THE POLEX IRRITANS. 385 
sometimes twice or three times larger than usual, are found upon 
the shores frequented by bathers, but they are of the same kind 
as that which attacks the human race. Fleas lay their eggs in 
cracks, in cushions, and in boards, or in the midst of dust, and 
their larva, which have no legs, and which, therefore, must live 
where they have been born, can only exist in consequence of 
the nourishment brought to them by the adults. Were they 
abandoned they would perish, but they have excellent mothers 
who never leave them; for after a flea, should it be a mother, 
has gorged itself with blood it seeks its young and disgorges a 
small quantity so as to keep them alive. 
THE METAMORPHOSES OF THE COMMON FLEA. (Litlex irritans.) 
The larva shut themselves up in silken cocoons when they 
have attained their full size, and undergo their metamorphosis 
into the condition of nymphs. In the engraving the long, legless, 
vermiform larva may be seen close to an inactive nymph, which 
resembles somewhat the perfect insect, which has long legs and 
the peculiar hairiness of the segments. The dog’s flea (Puzzler 
canis) is smaller than the species which attacks man, and is 
distinct from it, nevertheless it sometimes interferes with human 
beings. The Jigger, or Puler penetrans, which lives in the hot 
districts of America, introduces itself under the skin of men and 
animals, and grows there to a surprising size; it is very small 
when it is born. The male always retains its tiny size, and does 
not shut itself up for life; but the female attains an immense 
size when underneath the skin, growing sometimes as large as a 
nut, on account of the dilatation of the abdomen by the abundance 
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