The True Chiggers 
127 
why it should not become established in Florida and Texas. It is 
usually believed that Brazil was its original home. Sometime about 
the middle of the nineteenth century it was introduced into West 
Africa and has spread across that continent. 
The males and the immature females of Dermatophilus penetrans 
(fig. 93) closely resemble those of other fleas. They are very active 
little brown insects about 1-1.2 mm. in size, which live in the dust of 
native huts and stables, and in dry, sandy soil. In such places they 
often occur in enormous numbers and become a veritable plague. 
They attack not only man but various animals. According to 
Castellani and Chalmers, “Perhaps the most noted feature is the way 
93. Dermatophilus penetrans. Much enlarged. After Karsten. 
in which it attacks pigs. On the Gold Coast it appeared to be largely 
kept in existence by these animals. It is very easily captured in 
the free state by taking a little pig with a pale abdomen, and placing 
it on its back on the ground on which infected pigs are living. After 
watching a few moments, a black speck will appear on the pig’s 
abdomen, and quickly another and another. These black specks are 
jiggers which can easily be transferred to a test tube. On examina¬ 
tion they will be found to be males and females in about equal 
numbers.” 
Both the males and females suck blood. That which characterizes 
this species as distinguished from other fleas attacking man is that 
when the impregnated female attacks she burrows into the skin 
and there swells until in a few days she has the size and appearance of 
a small pea (fig. 94). Where they are abundant, hundreds of the 
