Ronald Ross Nobel Lecture

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legs tilted on the back. Breeding mostly in pots of water. Larvae floating head

downwards and possessing short stumpy breathing tubes. Eggs black, oval,

and laid separately.

(b) Grey mosquitoes (now recognized as belonging to the genus Culex, Linn.

as defined by Theobald). Back barred with transverse brown and white stri-

pes. Legs and wings plain. Biting somewhat timidly, mostly at night. Resting

with abdomen hanging towards surface of attachment. Breeding mostly in

wooden tubs, ditches, garden cisterns, and drains. Larvae floating head down-

wards and possessing long breathing tubes. Eggs elongated and somewhat

lanceolate and laid simultaneously in "rafts".

I had found mosquitoes of the same genera, though possibly of different

species, at Bangalore and at several spots in the Nilgherry Hills; and also at

Bombay, Poona, and Madras during short visits made to these cities in con-

nection with my sanitary duties at Bangalore. I remembered also to have seen

similar insects in Burma and the Andamans; so that it was reasonable to sup-

pose that they constituted the common or ordinary kinds of mosquitoes in

India. The new mosquitoes which I now and subsequently met with, and

named dappled-winged mosquitoes, were evidently of quite another genus to

the foregoing, and were distinguished by me by the following characteristics:

(c) Dappled-winged or spotted-winged mosquitoes (now recognized as belong-

ing to the genus Anopheles, Meig.). Body, legs, and proboscis marked brown

and white, or dark and light brown. Wings with several dark blotches on or

near the anterior nervure. Resting with abdomen pointed outward from the

surface of attachment. Body more elegant, and shaped like that of a humming-

bird moth. Breeding mostly in natural pools of water on the ground. Larvae

floating flat on the surface of the water like sticks, and possessing no breathing

tube at all. Eggs laid singly; cohering in triangular patterns, and shaped like an

ancient boat with raised prow and stem, and surrounded with a membrane

which - when the egg is seen in profile - gives the appearance of a bank of

oars to the boat.

In the spotted-winged mosquitoes which I now found at Secunderabad I

noticed at once the general difference of shape, the peculiar attitude of the in-

sects when at rest, the marks on the wings, and the appearance of the eggs (as

seen within the body of the female when dissected); but the larvae could not

be studied until later.* The adults were very delicate, pale-brown creatures,

which by common consent seemed scarcely to bite man, though they were

* It was principally my assistant, Mahomed Bux, who ascertained, as a general rule, the

attitude of the larvae.

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numerous enough to have caused much irritation had they done so. They

swarmed in my own quarters, but seldom bit me. They abounded also in the

houses of the other officers of the regiment, who, with their families had re-

mained quite free from malarial fever. Consequently I was not disposed to

think that they had anything to do with the disease. On the other hand the

grey mosquitoes swarmed in the barracks, but were much less numerous in

the officer’s quarters (situated some hundreds of yards to leeward of the bar-

racks). Suspicion therefore first attached to the latter variety.

I determined, however, not to be swayed by such considerations, but to

make a most complete and exhaustive test of all the varieties which I could

procure - even at the cost of repeating much of my old negative work, during

which, laborious as it was, I may have overlooked the object I was in search of.

A number of natives were employed to collect larvae from far and wide round

the barracks. These larvae were kept in separate bottles, and when the adult

insects appeared they were released within mosquito nets in which the patients

were placed. The insects were applied sometimes during the day in a darkened

room; and were sometimes fed all night. After feeding, the gorged insects

were collected in small bottles containing a little water and were kept for

several days before being dissected. The procedure was therefore the same as

before; but now, in order to ensure at least definite negative results, redoubled

care was taken; almost every cell was examined; even the integument and legs

were not neglected; the evacuations of the insects found in the bottles, and the

contents of the intestine were scrupulously searched; at the end of the first

examination staining reagents were often run through the preparation, and it

was searched again with care. The work, which was continued from 8 a.m.

to 3 or 4 p.m. with a short interval for breakfast, was most exhausting, and so

blinding that I could scarcely see afterwards; and the difficulty was increased

by the fact that my microscope was almost worn out, the screws being rusted

with sweat from my hands and forehead, and my only remaining eye-piece

being cracked, while swarms of flies persecuted me at their pleasure as I sat

with both hands engaged at the instrument. As the year had almost been rain-

less (it was the first year of plague and famine) the heat was almost intolerable,

and a punkah could not be used for fear of injuring the delicate dissections.

Fortunately my invaluable oil-immersion object-glass remained good.

Towards the middle of August I had exhaustively searched numerous grey

mosquitoes and a few brindled mosquitoes. The results were absolutely nega-

tive; the insects contained nothing whatever. Then, I think for the first time,

I began to feel that the long quest had been in vain and that a flaw existed some-

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