Oliver Erichson Janson was an English

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 entomologist who specialised in Coleoptera.

He was the son of Edward Wesley Janson

Edward Wesley Janson

Edward Wesley Janson was an English entomologist who specialised in Coleoptera.The Janson family was of Dutch origin and Edward Wesley Janson's father was the London Agent of the Dutch-Rhenish Railway Company....

 and took over the family natural history and publishing business.
Janson's early years were spent at Fortis Green

Fortis Green

Fortis Green is a ward in the extreme north-western corner of the Borough of Haringey, North London. It is also the name of the road that runs between Muswell Hill and East Finchley which forms part of the A504....

, and he collected beetles there and at Finchley

Finchley

Finchley is a district in Barnet in north London, England. Finchley is on high ground, about north of Charing Cross. It formed an ancient parish in the county of Middlesex, becoming a municipal borough in 1933, and has formed part of Greater London since 1965...

, Hampstead

Hampstead

Hampstead is an area of London, England, north-west of Charing Cross. Part of the London Borough of Camden in Inner London, it is known for its intellectual, liberal, artistic, musical and literary associations and for Hampstead Heath, a large, hilly expanse of parkland...

 and Highgate

Highgate

Highgate is an area of North London on the north-eastern corner of Hampstead Heath.Highgate is one of the most expensive London suburbs in which to live. It has an active conservation body, the Highgate Society, to protect its character....

.
In 1906 he made an expedition to Iceland

Iceland

Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

 adding to the collections of the National Museum of Iceland

National Museum of Iceland

The National Museum of Iceland was established on 24 February 1863, with Jón Árnason the first curator of the Icelandic collection, previously kept in Danish museums...

During the First World War he made three trips to Ireland, particularly Co Kerry.
Janson was a world authority on Cetoniinae publishing new genera and species mostly in Cistula Entomologica published by Janson and Co.
His world collection was purchased by Titus Valck Lucassen. His collection, in turn, was acquired by the Rijksmuseum van Natuurlijke Historie

Rijksmuseum van Natuurlijke Historie

The Rijksmuseum van Natuurlijke Historie was a museum in Leiden, The Netherlands. It was founded in 1820 by Royal Decree, formed from a merger of several existing collections. This happened at the instigation of Coenraad Jacob Temminck, who saw the museum primarily as a research institute...

 at Leiden in 1940.

He was a Fellow

Fellow

A fellow in the broadest sense is someone who is an equal or a comrade. The term fellow is also used to describe a person, particularly by those in the upper social classes. It is most often used in an academic context: a fellow is often part of an elite group of learned people who are awarded...

 of the Royal Entomological Society.

Works

Partial list

Coleoptera

• Descriptions of three new species of American Cetoniidae. Cistula Entomologica. 1:373-376 (1875).
• Notices of new or little known Cetoniidae. Cistula Entomologica. 2:133-140 (1876).
• Descriptions of new American Cetoniidae, Part 2. Cistula Entomologica. 2:581-585 (1881).
• Notices of new or little known Cetoniidae. Cistula Entomologica. 3:139-152 (1885).
• On the male sex of Argyripa subfasciata Rits., and description of a new species of the cetoniid genus Allorhina. Not. Leyden Mus. 10:118-120(1886).

Lepidoptera

• Notes on Japanese Rhopalocera with the description of new species Cistula ent. 2 : 153-160 (1877)
• Descriptions of two new eastern Species of the genus Papilio
  Papilio
  Papilio is a genus in the swallowtail butterfly family, Papilionidae. The word papilio is Latin for butterfly.The genus includes a number of well-known North American species such as the Western Tiger Swallowtail...
  
  Cistula ent. 2 (21) : 433-434, pl. 8 (1879)