CHAPTERAXX 
PENTASTOMIDA ! 
OCCURRENCE—-ECONOMIC IMPORTANCE—-STRUCTURE— 
DEVELOPMENT AND LIFE-HISTORY—SYSTEMATIC 
PENTASTOMIDS are unpleasant-looking, fluke-lke or worm-like 
animals, which pass their adult lives in the nasal cavities, 
frontal sinuses, and lungs of flesh-eating animals, such as the 
Carnivora, Crocodiles, and Snakes; more rarely in Lizards, Birds, 
or Fishes. From these retreats their eggs or larvae are sneezed 
out or coughed up, or in some other way expelled from the 
body of their primary host, and then if they are eaten, as 
they may well be if they fall on grass, by some vegetable-feeding 
or omnivorous animal, they undergo a further development. If 
uneaten the eggs die. When once in the stomach of the second 
host, the egg-shell is dissolved and a larva emerges (Fig. 260, 
p. 494), which bores through the stomach-wall and comes to rest in 
a cyst in some of the neighbouring viscera. Here, with occasional 
wanderings which may prove fatal to the host, it matures, and 
should the second host be eaten by one of the first, the encysted 
form escapes, makes its way to the nasal chambers or lungs, and 
attaching itself by means of its two pairs of hooks, comes to rest 
on some surface capable of affording nutriment. Having once 
taken up its position the female seldom moves, but the males, 
1 The animals included in this group are usually called Linguatulidae or 
Pentastomidae after the two genera or sub-genera Linguatula and Pentastoma. 
But the animal which Rudolphi in 1819 (Synopsis Hntozoorwm) named Pentastoma 
had been described, figured, and named Porocephalus by Humboldt (Recueil 
d@ observations de zoologie et anatomie comparee, i. p. 298, pl. xxvi.) in 1811. The 
familiar name Pentastoma may, however, be preserved by incorporating it in the 
designation of the group. 
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