THE NORTH AMERICAN CATTLE TICK. 111 
were parasitized, 67 produced adult ticks (27 males and 40 females), 
and 6 did not produce either ticks or parasites. Of the 100 collected 
at Corpus Christi, 40 were parasitized, 53 produced adult ticks (20 
males and 33 females), and 7 produced neither ticks nor parasites. 
Although a number of lots of nymphs have been collected which 
have shown no signs of parasitism, the insect is undoubtedly an impor- 
tant enemy of this tick. The parasite appears to be more restricted 
in its distribution in the United States than is the tick. Recently 
Mr. C. W. Howard has reared this an in Portuguese East 
Africa from the same host.* 
ARTIFICIAL CONTROL. 
Spraying frequently with, or dipping in a solution of one of the sev- 
eral coal-tar products that are now on the market should be practiced 
when this tick becomes a pest. It is important that the kennels or 
other sleeping places of dogs be kept scrupulously free from filth and 
that they be thoroughly sprayed at frequent intervals with some 
strong disinfectant. The destruction of roving and uncared-for dogs 
also greatly aids in the control of this tick. 
Genus MARGAROPUS Karsch. 
Of all the ticks those belonging to the genus Margaropus are the 
most important economically, owing to the part which they play in 
the transmission of Piroplasma and Anaplasma, which cause splenetic 
fever in bovines. Neumann recognizes 5 varieties of annulatus, all of 
which appear to transmit piroplasmosis. In addition to annulatus, 
we have studied the variety australis. One variety, decoloratus, 
is known to transmit Spirochexta theileri, which is the cause of a disease 
of cattle in South Africa. All of the ticks of this genus pass both 
molts upon the host. 
THE NORTH AMERICAN CATTLE TICK.? 
Margaropus annulatus (Say). 
The common name of this species comes from the fact that it is 
the most common and important tick attacking cattle in North 
America. 
DESCRIPTIVE. 
Adult (Plate VIII, figs. 1, 6-11).—Males from 2 by 1.25 mm. to 
2.4by1.3mm. Females, unengorged, about 3 by 1.75 mm.; engorged, 
iia 10.5 by 6 by 4.5 mm. to 14 by 9 by 6 mm. 
Nymph (Plate VIII, figs. 3-5)—Unengorged, about 1.5 by 0.6 
mm.; engorged, about 3 by 2.8 by 0.8 mm. Salar. unengorged, light 
1 More recent studies of this parasite have been published by Wood (1911). 
2 The data on the cattle tick are presented in order that its biology may be compared with that of the 
other ticks. For more detailed information see Bulletin 72 of this bureau. The discovery of the fact that 
Dermacentor venustus conveys the infection of Rocky Mountain spotted fever has made it desirable that 
the above name be applied in place of that of North American fever tick, used in Bulletin 72. 
