleagues with whom material was exchanged, and (in some rare cases) correspondence may reveal some of the contacts.
In the case of Henri Drouët (1829–1900) all three sources could be used and revealed a quite extensive contact network of more than 100 persons. The following figure gives a picture of his network, distinguished according to the following roles: malacological authors (MA), authors from other disciplines (AO), field collectors (FC), and other contacts (OT). The persons in the first three categories all received one or more eponyms.
This picture also makes clear that eponyms may be used as a proxy for contacts of an author.