PARASITES OF SIMULIUM LARVAE 45 
one or more colonies. Large numbers of the larvae of this, and 
those of an undescribed species were parasitised by Microspor- 
idians. I have published a short account (’11) of the appearance 
of the infected larvae, and of the external structure of the spores 
of the species which I found. At the time of discovery all the 
forms had sporulated, so further details could not be given. By 
the middle of May all the larvae of the generation under observa- 
tion had pupated and hatched, and during the summer few larvae 
were to be seen in any of the streams. Only in a few places 
could I find an isolated specimen of what I have since found to 
be the hitherto undescribed larva of Simulium bracteatum Coq. 
On October 1 I resumed my search for Simuliid larvae, 
hoping to find the early stages of the parasites. A number of 
isolated larvae were observed in most of the streams visited, 
and it was not long before I found evidence of Microsporidian 
parasites. 
The larvae observed in the streams during the fall of 1911 are 
as follows: 
S. bracteatum; most numerous, occurring in all streams in 
which any larvae were found, though always living a solitary 
life. §. vittatum; very few specimens found in one stream. S. 
hirtipes; not found till the beginning of November after which 
it was common in some localities. 
By the middle of November collecting became extremely diffi- 
cult as the streams were filled with fallen leaves which had to 
be removed almost one by one, and examined for larvae, as the 
latter appeared to prefer them to the stones. 
DESCRIPTION: OF LARVA AND PUPA OF S. BRACTEATUM COQ. 
The adult of this species was described by Coquillett in 1898 
from specimens taken at Cambridge, Massachusetts, about seven 
miles from the locality in which I took larvae and pupae which 
yielded adults agreeing in all details with his description. 
Larva: plate 1, figs. 1 to 7. The mature larva is 6 mm. long 
and is of a somewhat brownish color. The cephalic fans have 
about fifty rays which are provided with very short internal 
cilia, all of which are of the same length. The antennae (fig. 
