184 FLEAS, FLUKES AND CUCKOOS 



which is also recorded from seals and fish, parasitises a wide variety of 

 birds in Britain. P. depressum uses moles and shrews as second inter- 

 mediate host and birds of prey, such as the peregrine falcon and tawny 

 owl, as the final host. 



Chickens harbour a nematode in their eye, another in their crop, 

 stomach, gizzard and intestine, which belong to the order Spirurida — 

 an order which contains only parasitic forms. All these worms require 

 an intermediate host in order to complete their life-cycle. Oxyspirura 

 mansoni, which has been chiefly recorded from game birds and domestic 

 poultry, lays its eggs in the eye of the bird and they are subsequently 

 washed down the tear ducts and swallowed, eventually passing out of 

 the bird's body with its droppings. Cockroaches — and possibly other 

 insects — which are notoriously "dirty" feeders, ingest the eggs. About 

 two months later mature larvae are present in the insect. Sometimes 

 they are encysted in the fatty tissues and along the alimentary canal and 

 at other times free in the legs or body cavity. When the cockroach is 

 eaten by a susceptible bird the larvae are freed in the crop. From there 

 they migrate up the oesophagus and through the tear duct leading from 

 the nose to the bird's eye. Larvae may reach the eye only twenty 

 minutes after the infected cockroach has been swallowed. A related 

 species, 0. sygmoidea, is found in crows and rooks. 



The blood red proventriculus worms ( Tetrameres) live in the glands 

 of the stomach. The females are globular and fit snugly inside the glands, 

 but the males, which are almost microscopical in size, have the 

 typical nematode shape. They often remain attached to the surface of 

 the stomach wall and only penetrate inside the glands for the purpose of 

 copulation. One species, Tetrameres fissipinus, is found in various wild 

 birds in Britain, chiefly in goosander, pochard, coot, grebes and other 

 aquatic feeders. In this case a number of different intermediate hosts 

 are used. Those favoured are the water fleas {Daphnia pulex), and 

 fresh water shrimps {Gammarus pulex) , but earthworms, grasshoppers and 

 various other insects are used by the species parasitising poultry. 



Another common parasite found in the proventriculus of wild birds, 

 especially raptorials, is Acuaria laticeps. It is reported from the kestrel, 

 peregrine falcon, short-eared owl and barn-owl in Britain. Other 

 species of the same genus are found in swallows and martins, another 

 from wood-peckers, herons, and crows (including nutcrackers), and 

 shrikes. The various species are often characteristic of one family of 

 birds. The wood-louse [Armadillium vulgare) is the intermediate host for 



