Enlisting in the service of the Congo Free State, he reached Banana in 1889, beginning his career there as deputy to Van Dorpe, Commissioner to the Cataractes District.

While he was ordered to meet certain quotas of rubber harvesting, Lemaire made little effort to do so, citing the lack of proper infrastructure and workers.

He had refused to meet the quotas, writing in a letter he had sent to the government “We will have to be cutting off hands, noses, and ears if we intend to collect rubber in the Équateur district (where no preparations had been made).

In June of 1893, Lemaire was replaced in his role as commissioner by Leon Fiévez, in part due to his failure to meet rubber quotas.

Other members of the expedition included caravan leader Justin Maffei, Belgian painter Léon Dardenne [fr], and geologists Jean De Windt and William Caisley.