More than 70 years after he began compiling a colossal collection of 20,000 insects, a Grange-over-Sands entomologist has presented his life's work to a Carlisle museum.

After spending hour-upon-hour scouring the marshes, mosses and moors of South Lakeland for various specimens and a number of rare, and now extinct examples, retired GP Neville Birkett has handed over his hoard to Tullie House because of failing eyesight.

The 87-year-old explained a school friend got him hooked on the hobby in 1931. "I became interested as a boy when a friend showed me his wonderful collection, and over the years I have found all sorts of different species in various local places."

Using butterfly nets and light traps, Dr Birkett who is president of Kendal Natural History Society explained he had found and bred the majority of his collection, which includes moths, butterflies, beetles and flies. It also features a silver-studded blue butterfly a species that is now extinct.

"In the 1950s I started using nets and traps which produce a large number of moths. I would also go round hunting for caterpillars which I could then breed through," he said.

"Leighton Moss and Arnside Knott are both favourite areas where I have found a lot of variety and a number of rare examples but it is a very specialised collection. Tullie House has good collections from the north of the county and mine is based around southern Cumbria so the museum was very pleased and keen to receive this addition."

The museum's keeper of natural sciences, Stephen Hewitt, said he was "delighted" to be given the collection.

"The collection is made up mostly of moths and butterflies but there are a number of flies and beetles and some rare examples Dr Birkett has done a great deal of work.

"It is a valuable addition because it features rare examples such as a stilt bug, found in the 1970s, which had only previously been found in the south. This, for instance, provides us with information on how climate changes are causing the species to spread northwards. There is also a silver-studded blue butterfly, which was found at Morecambe Bay - these became extinct in the 1940s.

"This fabulous collection is a significant addition to the museum and complements our own collections very well."

Members of the public can view the reference collection by appointment. Call Tullie House Museum on 01228-534781.