lyO FLEAS, FLUKES AND CUCKOOS 



mourning-doves {^enaidura carolinensis) . Over 500 different species of 

 birds have been recorded as hosts. The only known insect carriers, in 

 which the sexual cycle occurs, are louse-flies (Hippoboscidae). 



In Haemoproteus the adult gametocyte encircles the nucleus of the 

 red blood corpuscles like a halter. This characteristic stage induced an 

 early worker to bestow the name Halteridium upon the parasite — a name 

 by which the group is still often known. In the case of this genus and 

 Leucocytozoon the only forms of the parasite which are found in the red 

 blood cells are the gametocytes. For this reason these two genera, un- 

 like the malarial parasites, cannot be transmitted in the laboratory 

 from bird to bird by injection of blood. Transmission occurs only as a 

 result of a bite by an infected insect carrier. The stages of the asexual 

 cycle (schizogony) are passed in the endothelial tissues. Some author- 

 ities have consequently divided off the two genera Leucocytozoon and 

 Haemoproteus from Plasmodium and placed them in a separate family, 

 Haemoproteidae. 



Other Sporozoa 



Another group of Sporozoa, Toxoplasma, which infects the white 

 blood corpuscles and various tissues, has been recorded from many wild 

 birds, including the English sparrow in the United States. It has been 

 found in two captive squirrels in this country but has not been studied 

 in birds. Haemogregarines and Piroplasms, which are also parasites in 

 the blood of avian hosts, may eventually be found in British wild 

 birds. Both groups have been recorded from wild mammals in this 

 country. 



Glass Mastigophora (Flagellata) 



The Protozoa which are included in this class are known as flagel- 

 lates, for, typically, they possess one or more flagella. Each flagellum 

 consists of a fine whip-like outgrowth which is capable of lashing or 

 rippling movements, by means of which the organism is enabled to 

 progress through the liquid medium in which it lives. Sometimes 

 flagella are used as organs of attachment rather than locomotion. 



The majority of Mastigophora have a single nucleus. They are 

 chiefly free-swimming and many of them live in the body fluids of 



