TRANSFORMATIONS OF BUFFALO GNATS. 27 
INSECT ENEMIES AND PARASITES. 
The larvae of Simulium are often parasitized by nematode worms 
of the genus Mermis, specimens of which have been found by the 
writer measuring 12 mm. in length. These were found in larvae of 
JS. venustum, coiled around the intestines, and extended from near the 
caudal end to the thorax. The specimens that attained the greatest 
length were found singly, but as many as four have been found in 
individual larvae. According to Strickland (1911), 1 the Mermis 
retard the development of the pupal and adult histoblasts, cause 
the death of the larvae, and escape through punctures made in the 
epidermis. He also states that in the vicinity of Boston, Mass., 
Mermis was found parasitizing larvae only during the spring, and 
that there is a seasonal variation of parasitism. The writer, while in 
South Carolina, found species of Mermis parasitizing larvae from 
May until late in October, and these larvae seemed to have developed 
the pupal histoblasts to a much greater extent than is estimated by 
Strickland. The larvae are also heavily attacked by glugeid and 
gregarine species of Myxosporidia. 
The writer has found the larvae being attacked by species of 
Hydropsyche in Illinois and South Carolina. Dr. Howard (1888) * 
also mentions this fact in his article on a species of Simulium at 
Ithaca, N. Y., and gives a fuller account in the Annual Report of the 
U. S. Commissioner of Agriculture for 1886, page 510. Species of 
minnows attack the larvae frequently, and Eiley 2 mentions that the 
small fishes of the family Cyprinidae also feed on them. 
The pupae, so far as is known, are not parasitized by Mermis or 
Myxosporidia. The adults have been found by the writer at Spar- 
tanburg, S. C, to be frequently parasitized by nematode worms of 
the genus Mermis, which were usually found singly. In one in- 
stance three of the worms were found in a female S. venustum. 
The same number were found in a female of S. bracteatum. They 
were situated in the abdomen, coiled around the Malpighian tubes 
and intestines, and in some cases extended into the thoracic region. 
The vitality of these specimens infested by the Mermis seemed to be 
seriously affected, though they lived for some time, 31 hours being 
the minimum and 72 the maximum period. All of these specimens 
thus parasitized were reared from pupae, with the exception of one 
adult female of S. hracteatum, which was taken flying around a lamp 
at night. No adults taken biting on animals were ever found to 
contain Mermis. 
1 See Bibliography, p. 35. 
2 Riley, C. V. Report of the Entomologist. In Rept. U. S. Comr. Agr. f. 1886, p. 459- 
592 (p. 510), 11 pi., 1886. 
