THE chigoes and their allies belong to a group of fleas sufficiently remarkable to deserve a somewhat detailed account. The reader may remember that they form a family to which the name of _Sarcopsyllidæ_ has been given. They are the most completely parasitic of any fleas; and the South American chigoe (_Dermatophilus penetrans_) enjoys the distinction of being the first foreign flea ever described. This pestilent insect, of which the female has the habit of burrowing into the flesh of the host, soon made itself known to the early travellers in the tropics of America. Oviedo, the Spaniard and historiographer of South America, in his _Historia General y Natural de las Indias_ (1551), seems to have been the first European author who mentions it. After this the chigoe is referred to by writers of various nationalities in many works which were published during the sixteenth, seventeenth and eighteenth centuries. It is an insect which appears under a vast number of different names: chigoe, chigue, chego, chigger, chique, jigger, pico, sico, migua, nigua, ton, and tschike are synonymous. Catesby in his _Natural History of Carolina_ (1743) gives a figure of the insect, which is easily recognisable. Linnæus, in 1758, described the chigoe as _Pulex penetrans_, and apparently did not know much of its appearance beyond what he learnt from Catesby’s picture. This species and the human flea were the only two which the great Swedish naturalist distinguished by a name; though, under the title _Pulex irritans_, he includes a number of different species such as the fleas from the dog, cat, rabbit and fowl. The chigoe remained the only member of the family known to scientific entomologists until the year 1860. An allied insect was then found on a South American parrot. A third member of the family was soon after discovered, and is noteworthy because it was the first species recorded from the Old World. It is now known to infest the domestic fowl in all warm countries where these birds have been introduced by man. A fourth species was collected from a South American bat. Up to the present time some fourteen different species (belonging to three very distinct genera) have been described, and there cannot be the slightest doubt that, when collectors in hot countries turn their attention to the matter, a great many other forms of this interesting family of fleas will be found.