326 Lesions Produced by ike Bite of the Black-fly 
Summary 
In order to bring the results of the foregoing studies together, 
the author appends the following resume of the clinical data pre¬ 
sented in the first paper. 
The black-fly, Simulium venustum , inflicts a painless bite, with 
ecchymosis and haemorrhage at the site of puncture. A papulo¬ 
vesicular lesion upon an urticarial base slowly develops, the full 
course of the lesion occupying several days to several weeks. Marked 
differences in individual reaction occur, but the typical course in¬ 
volves four stages. These are, in chronological order, the papular 
stage, the vesicular or pseudovesicular, the mature vesico-papular or 
weeping papular stage and the stage of involution terminating in a 
scar. The papule develops in from 3 to 24 hours. The early pseudo¬ 
vesicle develops in 24 to 48 hours. The mature vesico-papular lesion 
develops by the third to fifth day and may last from a few days to 
three weeks. Involution is marked by cessation of oozing, subsidence 
of the papule and sear-like changes at the site of the lesion. The 
symptoms accompanying this cycle consist of severe localized or 
diffused pruritus, with some heat and burning in the earlier stages 
if the oedema is marked. The pruritus appears with the pseudo¬ 
vesicular stage and exhibits extraordinary persistence and a marked 
tendency to periodic spontaneous exacerbation. The flies tend to 
group their bites and confluence of the developing lesions in such 
cases may result in extensive oedema with the formation of oozing 
and crusted plaques. A special tendency on the part of the flies 
to attack the skin about the cheeks, eyes and the neck along the 
hair line and behind the ears, is noted. In these sites inflammation 
and oedema may be extreme. 
A distinctive satellite adeonpathy of the cervical glands develops 
in the majority of susceptible persons within 48 hours after being 
bitten in the typical sites. This adenopathy is marked, discrete 
and painful, the glands often exquisitely tender on pressure. It 
subsides without suppuration. 
Immunity may be developed to all except the earliest manifesta¬ 
tions, by repeated exposures. Such an immunity in natives of an 
infested locality is usually highly developed. There are also ap¬ 
parently seasonal variations in the virulence of the fly and variations 
in the reaction of the same individual to different bites. 
Constitutional effects were not observed but have been reported. 
