750 ORDER: MICROSPORIDIIDA 



These are ovoid in shape, and measure 5-5 to 6 by 3-5 to 4 microns. 

 The polar filament is 110 microns in length. Occasionally, the pansporo- 

 blast gives rise to only four sporoblasts, which produce correspondingly 

 larger spores, measuring 8 to 8-5 by 4-5 to 5-5 microns. The polar filament 

 in these cases reaches a length of 200 microns. 



The same author (19246) describes as T. obesa a parasite of the fat body 

 of an anopheline {A. quadrimaculatus ?) larva. The pansporoblast, which 

 gives rise to a group of eight spores, is 9 to 10 microns in diameter. The 

 fixed and stained spore measures 4 to 4-5 by 3 to 3-5 microns. 



Another species recorded by this author (19246) is T. pyriformis from 

 the fat body of larvae of A. crucians or A. quadrimaculatus. The fixed 

 and stained spore measures 3-5 to 4 by 2 to 2-8 microns. In the fresh 

 condition it appears considerably larger, and measures 4-8 to 5-4 by 2-7 

 to 3 microns. 



Kudo (1920, 1921) described as T. magna a microsporidian of the 

 larvae of C. 'pvpiens and C. territans in North America. Later (19246) 

 he transferred it to the genus Stempellia (Fig. 313). It occurs in the cells 

 of the adipose tissue, and the larvae were heavily infected. The parasite 

 multiplies by binary fission or by schizogony. Finally, a division of a 

 parasite into four cells, which remain connected together, takes place. 

 A further division of each of these may occur. The resulting cells are 

 sporoblasts, which develop into spores. The spore measures 12-5 to 16-5 

 by 4 to 4-6 microns. The extruded filament may reach a length of 350 

 to 400 microns. 



Two other species of Thelohania are recorded by Kudo (19246) from 

 Culex leprincei of North America. One of these is named T. rotunda. 

 The spore is broadly ovoid or sub-spherical, and when fixed measures 

 2-5 to 3 by 2-3 to 2-7 microns. The other, T. minuta, has an ovoid spore 

 measuring when fresh 3-5 to 3-7 by 2-4 to 2-7 microns, and when fixed 

 2-5 to 3-3 by 1-5 to 2 microns. Both occur in the adipose tissue of the 

 larvae, while T. minuta has been found in the pupae also. 



The writer has seen a Thelohania which was discovered by MacGregor 

 in larvae of Aedes (Ochlerotatus) nemorosus in England. The fresh spores 

 measured 6 to 7 by 4 to 4*5 microns. The parasite occurred chiefly in the fat 

 body, and appeared to be specific for the larvae of this particular mosquito, 

 as the larvae of other mosquitoes, including other species of the same genus, 

 in the pond at the same time were not infected. Attempts to infect larvae 

 of 0. nemorosus from another locality and larvae hatched in the laboratory 

 failed, though enormous numbers of the spores were ingested. No infec- 

 tion of the body cavity took place. In the pond, in which at one time 

 early in March at least 50 per cent, of the larvae of this species were infected, 

 the infection gradually died out during the course of one month, though 



