278 INSECTS AND MAN 



many other blood-sucking insects, ejects a drop of blood 

 from the rectum during feeding operations. Experiment 

 shows that this ejected faecal matter is frequently highly 

 charged with disease germs, hence it is a probable source 

 of infection. 



A frequent though not a specific parasite of man is the 

 jigger flea or Chigoe, Dermatophilus penetrans. Natives of 

 South America, these fleas were introduced into Ambiez, in 

 the south of the Congo, forty or more years ago, by a ship 

 from Brazil, and they were supposed to have been taken to 

 the great lake regions by Stanley's expedition. 



The jigger fleas are more truly parasitic than the true 

 fleas, for the female jigger embeds herself beneath the skin 

 of the host, forming a kind of pocket, in which to carry 

 out part of her life. Both male and female are small and 

 live upon blood. After mating, the female seeks a host, 

 into whose skin she may burrow ; often a human being is 

 selected, though pigs, dogs, mice, and other animals may 

 all fall victims to this insect. Some soft portion of the 

 host's anatomy is selected for operations, and a favourite 

 situation is the skin beneath the toe nail. A suitable 

 place having been found, the female jigger perforates the 

 skin and works her way beneath the surface so far that 

 only the tip of her abdomen projects. Within this hiding- 

 place her body swells to the size of a pea (fig. 78), and in 

 this state the segmentation of the abdomen is completely 

 lost, even the head and thorax being visible only with the 

 help of a lens. Needless to say, this increase in size, due 

 to the formation of eggs, causes a considerable amount of 

 suffering to the host, and in some cases death ensues. 

 After a while the eggs are laid, to the number of about one 

 hundred, not within the host but outside, and this is the 

 reason for the female jigger leaving the tip of her abdomen 

 exposed. The larvae are very similar to those of the 

 human flea, but they are to be found in dry, sandy places, 

 rather than in houses. 



