160 MOSQUITOES OF NORTH AMERICA 



of birds, conjugate and undergo sporogeny in mosquitoes. Before leaving these 

 blood-parasites it should be stated, however, that Dr. Fritz Schaudinn, in 1904, 

 expressed his belief that the parasite of malaria and also a trypanosome and a 

 spirochaete might be hereditary in mosquitoes. 



A spirocha}te was found to be an abundant parasite of mosquito larvae by 

 Jaff6. It Avas described by him as SpirocJiMa culicis and is a relatively large 

 species, its length being from 10-20 microns. It occurs in the digestive tract 

 of the larva of an undetermined mosquito; in the vicinity of Berlin as many as 

 90 per cent of the larva? were found infested. Very rarely the parasite was also 

 found in the imago, in the malpighian tubes. Its mode of reproduction is un- 

 known. The Sergents have found a similar organism in the larva of Anopheles 

 maculipennis in Algeria. Patton has determined that in India Spirocliceta 

 occurs in mosquitoes in great numbers. 



The Gregarinjfi are perhaps the most abundant protozoan parasites of insects. 

 They have been observed as parasites of mosquitoes by various authors. Ronald 

 Ross found gregarines in mosquito larva? at Sccunderabad. Leger and Duboscq, 

 in Corsica, found a gregarine, which they assign to Diplocystis, in a mosquito 

 larva. The French investigators at Rio de Janeiro found gregarines in adult 

 A'edes calopus. 



The French Commission at Rio de Janeiro, in its first memoir, gave a descrip- 

 tion of a microsix)ridian parasite of the yellow-fever mosquito which they 

 called Nosema stcgomyicE and frequently met with in this mosquito. In their 

 early researches the manner by which the mosquito becomes infected with this 

 parasite escaped them, but later they determined that the ordinary method is by 

 heredity, and this is stated in their second memoir, published in the Annals of 

 the Pasteur Institute, vol. 20, January, 1906. They show that with females 

 strongly infected with Nosema these reach the ovary and penetrate the eggs. 

 The egg parasitized in this way does not always die, and when it develops with 

 the spores in its interior it gives birth to an infested larva. Larvae carrying the 

 parasite are easily recognized from the beginning of their development by a 

 microscopical examination. Tlie parasite attacks particularly the transparent 

 vesicles situated near the anus, and in the interior of these vesicles they can be 

 distinguished either in the developing stage or the sporulating stage. Later the 

 digestive tube and the other organs are infected, and the larva is killed by the 

 development of the parasite. The mortality of larvae brought about by the 

 parasite appeared to be considerable, but there was almost none with the perfect 

 insect. The investigators were able to bring about a direct infection of larvte 

 by taking the spores of the Nosema from other larvae or from adult mosquitoes 

 and mixing them with their food. They remark that this is not surprising, since 

 with Lepidoptera, parasites of the same group are easily transmissible to cater- 

 pillars by the ingestion of spores, while hereditary transmission occurs at the 

 same time. The occurrence of this parasite in the yellow-fever mosquito has 

 no relation with the transmission of yellow fever; but the investigators thought 

 the knowledge of its hereditary propagation none the less interesting, and it 

 induced them to carry out studies concerning the possibility of the hereditary 



