How did Vladimir Nabokov fund his butterfly-hunting expeditions?

Vladimir Nabokov funded his butterfly-hunting expeditions primarily through the money he earned from the German translations of his early novels.12

During his years of European emigration, Nabokov lived in a state of continual semipenury, as his books did not produce significant income until the success of his best seller Lolita. To support himself and his family during this period, he also worked by giving lessons in tennis, Russian, and English, and by taking occasional walk-on parts in films. His lifelong passion for entomology eventually led him to publish 18 scientific papers on the subject.12