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R. B. JACKSON
If
The wings of the Anopheline are usually ornamented with light and dark markings, but one of the local Anophelines A. aitkeni has plain wings like a Culicine. Its larvæ are found in shady pools in the hill streams. the antennæ of this mosquito are examined the sex can be determined and the nature of the palps will indicate that it is an Anopheline, the resting position will also confirm this. A Culicine with spotted wings exists in Hong Kong, it is called Culex mimeticus, from its resting position it can be seen that it is not an Anopheline, which can be further verified by examination of the antenna and palps, and the fact that the abdomen has pale cross bands. No Anopheline with banded abdomen exists in the
Colony.
Anopheline mosquito
Culicine mosquito
Diagrams of Resting positions.
Males of C. fatigans whilst resting on a mosquito curtain somewhat resemble Anophelines in their posture and appearance but the banded abdomen will indicate that they are not Anophelines as well as an examination of the palps and proboscis.
LL
a
Apart from the diseases which they carry, mosquitoes can cause serious nuisance as biting pests. Neighbouring unoccupied houses are fruit- ful sources of breeding if they are not properly looked after, also houses in process of erection or demolition on account of the careless habits of the workmen engaged on the task. Such breeding places have already been indicated. In dealing with a mosquito nuisance numerous samples of the offending insects should be captured in test tubes, or appliances for the purpose. Investigations should be made of all likely collections of water in the neighbourhood and when the larva are obtained they should be hatched out " and a comparison made between the mosquitoes thus obtain- ed and those already caught this will serve as an indication as to whether we are on the right track or not, as a good many kinds of mosquitoes either do not enter houses at all or else so infrequently that they do not constitute a nuisance. For all hatching out purposes a sieve such as is used for sifting rice, flour, etc. can be obtained at trifling cost. The side opposite the gauze should be covered with a piece of mosquito netting: a hole is then made with an auger in the woodwork of the sieve so as to enable the neck of a bottle (beer?) just to pass through. The bottle should be thoroughly cleaned and the larva with the corresponding water introduced. It is then passed through the hole in the sieve, Such mosquitoes as hatch out fly up from the bottle into the sieve and cannot escape. The bottle should stand in a saucer of water so that ants cannot make their way to the imprisoned mosquitoes.
The Hong Kong Naturalist.
A Brief Account of Mosquitoes
213
Yellow fever, formerly the scourge of the West Indies, and South America, is carried by a mosquito. In Hong Kong the following diseases are transmitted by these insects,-Malaria, human filariasis, canine filariasis, and dengue fever.
In the blood of a patient suffering from malaria certain bodies known as malarial parasites are found in the red blood corpuscles; these parasites are either asexual or sexual. The asexual parasites split up (after attaining full growth) into groups of smaller parasites, which in turn enter a fresh red blood corpuscle and continue the cycle. If there were only asexual parasites then these would die when their host died. The asexual parasites when present in sufficient numbers cause fever, but another form of the parasite is found in the blood-sexual parasites. When the Anopheline imbibes the blood of a person containing such parasites in sufficient numbers and pro- portions, the male and female unite in the stomach of the mosquito and result in the formation of little cysts which grow out from the stomach wall. In their early stages grains of pigment are found in these cysts, as the cysts grow larger the pigment is not so obvious: the cyst wall gets thicker and the cyst becomes full of little spindle-shaped bodies called sporozoites. In time the cyst wall bursts, the sporozoites are liberated and the majority make their way into the salivary glands of the insect. The cysts and sporozoites can only be seen with high powers of a good microscope. In some stomachs When twenty to twenty-five cysts have been observed, in others one or two. an infected mosquito sucks the blood of a person these sporozoites make their way from the salivary glands into the wound and infect him or her with malaria.
In Hong Kong the Anopheline larvæ most frequently encountered are those of A. maculatus, A. minimus, A. hyrcanus: those of A. maculatus being by far the most numerous and readily obtainable at all times. This is not the case with the larva of Anopheles minimus which recent researches made in the Malaria Bureau Hong Kong, have shown to be a most danger- ous mosquito,
In order to ascertain which are the dangerous species it is necessary to capture them from a place where malaria abounds, bring the catch to the Laboratory and examine them for infection, The mosquitoes are killed with chloroform and the salivary glands and stomach dissected out. The salivary glands are examined for the sporozoites (already mentioned) and the stomach for cysts.
:
The habits of Anophelines vary considerably some species after par- taking of a hearty blood meal do not tarry but take their departure, others remain in the building after feeding, such as A. minimus, which can be caught in the day time in a certain type of habitation close to their breeding grounds. The following device is in use for obtaining nocturnal vsitors: a man sleeps in a room on a camp bed provided with a mosquito net, outside this is a large mosquito net supported on four poles fitting into large wooden discs. The large mosquito net is provided with openings which can be closed by flaps the flaps are left open and the catcher withdraws to the shelter of the camp bed and its net. From time to time he gets up, lets down the
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