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 
spirochete might be hereditary in mosquitoes. 
A spirochete was found to be an abundant parasite of mosquito larve by 
Jaffé. It was described by him as Spirocheta 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 larve 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 Spirocheta 
occurs in mosquitoes in great numbers. 
The Gregarinz 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 larvee at Secunderabad. Léger 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 
Aédes calopus. 
The French Commission at Rio de Janeiro, in its first memoir, gave a descrip- 
tion of a microsporidian parasite of the yellow-fever mosquito which they 
called Nosema stegomyie 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. Larve carrying the 
parasite are easily recognized from the beginning of their development by a 
microscopical examination. The 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 larve 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 larve 
by taking the spores of the Nosema from other larve 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 
