60 LIFE HISTORY OF NORTH AMERICAN TICKS. 
fourth molt before arriving at the adult stage, 9 or more days (869° F. 
of effective temperature) being required for the ecdysis. The first — 
adult engorgement then takes place, and following copulation eggs 
are deposited. Unlike the ticks of other genera, with the exception 
of some species of Ornithodoros, these ticks engorge a number of 
times as adults, and each engorgement is usually followed by ovi- 
position. The eggs may hatch in summer as soon as 10 days, 437° F. 
of effective temperature being required for their incubation. 
ECONOMIC IMPORTANCE. 
In parts of the southern United States this tick 1s the most impor- 
tant ectoparasite of fowls, though perhaps surpassed in some locali- 
ties by some of the insect pests. It is frequently referred to as the 
‘blue bug”’ because of the bluish color when engorged with blood. 
In Brazil, Martinique, India, Soudan, Transcaucasia, and South 
Australia a disease of fowls known as spirochetosis is transmitted 
by this species. The presence of this disease in the United States 
has not been demonstrated, but on account of the losses due to the 
tick as a parasite in certain sections of Texas, poultry raisers in some 
cases have entirely abandoned the business. It has been found that 
the spirochete virus when imbibed will remain virulent within the 
tick during a period of six months fasting. Dodd (1910), who has 
recently studied the disease in Australia, reports that in one instance _ 
a fowl which was bitten by ticks that had fasted for 7 months and6 — 
days died with symptoms of chronic spirochetosis. 
Lounsbury, who has permitted specimens of Argas miniatus and 
Ornithodoros savignyt to feed upon his arm, concludes that while 
they may be productive of considerable irritation and their penetra- 
tion serve as the entering point for some of the abscess-forming bac- 
teria, as may be said of all the ticks, yet otherwise their direct effect . 
is harmless. Nuttall and Strickland (1908) have found that the 
salivary glands and intestines of the fowl tick contain anticoagulin, 
but no hemolysin. 
NATURAL CONTROL. 
The habits of this tick are such as to protect it from natural ene- 
mies, although it is undoubtedly fed upon by rats and mice and 
devoured by fowls. To determine the effect of water upon it, 25 
larvee which had hatched on September 1 were submerged on Sep- 
tember 9 and kept so for 174 hours, during all of which time they 
remained inactive. When removed from the water all proved to be 
alive and were again submerged and left until a total period of 654 
hours had elapsed. One survived and lived for about two weeks 
following removal from the water. Thirteen larve which had hatched 
several days previous were submerged on September 12 for a period 
of 50 hours and none survived. 
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