86 Acarology 



23. Radfordiella Fonseca, 1948 



Type. Radfordiella oudemansi Fonseca, 1948 



24. Steatonyssus Ko\cn2Li\, \^5d, 



Type. Acarus musculi Schrank, 1803 



Discussion: Dermanyssids typically have a larval and two nymphal 

 stages before becoming adult males and females. They are parasitic on 

 vertebrates and are of considerable economic and medical importance. 

 The family is frequently subdivided into two subfamilies, the Derma- 

 nyssinae with needle-like chelicerae, and the Liponissinae with more 

 normal chelicerae. Only three genera — Dermanyssiis, Liponyssoides, 

 and Allodermanyssiis — are included in the Dermanyssinae. Some au- 

 thors have given familial standing to the two groups. Fonseca 1948 

 has written a monograph of those genera that are sometimes included 

 in the Liponissinae or Liponissidae. He, however, refers to the group 

 as the Macronyssidae. The arrangement of the genera presented here 

 is based largely on Fonseca's 1948 monograph, Vitzthum 1941, and 

 the advice of R. W. Strandtmann in litt. The Dermanyssidae are as yet 

 poorly known so that the present picture must still be considered as 

 tentative. 



Dermanyssus gallinae (DeGeer, 1778) is an important pest of 

 domestic birds, especially chickens and pigeons, in all parts of the 

 world. Heavy infestation with these mites can cause the death of their 

 hosts, while light infestations result in reduced egg production and 

 poor growth. The mites normally feed at night and infest the host only 

 at this time. During the day they are found in the cracks of roosts, 

 coops, and nests. At times they may be so numerous in nests that 

 brooding hens will leave their eggs. D. gallinae will also attack man, 

 especially children. A family in Durham, North Carolina, complained 

 of a severe dermatitis on their baby. The mother and father were not 

 affected. Examination of the house revealed numerous specimens of 

 D. gallinae on an electric clock in the living room. The clock was 

 slightly warmer than the rest of the room and it is probable that the 

 mites were attracted to it for this reason. The gutter on the roof of the 

 house was used extensively by pigeons and their droppings had col- 

 lected in a great pile on the roof of the porch. After removal of 

 the droppings and elimination of the pigeons the mites disappeared 

 and the child was no longer bothered. Recently the virus of St. Louis 

 encephalitis has been recovered from chicken mites and it is suggested 

 that D. gallinae serves as a reservoir for the disease (M. G. Smith et 

 al. 1948). As more and more work is done on the epidemiology of 



