3 5 6 
The Two-winged Flies 
horse, cow, sheep, etc., as well as birds. The male jigger-fleas hop on or 
off the host as other fleas do, but the females, when ready to lay eggs, burrow 
into the skin, especially that of the feet, and produce a swelling and later 
a distinct ulcer, sometimes so serious as to result fatally. The remedy is 
(as also for the chigger-mite) the pricking out entire, with a needle or knife¬ 
point, of the pest as soon as its presence is detected. The bursting of the 
body of the female in the skin, with the release of its eggs, is likely to result 
seriously. When domestic animals are attacked it is difficult to fight the 
pest. The liberal use of pyrethrum on the rubbish or dust in which the 
young stages are developing is recommended. The hen-flea, Xestopsylla gal- 
linacea , first described from Ceylon, sometimes becomes a serious pest of 
fowls in warm regions. The females of the hen-flea burrow into the skin of 
the fowl and lay their eggs in the small tumor which forms about them. 
This pest has been known in the Southern United States since about 1890 
and is a common pest from Florida to Texas. 
The second family, Pulicidae, includes all the other fleas, none of which 
burrows into the skin. The various species range in size from ^ inch ( Anomi - 
opsyllus nudatus , found on a mouse in Arizona) to J inch ( Ceratophyllus 
stylosus, taken from Haplodon in Oregon), but all fairly similar in shape 
and appearance to the familiar house-fleas. They are grouped in nine 
genera, of which Pulex is much the largest and includes the human flea 
and the cat- and dog-flea, the two species to which the house-infesting pests 
belong. The human flea, Pulex irritans , was described by Linnaeus in 
1746. It is known all over the world, and often becomes a serious pest. 
In this country it is probably not so commonly met with in houses as the 
cat- and dog-flea, Ctenocephalus canis , from which it may be readily dis¬ 
tinguished by its lack of combs of spines on the back of the head and 
prothorax. The eggs of irritans “are deposited in out-of-the-way places, 
in the dust or lint under carpets, and the larvae are said to feed upon the 
particles of organic matter which may be found in such localities.” Raillet 
states that each female deposits eight to twelve eggs from which larvae hatch, 
in summer, in from four to six days, become pupae eleven days later, and 
after about twelve days in this stage become adult. In winter, in warmed 
houses, the whole development takes about six weeks. The cat- and dog- 
flea lays its eggs on or among the hairs of an infested animal, but the 
eggs drop to the floor or ground as the animal moves about, and the larvae 
live in the dust, feeding on whatever bits of organic substance they can find 
there. Larvae placed on dust with birds’ feathers mixed with dried blood 
developed perfectly. Others put on the sweepings of a room developed 
as well. These fleas are especially abundant and troublesome in houses 
in the East in damp summers. As flea-larvae will not develop successfully 
in places where they are often disturbed, much sweeping and scrubbing 
