E.L. Clark resided in Durban and was a Fellow of the Entomological Society of London. He collected insects from about 1905, built up a fine collection of Lepidoptera (butterflies and moths) will all specimens properly labelled, studied their life histories, and preserved the larvae. Some of his specimens were presented to the Transvaal Museum in Pretoria (now the Ditsong National Museum of Natural History), but the bulk of his collection was sold to A.J.T. Janse* in 1920, when Clark had to give up his hobby because of domestic circumstances.
Clark was a foundation member of the Natal Scientific Society and was elected a member of its first council in September 1910. He became a foundation member also of the South African Biological Society in 1916 and was still a member in 1920.