One of the first British naturalists to have taken a serious interest in beetles. He was born in Somerset and subsequently educated at St. Paul's School and at Queen's College, Cambridge where he took a degree in Medicine (15 April 1688). By 1692 he had established himself as a Doctor at Braintree, Essex and it was there that he met John Ray who subsequently became a life-long friend, and Samuel Dale, the botanist.
It would seem that it may have been Allen's interest in Lampyridae which first brought him into contact with Ray for in a letter to Sir Tancred Robinson of 8 July 1692 Ray wrote: ‘1 doubt not but that they are everywhere to be found, being nothing else but a kind of long-bodied beetle ... The reason why I mention this is because this gentleman [Allen], meeting with this beetle and finding by strict observation that the body of it answered exactly in figure to that of the creeping glow worm, suspected it to be the male glow worm; and, having some creeping glow worms by him, put this animal into a box with one of them; which after some short time, coupled with it.’
Nearly twenty years later Allen published his own account of this experiment in The Natural History of the Mineral Waters of Great Britain to which are added some Observations of the Cicindela Glow Worm, London, 1711. Allen also published another work concerning beetles entitled 'An Account of the Scarabaeus Galeatus Pulsator or Death Watch' in Phil.Trans.R.Soc, xx, 1699, 376-8. In this he recorded that in August 1695 he took two of the beetles and that he kept them for several days for observation. He describes them in minute detail, ridicules the common idea of the noise foretelling death, and illustrates his description with three figures one of which was 'drawn with the help of the microscope'. (Is this the first record of someone using a microscope to study beetles?)
Two manuscript Common Place Books in the collection of the Royal College of Surgeons contain amongst medical and other information several hundred pen sketches of 'insects' (a term used by Allen in a very wide sense, he includes, for example, that well known 'insect' the Oyster!) amongst which are more than fifty drawings of beetles. There are two excellent accounts of him by Miller Christy in Essex Naturalist (1910: 145-75 and 1912, 17: 1-14). Allen is buried alongside Ray in the churchyard at Black Notley, Essex. (MD 7.01, 9/22)