68 
THE PERSISTENCE OF BACILLUS PYOGYANEUS IN PUPAE 
AND IMAGINES OF MUSGA DOMESTIGA RAISED FROM 
LARVAE EXPERIMENTALLY INFECTED WITH THE 
BACILLUS. 
By A. W. BACOT, F.E.S., 
Loughton, Essex. 
In the course of an inquiry into the relation between the bionomics 
of certain insects and epidemic disease upon which I am engaged, the 
following question suggested itself to me. In the event of a larva 
becomiug bacterially contaminated by means of its food, is it possible 
that the resulting pupa and imago will still be infected ? The only 
previous work bearing upon this question with which I am acquainted 
is that of Faichnieh who writes: 
“ On Aug. 12th, 1909, three ounces of faeces, containing B. typhosus, 
were thrown on a box of earth and covered with a wire cage and about 
thirty flies were let loose inside. These flies all died in a day or two, 
but on Aug. 26th one fly hatched ; on Aug. 27th 12 flies hatched. 
On this same day, after the flies were hatched, the box of earth was 
replaced by an earthenware plate which had previously been washed in 
a solution of 1 in 500 perchloride of mercury: sugar and water as food 
in separate porcelain saucers were also introduced and the wire cover 
was changed for a bell-shaped mosquito net. On Aug. 26th one fly one 
day old was transfixed with a red-hot needle after chloroforming it, 
flamed, and put into a bottle of sterile salt solution. It was shaken 
up and 1 c.c. of this solution was put into McConkey broth, which 
remained unchanged in 48 hours. After this the fly was ci'ushed with 
a sterile glass rod and a drop plated ; B. typhosus was found. On Aug. 
27th four flies, each one day old, were singed and examined in the 
same way. The control in McConkey was negative, but from the 
crushed flies B. typhosus was separated. This process was repeated on 
Sept. 3rd, 6th, 10th, and 13th, twice all but one of the last named gave 
^ Faichnie, N. (1909). Bacillus typhosus in flies. Journ. Roy. Army Med. Corps xni. 
580-585, 672-675. 
