INTRODUCTION. 
CoMPARED with the work that has been done in Europe upon the Arachnida Acaridea 
from the time of the classical writers, Linneus, De Geer, Hermann, and Latreille, 
up to that of Dugés, Koch, Nicolet, P. Kramer, Mégnin, Michael, Neuman, Berlese, 
Canestrini, Nalepa, and many others, the American literature of this group of animals 
is exceedingly scanty. Thomas Say (1821), one of the first entomologists in the 
United States, paid some attention to this neglected group. Later on (1836), 
Dana and Whelpley, as well as Haldeman (1842), described and figured some North- 
American species of Hydrachnide. In our times we meet with the well-known names 
of Riley and Packard in connection with North-American Acarids of various groups, 
and Mr. Harry Garman has published a paper on the Phytoptide. In 1886, Messrs. 
Herbert Osborn and Lucien M. Underwood gave a “ Preliminary List of the Species 
of Acarina of North America” in the ‘Canadian Entomologist.’ In Mexico, M. Alfred 
Dugés has published several valuable articles on various species of Acarids inhabiting 
that country, and M. Conil in Buenos Ayres has done the same for some species of the 
Argentine Republic. 
A certain number of American Acaridea have been described by European authors, 
and some of the larger and more conspicuous species were already known to the 
founders of Entomology, to Linnwus, De Geer, and Fabricius. In modern times 
C. L. Koch has described several Ixodide from various parts of America, and Trouessart 
and Mégnin have studied some forms of Dermaleichide which live on American birds. 
‘To Antonio Berlese and R. Canestrini we are indebted for some most valuable papers 
on Acaridea from the La Plata region and from Brazil. 
But nevertheless we are far from possessing a knowledge of the American Acarid 
fauna comparable to that which we have long had of the European forms. 
In the following pages an attempt has been made to fill, to some extent, the gap 
which at present separates the forms known from North America and those described by 
