PARASITES OF SIMULIUM LARVAE 83 
branched. ‘This attained a length of 20 to 30u, when it assumed 
a necklace-like form, after which it disintegrated without appar- 
ent further development or function. The infected larvae pupated 
and the parasite was present in the adult. In 1908 Lutz and 
Splendore also described briefly a species from the adults of 
Stegomyia fasciata which they named Nosema stegomyiae. The 
size of the spore was approximately that given by Simond and 
it is quite possible that this is the same species. 
Hesse (’04) described a species, Thelohania legeri, parasitic 
in the larvae of the malarial mosquito, Anopheles maculipennis 
Meig. The fat body of these larvae was the seat of infection, as 
in the case of Simulium. There were two types of spores present, 
viz., microspores, 8 x 4u, and macrospores, 12 x 5u. The filament 
was readily evaginated by the use of iodine. Although he did 
not find the parasites present in any adults he states that it is 
doubtless to be found in this stage, for the host does not. suffer 
in any way from the effects of the parasite. 
In these two cases the parasites were not, as far as the observa- 
tions show, in any way detrimental to their host. It must, 
however, be borne in mind that neither Nosema nor Thelohania, 
which are both genera of the family Nosematidae, form such 
large masses.of parasitic material as Glugea, and that in the 
descriptions of these two cases there is no mention of the parasite 
causing the body of its host to be in any way distended. This 
fact would surely not have been omitted had the effect been as 
marked as in the case of the Simulium larvae. 
In the parts of the stream where the parasites were most 
abundant I collected all the pupae I could find. These were 
sectioned, or dissected, but in no case could signs of any stage 
of the parasite be detected. When healthy and parasitised larvae 
were brought together into the laboratory the healthy larvae 
always lived for a much longer time than the parasitised individ- 
uals, and in several of the latter death. was apparently caused 
by the skin rupturing, when the mass of parasitic material pro- 
truded through the rent thus made. 
Mature larvae turn brown a little before pupation and the 
histoblasts of the pupal respiratory filaments blacken (pl. 6, fig. 
