The Regent's Park's diverse grassland, woodland and wetland habitats together support 21 species of butterfly and more than 230 species of moth. Some unusual butterfly records for the area include the Marbled White and the White Letter Hairstreak.
A nice species to look out for is the Holly Blue - a small but distinctive powder-blue species that has two generations per year. Remarkably, the first generation breeds mainly on Holly in the spring and the second depends exclusively on Ivy in the summer.
The planting of reed beds around the Boating Lake has had many ecological benefits, improving water quality and providing habitat for birds and invertebrates such as the several species of Wainscot moth. These waterside areas are also attractive to dragonflies and damselflies and at least 9 species have been recorded.
There are many other invertebrates that also benefit from the careful management of the park's habitats. In 2003 a survey of The Regent's Park and Primrose Hill reported a total of 104 different spider species for the sites (including 6 of national importance) and 109 species of beetle (including 4 of national importance).