The Arachnida collection of the NMNHS is over 120 years old and includes faunistic materials presenting all arachnid orders of the world. The richest in the country (and in the Balkans as a whole) collection of spiders of the former Institute of Zoology, which has been developed by Dr Christo Deltshev for nearly 50 years, is currently kept in the museum. The collection was started by Dr Pencho Drensky and comprises faunistic materials collected on the territories of Bulgaria, Greece, North Macedonia, Serbia, Turkey, Turkmenistan, Morocco, Papua New Guinea, China, Vietnam, Indonesia, Laos, Tunisia etc. The faunistic materials from outside the Balkan Peninsula have been collected mainly by Dr Petar Beron, who significantly expanded the Acari collection of Drensky. Representative are Sarcoptiformes and Parasitiformes collections and 112 type specimens are designated. The collections from Scorpiones, Pseudoscorpiones, Opiliones, Solifugae, Amblypygi, Uropigi, Schizomida, and Ricinulei were also created and curated by him. The depot was renovated in 2013.