78 



REPORT 108, U. S. DEPARTMEXT OF AGRICULTURE. 



an affection of the surfaces attacked by them, since they have usually been discovered 

 when the host has died from some disease of the air passases. It is possible that the 



apparent relationship of these two q:enera is a 

 case of convergence due to the peculiar nature of 

 their habitat. 



The Dermanyssinse are in general very similar 

 to the Parasitinse, and in the weakly chitinized 

 shields covering only part of the dorsum and the 

 unarmed jaws present the most prominent differ- 

 ences. Several authors cite their parasitic habits 

 as a distinguishing character, but we now know 

 so many species of true Parasitinse (as Laelaps) 

 that also occur on animals that it is doubtful if 

 the group can be maintained distinct from the 

 Parasitinse. 



The genus Haemogamasus (fig. 149) appears to 

 belong to this group. It occurs on moles in Ger- 

 many and Italy; the legs are very slender, the 

 hind tarsi being as long as the width of the body. 

 There are thi'ee other genera, which may be tab- 

 ulated as follows: 



1. Vulva longitudinal; occurs on snakes. . 



Ophionyssus. 



A^ilva transverse 2 



2. Mandibles in both sexes chelate. .Liponyssiis. 

 Mandibles in the male chelate; in the 



female long and styliform Dermanyssus, 



The only known species of Ophionyssus has been 

 taken on snakes in southern E.urope. The species 

 of Lipomjssus (figs. 147, 148) (formei'ly known as Leiognathus) are parasitic on mice, 

 rats, bats, and related small mammals. Several species are known from the United 

 States and Canada. They also occur in the nests of these 

 mammals. In general appearance they resemble the spe- 

 cies of Dermanyssus. Gonder (1909) claims that a trypano- 

 some of bats is spread by Liponyssus arcuatus Koch. A 

 species of Liponyssus (L. bacoti Hu'st) has been found bit- 

 ing people in stores and factories in Australia; it also oc- 

 curs on rats in Africa and South America. The species 

 of Dermanyssus occur on birds, especially those kept in 

 domestication. D. gallinae Redi (figs. 145, 146) is a serious 

 pest to poultry in many parts of the country. They hide 

 in cracks and crevices by day, but at night crowd upon the 

 fowls and suck their blood. They are more injurious in 

 the Southern States than elsewhere. Sometimes they 

 attack man and cause itching and soreness. Chickens 

 endeavor to get rid of the mites by a dust bath, but when 

 the mites are numerous it will be best to spray or wash the 

 henhouse with kerosene, benzine, or gasoline. White- 

 washing with carbolated lime will destroy a great many 

 of them. If the ends of the roosts are daubed with coal 

 tar the mites will be unable to reach the fowls. A mix- 

 ture of kerosene and sulphur plastered upon the roosts 

 and in bottoms of the nests is also very useful. Sulphur 

 flour sprinkled in the nests will also aid in destroying the pesls. They breed very 

 rapidly, and if an infested jioultry house is not treated in the spring they will make 



Fig. lid.—naemogamams americari'is, and 

 anal plate. (Author's illustralion.) 



Fig. 150.— Rhodocarus roseus, 

 dorsal and ventral a^iwcts. 

 (Original.) 



