PARASITES OF SIMULIUM LARVAE 65 
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of S. venustum and §. ochraceum. In a further discussion of 
these forms in 1908, they regarded them all as varieties of one 
species, which they designate as Nosema simulii. The locality 
in which this presumably South American species was taken is 
not stated. In asubsequent paper by Lutz (’09) on the Simulidae 
of Brazil, he mentions the presence of Nosema sp. in the larvae 
but gives no details. The only other account seems to be the 
the one which I published in 1911. In that I described the 
_ external appearance of the spores of several undetermined species 
which infest the larvae of 8S. hirtipes and an undescribed Simulium 
larva common in the streams in the vicinity of Boston, Massa- 
chusetts. 
During the fall of 1911 I found three further well-marked 
forms in the Simulium larvae of the same locality. One of these 
resembles the form described by Léger. His description, how- 
ever, is very short and is not accompanied by figures. The fila- 
ment of the American species is about twice as long as that of 
G. varians. Another form resembles somewhat Lutz and Splen- 
dore’s figures of [Nosema] Gluguea simulii but here again the 
filament of the latter species is about six times the relative length 
of the American species. Probably, with a fuller account of 
the development of these exotic species, other differences would 
be found, especially in the case of G. varians, for it is unlikely 
that the same species of Microsporidian should occur in both 
hemispheres parasitising larvae of such specialized and confined 
habitats as those of Simulium. It is true that this genus of 
Diptera is cosmopolitan and is recorded by Griinberg (’07) as 
occurring even in Lapland and Greenland, but since none of 
the European species has been recorded from America it is very 
unlikely that their parasites, which also occur in both hemispheres, 
should be but varieties of the same species. 
The Microsporidian species under consideration apparently 
all fall into the genus Glugea as defined by Thélohan (’91). In 
1892 Henneguy erected the genus Thelohania of which I have 
been unable to obtain the original description. The sporula- 
tion of the species I have described as Glugea bracteata is 
typical of the genus Thelohania according to Gurley’s (’94) 
JOURNAL OF MORPHOLOGY, VOL. 24, No. 1 
