B.W. Westermann, a Danish merchant, was a pupil of Johann C. Fabricius, one of the chief founders of scientific entomology. In 1816 he travelled to the East Indies and collected insects in Bengal (eastern India) and Java, Indonesia. On his way back to Europe he stayed at the Cape of Good Hope for some time during the summer of 1816/1817 and went on several excursions with the apothecary Carl H. Bergius* to collect insects. The results did not meet Westermann's expectations. He had been at the Cape before during the rainy season - perhaps on the outward leg of his journey - and expected better collecting in the summer.
Years after his return to Europe Westermann published a paper entitled "Ueber die Lebensweise der Insecten in Ostindien und am Cap" (On the habits of insects in the East Indies and at the Cape) in the Magazine der Entomologie (1833, Vol. 1, pp. 103-115). He does not appear to have published anything else. The moth genus Westermannia was named after him.