THE DERMANYSSID MITES OF NORTH AMERICA. 
By H. E. Ewine, 
Of the Bureau of Etomology, United States Department of Agriculture. 
INTRODUCTION. 
The Dermanyssid mites are here regarded as constituting a family, 
the Dermanyssidae, of the superfamily Gamasoidea.!’ They were so 
recognized, in a broader sense by Banks (1904), but later (1915) Banks 
reduced the group to the rank of asubfamily. His former decision 
in the matter will appear, the writer believes, amply justified when 
the unity of the group and its possibilities of division into various 
genera are considered. 
The family Dermanyssidae is characterized as follows: Mouth parts 
adapted for piercing, the chelicerae being either devoid of one or both 
of the chelae or of all true teeth; but, however, recurved “holdfast”’ 
hooklike structures are sometimes present. Integument somewhat 
leathery and distensible, but covered to a large degree by one or more 
dorsal shields and one or more ventral ais. Each trachael trunk 
opening through a peritreme situated on the side of the body. Sexual 
dimorphism evident and at times marked. Parasitic in habits and 
on vertebrates. 
Using the mouth parts as a basis, we can easily divide the family 
into four major groups, which are here given the rank of subfamilies. 
These subfamilies and their contained genera are separated as follows: 
KEY TO THE SUBFAMILIES AND GENERA OF DERMANYSSIDAE. 
a‘. Chelicerae adapted for both piercing and attachment, being provided with 
recurved barbs or hooks. 
b'. Both chelae of chelicera present, the fixed one harpoonlike witha single 
,tecurved barb and the movable one falciform; hypostome without recurved 
| Eg] S tS Ra a ln ca al Tie ENTONYSSINAE, new subfamily. 
Containing but one genus..................... Entonyssus, new genus. 
b?. One chela of chelicera lost, the remaining one provided with several recurved 
hooks; hypostome with a pair of recurved hooks. 
Subfamily IXODORYNCHINAE, new subfamily. 
Containing but asingle genus............... Ixodorhynchus, new genus. 
1 According to the Pres of nomenclature it may be necessary to change the name of the type genus 
of this group to Parasitus. To doso, however, is most unfortunate not only because the name Gama- 
sidae has been established by a century of usage but also because the name Parasitus is applied to free- 
living mites, hence is directly misleading in its meaning. 
No. 2459—PROCEEDINGS U. S. NATIONAL MUSEUM, VOL. 62, ART. 13 
