Since 1954 the classicist Herzer Palace has housed entomological collection as a separate department of the Varaždin City Museum, where a valuable and unique collection, assembled by the most eminent Varaždin natural scientist, a grammar school teacher and the founder and the first curator of this department, Franjo Košćec is kept.
At the end of the last century Košćec' collection was completely restored and since then permanently exhibited under the name The World of Insects. According to the specialists and audience that visit the exhibition it is one of the most beautiful of its kind in Europe. There are about 4500 exhibits which clearly show biology of bugs through several topics: In the forest, Near the forest and on the meadow, In the water and near the water, At night and underground. Various objects that can be seen here include entomological preparations, mounted vertebrates, preserved plant specimens, enlarged models of bugs, photographs and various objects from professor Košćec legacy. Among them, tools can be seen which he himself created to help him work on his collection.
Other natural scientists from Varaždin who lived and worked here at the end of the 19th and the beginning of the 20th century are also portrayed as a part of the permanent exhibition and one of the rooms has been decorated as professor Košćec' study.
Since the beginning of 2008 the department has introduced some novelties in this field, namely a part of the exhibition intended for blind and weak sighted people under the name Perception by touch.