The parasites of snakes are here enumerated by Dr. L. W. Sambon, in systematic order.
Arthropoda.—Two families of the class Arachnida, the Ixodidæ and the Linguatulidæ, furnish numerous species parasitic on snakes.
Of the Ticks (Ixodidæ) we find, as a rule, species of the genera Amblyomma and Aponomma, the latter genus being almost entirely confined to Reptiles. A single species of the genus Hæmaphysalis (H. punctata, Can. and Franz, 1877) has been reported once from Vipera aspis. A few larval forms found on various snakes have been reported under the generic name Ixodes, but they probably belong either to Amblyomma or Aponomma.
The Ophidian Tick-parasites, like those of mammals, birds, lizards, and tortoises, appear to be in many cases the means of transmission of protozoal infections from snake to snake.
The Tongue-worms (Linguatulidæ) are, without doubt, of the greatest possible interest. Their systematic position has ever been a puzzle to zoologists, and even now is a matter of controversy. They have been looked upon as Hirudinea by Winsberg (1765), Cestoda by Chabert (1787), Acanthocephala by Humboldt (1808), Trematoda by Rudolphi (1809), and Nematoda by Nordmann (1832). It was Van Beneden (1848) who first recognized their Arthropod nature, but he placed them amongst the Crustacea. Schubärt (1853) suggested that their proper position is amongst the Mites (Acarina), and Leuckart (1860) adduced important anatomical and embryological evidence in support of this view, which was confirmed by Railliet in 1883 and by Sambon in 1910.
No less than three out of the four genera of Linguatulids so far established are represented by species parasitic on snakes. They are the genera Porocephalus, Reighardia, and Raillietiella.
The genus Porocephalus is of special interest, because some of its species, such as Porocephalus armillatus, a parasite of African Pythons (Python regius, P. sebæ) and Puff-adders (Bitis arietans, B. nasicornis, B. gabonica), and Porocephalus moniliformis, a parasite of Oriental Pythons (Python molurus, P. reticulatus), are, in their nymphal stage, deadly parasites of mammals, including man.
The genus Reighardia was established by Professor H. B. Ward, in 1899, for a Linguatulid of gulls and terns, first described, in 1861, by De Filippi. In 1910 Sambon included in this genus other similarly structured Linguatulids from crocodiles, monitors, and snakes.
The genus Raillietiella was established by Sambon in 1910 for a Linguatulid (Raillietiella boulengeri) of the African Puff-adders (Bitis arietans, B. gabonica). Amongst the characters of this genus is one of great structural and phylogenetic importance—viz., the position of the female sexual orifice at the anterior end of the abdomen, whilst in the other known genera it is at the posterior extremity.
According to Prowazek, Sambon, and Laveran, the Ophidian Linguatulids, which live as blood-suckers in the air-passages of their hosts, are able to foster and transmit the hæmogregarines of these hosts.