The majority of the invertebrate collection is made up of insects c.50,000 and molluscs c.65,000.
- Butterflies: approximately 3,000 specimens including a large packeted collection of Indian species. A number of cased exotics transferred from Darlington.
- Moths: a large collection of UK moths, especially micro moths.
- Spiders: large spirit collection from local surveys carried out in the former County region of Cleveland during the 1970ís. Report available.
- Beetles: a large 19th. century collection of world wide specimens acquired around 1934, possibly part of the collections of Alexander Fry (1821-1905).
- Other groups represented by just a small number of specimens in mixed collections, some relating to the 1970's surveying.
- Tropical molluscs: around 65,000 specimens including part of the J.H. Fryer collection (also in Hancock Museum); G.L. Dorman collection and others. Mostly 19th century and requiring further documentation work.
- UK molluscs: large collection of fresh water and land molluscs collected by Baker Hudson and Rev. John Hawell, mostly local, late 19th century and early 20th. century. Mostly very local.
- Corals & sponges: about 200 tropical specimens.
- Others: small collections of crustacea, echinoderms etc. Also some early 20th century large scale plaster models.