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A PROTOZOON PATHOGENIC TO MOSQUITO LARVAE. 
By W. A. LAMBORN, M.R.C.S., L.R.C.P., 
Medical Entomologist, Federated Malay States. 
(Malaria Bureau , Kuala Lumpur.) 
A batch of twenty-nine larvae of Stegomyia scutellaris Walker, were collected 
on 24 July 1920 from an old earthenware pot found in a Malay’s garden. It was 
at once seen, even with the unaided eye, that many, some considerably paler 
than others, were characterised by a pearly-white opalescence of the tracheal 
gills at the hinder end of the body. 
On microscopic examination it was found that the appearance was due to 
the presence of a large number of protozoa, which, though in most cases 
restricted to the gills, had in the paler larvae pervaded the body cavity, and 
the head 6ven to the interior of the antennae. 
The protozoa, which were under ordinary conditions pear-shaped and of 
considerable size, were usually to be seen careering most actively up and down 
within the gill as if seeking a point of exit from the larva, but in some cases 
were packed so tightly as to distend the gill. They were then immobile and 
spherical. One gill only w r as usually so distended, sometimes tv r o, and 
occasionally three and four, but invariably v r hen one gill showed the parasites 
in large numbers, the others showed them to a less extent. 
It was almost impossible to form any correct estimate of the number of 
organisms present in any one gill. One hundred and fifty-seven v r ere counted 
in a gill moderately packed with them, and in a gill fully distended it is probable 
that double that number might be present. 
When in such cases a breach of surface of one of the gills w T as made with 
a fine needle a large number of the protozoa came out and raced about wildly 
under the field of the microscope, and it could then be determined that they 
were provided with flagella. 
Evidence of their pathogenicity was afforded by the death in the course of 
a few r days of the entire original brood of larvae. Some tv r o pr three, which had 
shown but few of the parasites, did indeed pupate, and parasites w r ere seen 
moving slowly within, but none afforded imagoes. 
Within a day or two after the death of a larva most of the parasites had 
left it, though a small number, spherical and probably encysted, remained 
aggregated together. 
